From 5a446c1ea9b829f291fe2d29b3ec7f1eabe8f26e Mon Sep 17 00:00:00 2001
From: Ferdia McKeogh <ferdia@mckeogh.tech>
Date: Wed, 21 Aug 2019 09:13:51 +0100
Subject: [PATCH 01/33] Fix `window.hashchange is not a function`

---
 src/librustdoc/html/static/main.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustdoc/html/static/main.js b/src/librustdoc/html/static/main.js
index 82d2c11b2497b..1f5a9447f46b3 100644
--- a/src/librustdoc/html/static/main.js
+++ b/src/librustdoc/html/static/main.js
@@ -344,7 +344,7 @@ if (!DOMTokenList.prototype.remove) {
             var set_fragment = function(name) {
                 if (browserSupportsHistoryApi()) {
                     history.replaceState(null, null, "#" + name);
-                    window.hashchange();
+                    highlightSourceLines(null);
                 } else {
                     location.replace("#" + name);
                 }

From cab607edcfe556343aa4fcb3de6229a790fc5e72 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 31 Aug 2019 18:34:50 -0700
Subject: [PATCH 02/33] Emit a single error on if expr with expectation and no
 else clause

---
 src/librustc_typeck/check/_match.rs           | 41 ++++++---
 src/test/ui/if/if-without-else-as-fn-expr.rs  |  6 --
 .../ui/if/if-without-else-as-fn-expr.stderr   | 83 ++-----------------
 src/test/ui/issues/issue-50577.rs             |  1 -
 src/test/ui/issues/issue-50577.stderr         | 15 +---
 5 files changed, 38 insertions(+), 108 deletions(-)

diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index efc37cc04b212..3983a3b820391 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -112,23 +112,36 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             self.diverges.set(pats_diverge);
-            let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-            all_arms_diverge &= self.diverges.get();
-
-            let span = expr.span;
-
-            if source_if {
+            let arm_ty = if source_if {
                 let then_expr = &arms[0].body;
                 match (i, if_no_else) {
-                    (0, _) => coercion.coerce(self, &self.misc(span), &arm.body, arm_ty),
-                    (_, true) => self.if_fallback_coercion(span, then_expr, &mut coercion),
+                    (0, _) => {
+                        let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+                        all_arms_diverge &= self.diverges.get();
+                        coercion.coerce(self, &self.misc(expr.span), &arm.body, arm_ty);
+                        arm_ty
+                    }
+                    (_, true) => {
+                        if self.if_fallback_coercion(expr.span, then_expr, &mut coercion) {
+                            tcx.types.err
+                        } else {
+                            let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+                            all_arms_diverge &= self.diverges.get();
+                            arm_ty
+                        }
+                    }
                     (_, _) => {
+                        let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+                        all_arms_diverge &= self.diverges.get();
                         let then_ty = prior_arm_ty.unwrap();
-                        let cause = self.if_cause(span, then_expr, &arm.body, then_ty, arm_ty);
+                        let cause = self.if_cause(expr.span, then_expr, &arm.body, then_ty, arm_ty);
                         coercion.coerce(self, &cause, &arm.body, arm_ty);
+                        arm_ty
                     }
                 }
             } else {
+                let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+                all_arms_diverge &= self.diverges.get();
                 let arm_span = if let hir::ExprKind::Block(blk, _) = &arm.body.node {
                     // Point at the block expr instead of the entire block
                     blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span)
@@ -139,7 +152,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // The reason for the first arm to fail is not that the match arms diverge,
                     // but rather that there's a prior obligation that doesn't hold.
                     0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
-                    _ => (span, ObligationCauseCode::MatchExpressionArm {
+                    _ => (expr.span, ObligationCauseCode::MatchExpressionArm {
                         arm_span,
                         source: match_src,
                         prior_arms: other_arms.clone(),
@@ -153,7 +166,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if other_arms.len() > 5 {
                     other_arms.remove(0);
                 }
-            }
+                arm_ty
+            };
             prior_arm_ty = Some(arm_ty);
         }
 
@@ -185,11 +199,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         then_expr: &'tcx hir::Expr,
         coercion: &mut CoerceMany<'tcx, '_, rustc::hir::Arm>,
-    ) {
+    ) -> bool {
         // If this `if` expr is the parent's function return expr,
         // the cause of the type coercion is the return type, point at it. (#25228)
         let ret_reason = self.maybe_get_coercion_reason(then_expr.hir_id, span);
         let cause = self.cause(span, ObligationCauseCode::IfExpressionWithNoElse);
+        let mut error = false;
         coercion.coerce_forced_unit(self, &cause, &mut |err| {
             if let Some((span, msg)) = &ret_reason {
                 err.span_label(*span, msg.as_str());
@@ -200,7 +215,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             err.note("`if` expressions without `else` evaluate to `()`");
             err.help("consider adding an `else` block that evaluates to the expected type");
+            error = true;
         }, ret_reason.is_none());
+        error
     }
 
     fn maybe_get_coercion_reason(&self, hir_id: hir::HirId, span: Span) -> Option<(Span, String)> {
diff --git a/src/test/ui/if/if-without-else-as-fn-expr.rs b/src/test/ui/if/if-without-else-as-fn-expr.rs
index 15892de83854c..826371be35f45 100644
--- a/src/test/ui/if/if-without-else-as-fn-expr.rs
+++ b/src/test/ui/if/if-without-else-as-fn-expr.rs
@@ -3,7 +3,6 @@ fn foo(bar: usize) -> usize {
         return 3;
     }
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
 }
 
 fn foo2(bar: usize) -> usize {
@@ -11,7 +10,6 @@ fn foo2(bar: usize) -> usize {
         return 3;
     };
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
     x
 }
 
@@ -20,7 +18,6 @@ fn foo3(bar: usize) -> usize {
         3
     }
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
 }
 
 fn foo_let(bar: usize) -> usize {
@@ -28,7 +25,6 @@ fn foo_let(bar: usize) -> usize {
         return 3;
     }
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
 }
 
 fn foo2_let(bar: usize) -> usize {
@@ -36,7 +32,6 @@ fn foo2_let(bar: usize) -> usize {
         return 3;
     };
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
     x
 }
 
@@ -45,7 +40,6 @@ fn foo3_let(bar: usize) -> usize {
         3
     }
     //~^^^ ERROR if may be missing an else clause
-    //~| ERROR mismatched types [E0308]
 }
 
 // FIXME(60254): deduplicate first error in favor of second.
diff --git a/src/test/ui/if/if-without-else-as-fn-expr.stderr b/src/test/ui/if/if-without-else-as-fn-expr.stderr
index 06600b1cb9aea..b49c2aa6319df 100644
--- a/src/test/ui/if/if-without-else-as-fn-expr.stderr
+++ b/src/test/ui/if/if-without-else-as-fn-expr.stderr
@@ -1,14 +1,3 @@
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:2:5
-   |
-LL | /     if bar % 5 == 0 {
-LL | |         return 3;
-LL | |     }
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
   --> $DIR/if-without-else-as-fn-expr.rs:2:5
    |
@@ -24,20 +13,8 @@ LL | |     }
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:10:20
-   |
-LL |       let x: usize = if bar % 5 == 0 {
-   |  ____________________^
-LL | |         return 3;
-LL | |     };
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
-  --> $DIR/if-without-else-as-fn-expr.rs:10:20
+  --> $DIR/if-without-else-as-fn-expr.rs:9:20
    |
 LL |       let x: usize = if bar % 5 == 0 {
    |  _________-__________^
@@ -52,19 +29,8 @@ LL | |     };
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:19:5
-   |
-LL | /     if bar % 5 == 0 {
-LL | |         3
-LL | |     }
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
-  --> $DIR/if-without-else-as-fn-expr.rs:19:5
+  --> $DIR/if-without-else-as-fn-expr.rs:17:5
    |
 LL |   fn foo3(bar: usize) -> usize {
    |                          ----- expected `usize` because of this return type
@@ -78,19 +44,8 @@ LL | |     }
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:27:5
-   |
-LL | /     if let 0 = 1 {
-LL | |         return 3;
-LL | |     }
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
-  --> $DIR/if-without-else-as-fn-expr.rs:27:5
+  --> $DIR/if-without-else-as-fn-expr.rs:24:5
    |
 LL |   fn foo_let(bar: usize) -> usize {
    |                             ----- expected `usize` because of this return type
@@ -104,20 +59,8 @@ LL | |     }
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:35:20
-   |
-LL |       let x: usize = if let 0 = 1 {
-   |  ____________________^
-LL | |         return 3;
-LL | |     };
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
-  --> $DIR/if-without-else-as-fn-expr.rs:35:20
+  --> $DIR/if-without-else-as-fn-expr.rs:31:20
    |
 LL |       let x: usize = if let 0 = 1 {
    |  _________-__________^
@@ -132,19 +75,8 @@ LL | |     };
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error[E0308]: mismatched types
-  --> $DIR/if-without-else-as-fn-expr.rs:44:5
-   |
-LL | /     if let 0 = 1 {
-LL | |         3
-LL | |     }
-   | |_____^ expected usize, found ()
-   |
-   = note: expected type `usize`
-              found type `()`
-
 error[E0317]: if may be missing an else clause
-  --> $DIR/if-without-else-as-fn-expr.rs:44:5
+  --> $DIR/if-without-else-as-fn-expr.rs:39:5
    |
 LL |   fn foo3_let(bar: usize) -> usize {
    |                              ----- expected `usize` because of this return type
@@ -158,7 +90,6 @@ LL | |     }
    = note: `if` expressions without `else` evaluate to `()`
    = help: consider adding an `else` block that evaluates to the expected type
 
-error: aborting due to 12 previous errors
+error: aborting due to 6 previous errors
 
-Some errors have detailed explanations: E0308, E0317.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0317`.
diff --git a/src/test/ui/issues/issue-50577.rs b/src/test/ui/issues/issue-50577.rs
index bf892a8daa27f..f0f1dc6c28667 100644
--- a/src/test/ui/issues/issue-50577.rs
+++ b/src/test/ui/issues/issue-50577.rs
@@ -2,6 +2,5 @@ fn main() {
     enum Foo {
         Drop = assert_eq!(1, 1)
         //~^ ERROR if may be missing an else clause
-        //~| ERROR mismatched types [E0308]
     }
 }
diff --git a/src/test/ui/issues/issue-50577.stderr b/src/test/ui/issues/issue-50577.stderr
index 413c8c5c80b52..0c3ba2ea4f94d 100644
--- a/src/test/ui/issues/issue-50577.stderr
+++ b/src/test/ui/issues/issue-50577.stderr
@@ -1,13 +1,3 @@
-error[E0308]: mismatched types
-  --> $DIR/issue-50577.rs:3:16
-   |
-LL |         Drop = assert_eq!(1, 1)
-   |                ^^^^^^^^^^^^^^^^ expected isize, found ()
-   |
-   = note: expected type `isize`
-              found type `()`
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
-
 error[E0317]: if may be missing an else clause
   --> $DIR/issue-50577.rs:3:16
    |
@@ -23,7 +13,6 @@ LL |         Drop = assert_eq!(1, 1)
    = help: consider adding an `else` block that evaluates to the expected type
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0308, E0317.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0317`.

From aae2b245e4c3958ca37d6eaa58b89d955d0b66e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 31 Aug 2019 18:42:13 -0700
Subject: [PATCH 03/33] deduplicate code

---
 src/librustc_typeck/check/_match.rs | 40 ++++++++++++-----------------
 1 file changed, 17 insertions(+), 23 deletions(-)

diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index 3983a3b820391..63d059bdf2a80 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -112,36 +112,31 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             self.diverges.set(pats_diverge);
-            let arm_ty = if source_if {
+            let arm_ty = if source_if && if_no_else && i != 0 && self.if_fallback_coercion(
+                expr.span,
+                &arms[0].body,
+                &mut coercion,
+            ) {
+                    tcx.types.err
+            } else {
+                // Only call this if this is not an `if` expr with an expected type and no `else`
+                // clause to avoid duplicated type errors. (#60254)
+                let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+                all_arms_diverge &= self.diverges.get();
+                arm_ty
+            };
+            if source_if {
                 let then_expr = &arms[0].body;
                 match (i, if_no_else) {
-                    (0, _) => {
-                        let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-                        all_arms_diverge &= self.diverges.get();
-                        coercion.coerce(self, &self.misc(expr.span), &arm.body, arm_ty);
-                        arm_ty
-                    }
-                    (_, true) => {
-                        if self.if_fallback_coercion(expr.span, then_expr, &mut coercion) {
-                            tcx.types.err
-                        } else {
-                            let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-                            all_arms_diverge &= self.diverges.get();
-                            arm_ty
-                        }
-                    }
+                    (0, _) => coercion.coerce(self, &self.misc(expr.span), &arm.body, arm_ty),
+                    (_, true) => {} // Handled above to avoid duplicated type errors (#60254).
                     (_, _) => {
-                        let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-                        all_arms_diverge &= self.diverges.get();
                         let then_ty = prior_arm_ty.unwrap();
                         let cause = self.if_cause(expr.span, then_expr, &arm.body, then_ty, arm_ty);
                         coercion.coerce(self, &cause, &arm.body, arm_ty);
-                        arm_ty
                     }
                 }
             } else {
-                let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-                all_arms_diverge &= self.diverges.get();
                 let arm_span = if let hir::ExprKind::Block(blk, _) = &arm.body.node {
                     // Point at the block expr instead of the entire block
                     blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span)
@@ -166,8 +161,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if other_arms.len() > 5 {
                     other_arms.remove(0);
                 }
-                arm_ty
-            };
+            }
             prior_arm_ty = Some(arm_ty);
         }
 

From a9ce33c059d0a91fb12a79d75aa1a868d76bf6f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 1 Sep 2019 02:22:42 -0700
Subject: [PATCH 04/33] Account for arbitrary self types in E0599

---
 src/librustc/ty/context.rs                    | 18 +++++
 src/librustc_typeck/check/expr.rs             | 72 +++++++++++++------
 src/librustc_typeck/check/method/mod.rs       |  2 +-
 src/librustc_typeck/check/method/suggest.rs   |  9 +--
 src/librustc_typeck/check/mod.rs              |  2 +-
 .../no-method-suggested-traits.stderr         |  8 +++
 .../point-at-arbitrary-self-type-method.rs    |  9 +++
 ...point-at-arbitrary-self-type-method.stderr | 15 ++++
 ...int-at-arbitrary-self-type-trait-method.rs | 10 +++
 ...at-arbitrary-self-type-trait-method.stderr | 18 +++++
 src/test/ui/traits/trait-item-privacy.stderr  |  7 ++
 11 files changed, 144 insertions(+), 26 deletions(-)
 create mode 100644 src/test/ui/self/point-at-arbitrary-self-type-method.rs
 create mode 100644 src/test/ui/self/point-at-arbitrary-self-type-method.stderr
 create mode 100644 src/test/ui/self/point-at-arbitrary-self-type-trait-method.rs
 create mode 100644 src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr

diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index e240e0df8b948..f355e231914d2 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -2402,6 +2402,24 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_generic_adt(def_id, ty)
     }
 
+    #[inline]
+    pub fn mk_pin(self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        let def_id = self.require_lang_item(lang_items::PinTypeLangItem, None);
+        self.mk_generic_adt(def_id, ty)
+    }
+
+    #[inline]
+    pub fn mk_rc(self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        let def_id = self.require_lang_item(lang_items::Rc, None);
+        self.mk_generic_adt(def_id, ty)
+    }
+
+    #[inline]
+    pub fn mk_arc(self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        let def_id = self.require_lang_item(lang_items::Arc, None);
+        self.mk_generic_adt(def_id, ty)
+    }
+
     #[inline]
     pub fn mk_maybe_uninit(self, ty: Ty<'tcx>) -> Ty<'tcx> {
         let def_id = self.require_lang_item(lang_items::MaybeUninitLangItem, None);
diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
index a53fb12367d0e..efff8bcdacbcf 100644
--- a/src/librustc_typeck/check/expr.rs
+++ b/src/librustc_typeck/check/expr.rs
@@ -12,7 +12,7 @@ use crate::check::fatally_break_rust;
 use crate::check::report_unexpected_variant_res;
 use crate::check::Needs;
 use crate::check::TupleArgumentsFlag::DontTupleArguments;
-use crate::check::method::SelfSource;
+use crate::check::method::{probe, SelfSource};
 use crate::util::common::ErrorReported;
 use crate::util::nodemap::FxHashMap;
 use crate::astconv::AstConv as _;
@@ -775,35 +775,65 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // no need to check for bot/err -- callee does that
         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
 
-        let method = match self.lookup_method(rcvr_t,
-                                              segment,
-                                              span,
-                                              expr,
-                                              rcvr) {
+        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
+            if let Ok(pick) = self.lookup_probe(
+                span,
+                segment.ident,
+                new_rcvr_t,
+                rcvr,
+                probe::ProbeScope::AllTraits,
+            ) {
+                err.span_label(
+                    pick.item.ident.span,
+                    &format!("the method is available for `{}` here", new_rcvr_t),
+                );
+            }
+        };
+
+        let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr) {
             Ok(method) => {
                 self.write_method_call(expr.hir_id, method);
                 Ok(method)
             }
             Err(error) => {
                 if segment.ident.name != kw::Invalid {
-                    self.report_method_error(span,
-                                             rcvr_t,
-                                             segment.ident,
-                                             SelfSource::MethodCall(rcvr),
-                                             error,
-                                             Some(args));
+                    if let Some(mut err) = self.report_method_error(
+                        span,
+                        rcvr_t,
+                        segment.ident,
+                        SelfSource::MethodCall(rcvr),
+                        error,
+                        Some(args),
+                    ) {
+                        if let ty::Adt(..) = rcvr_t.sty {
+                            // Try alternative arbitrary self types that could fulfill this call.
+                            // FIXME: probe for all types that *could* be arbitrary self-types, not
+                            // just this whitelist.
+                            let box_rcvr_t = self.tcx.mk_box(rcvr_t);
+                            try_alt_rcvr(&mut err, box_rcvr_t);
+                            let pin_rcvr_t = self.tcx.mk_pin(rcvr_t);
+                            try_alt_rcvr(&mut err, pin_rcvr_t);
+                            let arc_rcvr_t = self.tcx.mk_arc(rcvr_t);
+                            try_alt_rcvr(&mut err, arc_rcvr_t);
+                            let rc_rcvr_t = self.tcx.mk_rc(rcvr_t);
+                            try_alt_rcvr(&mut err, rc_rcvr_t);
+                        }
+                        err.emit();
+                    }
                 }
                 Err(())
             }
         };
 
         // Call the generic checker.
-        self.check_method_argument_types(span,
-                                         expr.span,
-                                         method,
-                                         &args[1..],
-                                         DontTupleArguments,
-                                         expected)
+        self.check_method_argument_types(
+            span,
+            expr.span,
+            method,
+            &args[1..],
+            DontTupleArguments,
+            expected,
+        )
     }
 
     fn check_expr_cast(
@@ -1466,8 +1496,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let struct_variant_def = def.non_enum_variant();
             let field_names = self.available_field_names(struct_variant_def);
             if !field_names.is_empty() {
-                err.note(&format!("available fields are: {}",
-                                    self.name_series_display(field_names)));
+                err.note(&format!(
+                    "available fields are: {}",
+                    self.name_series_display(field_names),
+                ));
             }
         }
     }
diff --git a/src/librustc_typeck/check/method/mod.rs b/src/librustc_typeck/check/method/mod.rs
index a7e4f8e5c6289..1509c0f8a2196 100644
--- a/src/librustc_typeck/check/method/mod.rs
+++ b/src/librustc_typeck/check/method/mod.rs
@@ -245,7 +245,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         Ok(result.callee)
     }
 
-    fn lookup_probe(
+    pub fn lookup_probe(
         &self,
         span: Span,
         method_name: ast::Ident,
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index 440e7e5d0e314..72e6f59715960 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -69,12 +69,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         source: SelfSource<'b>,
         error: MethodError<'tcx>,
         args: Option<&'tcx [hir::Expr]>,
-    ) {
+    ) -> Option<DiagnosticBuilder<'_>> {
         let orig_span = span;
         let mut span = span;
         // Avoid suggestions when we don't know what's going on.
         if rcvr_ty.references_error() {
-            return;
+            return None;
         }
 
         let print_disambiguation_help = |
@@ -314,7 +314,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             _ => {}
                         }
                         err.emit();
-                        return;
+                        return None;
                     } else {
                         span = item_name.span;
                         let mut err = struct_span_err!(
@@ -529,7 +529,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     );
                 }
 
-                err.emit();
+                return Some(err);
             }
 
             MethodError::Ambiguity(sources) => {
@@ -573,6 +573,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 bug!("no return type expectations but got BadReturnType")
             }
         }
+        None
     }
 
     fn suggest_use_candidates(&self,
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index a80550486d627..2d9cacea68f31 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -3580,7 +3580,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     SelfSource::QPath(qself),
                     error,
                     None,
-                );
+                ).map(|mut e| e.emit());
             }
             result
         });
diff --git a/src/test/ui/impl-trait/no-method-suggested-traits.stderr b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
index d980d7cccadd5..002b60f9f258d 100644
--- a/src/test/ui/impl-trait/no-method-suggested-traits.stderr
+++ b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
@@ -49,6 +49,14 @@ LL | use foo::Bar;
 error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::boxed::Box<&char>>` in the current scope
   --> $DIR/no-method-suggested-traits.rs:32:43
    |
+LL |         fn method(&self) {}
+   |            ------
+   |            |
+   |            the method is available for `std::boxed::Box<std::rc::Rc<&mut std::boxed::Box<&char>>>` here
+   |            the method is available for `std::pin::Pin<std::rc::Rc<&mut std::boxed::Box<&char>>>` here
+   |            the method is available for `std::sync::Arc<std::rc::Rc<&mut std::boxed::Box<&char>>>` here
+   |            the method is available for `std::rc::Rc<std::rc::Rc<&mut std::boxed::Box<&char>>>` here
+...
 LL |     std::rc::Rc::new(&mut Box::new(&'a')).method();
    |                                           ^^^^^^
    |
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-method.rs b/src/test/ui/self/point-at-arbitrary-self-type-method.rs
new file mode 100644
index 0000000000000..0f7deeacad292
--- /dev/null
+++ b/src/test/ui/self/point-at-arbitrary-self-type-method.rs
@@ -0,0 +1,9 @@
+struct A;
+
+impl A {
+    fn foo(self: Box<Self>) {}
+}
+
+fn main() {
+    A.foo(); //~ ERROR E0599
+}
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-method.stderr b/src/test/ui/self/point-at-arbitrary-self-type-method.stderr
new file mode 100644
index 0000000000000..06dad7caa6735
--- /dev/null
+++ b/src/test/ui/self/point-at-arbitrary-self-type-method.stderr
@@ -0,0 +1,15 @@
+error[E0599]: no method named `foo` found for type `A` in the current scope
+  --> $DIR/point-at-arbitrary-self-type-method.rs:8:7
+   |
+LL | struct A;
+   | --------- method `foo` not found for this
+...
+LL |     fn foo(self: Box<Self>) {}
+   |        --- the method is available for `std::boxed::Box<A>` here
+...
+LL |     A.foo();
+   |       ^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-trait-method.rs b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.rs
new file mode 100644
index 0000000000000..53d992771186f
--- /dev/null
+++ b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.rs
@@ -0,0 +1,10 @@
+trait B { fn foo(self: Box<Self>); }
+struct A;
+
+impl B for A {
+    fn foo(self: Box<Self>) {}
+}
+
+fn main() {
+    A.foo() //~ ERROR E0599
+}
diff --git a/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr
new file mode 100644
index 0000000000000..90cd3b8074580
--- /dev/null
+++ b/src/test/ui/self/point-at-arbitrary-self-type-trait-method.stderr
@@ -0,0 +1,18 @@
+error[E0599]: no method named `foo` found for type `A` in the current scope
+  --> $DIR/point-at-arbitrary-self-type-trait-method.rs:9:7
+   |
+LL | trait B { fn foo(self: Box<Self>); }
+   |              --- the method is available for `std::boxed::Box<A>` here
+LL | struct A;
+   | --------- method `foo` not found for this
+...
+LL |     A.foo()
+   |       ^^^
+   |
+   = help: items from traits can only be used if the trait is implemented and in scope
+   = note: the following trait defines an item `foo`, perhaps you need to implement it:
+           candidate #1: `B`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/src/test/ui/traits/trait-item-privacy.stderr b/src/test/ui/traits/trait-item-privacy.stderr
index de699a69fa8bc..ce2919c8e7741 100644
--- a/src/test/ui/traits/trait-item-privacy.stderr
+++ b/src/test/ui/traits/trait-item-privacy.stderr
@@ -17,6 +17,13 @@ error[E0599]: no method named `b` found for type `S` in the current scope
 LL | struct S;
    | --------- method `b` not found for this
 ...
+LL |         fn b(&self) { }
+   |            -
+   |            |
+   |            the method is available for `std::boxed::Box<S>` here
+   |            the method is available for `std::sync::Arc<S>` here
+   |            the method is available for `std::rc::Rc<S>` here
+...
 LL |     S.b();
    |       ^
    |

From 84ccbe2076cf37bc13c32a89ccc57a57281b8708 Mon Sep 17 00:00:00 2001
From: Philipp Hansch <dev@phansch.net>
Date: Sun, 1 Sep 2019 12:15:33 +0200
Subject: [PATCH 05/33] librustc_errors: Extract sugg/subst handling into
 method

An initial refactoring before working on #61809.

This moves the whole block into a method so that it can be reused in the
annotate-snippet output. It's already used in the new emitter, but
there's no UI tests with suggestions included in this PR.

A first look at some UI tests with suggestions showed that there's some
more work to do in [annotate-snippet-rs][annotate-snippet-rs] before the
new output is closer to the current one.
---
 .../annotate_snippet_emitter_writer.rs        |  4 +-
 src/librustc_errors/emitter.rs                | 40 ++++++++++++++-----
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/src/librustc_errors/annotate_snippet_emitter_writer.rs b/src/librustc_errors/annotate_snippet_emitter_writer.rs
index 255af3122e70c..3bed5d81dc514 100644
--- a/src/librustc_errors/annotate_snippet_emitter_writer.rs
+++ b/src/librustc_errors/annotate_snippet_emitter_writer.rs
@@ -30,10 +30,8 @@ pub struct AnnotateSnippetEmitterWriter {
 impl Emitter for AnnotateSnippetEmitterWriter {
     /// The entry point for the diagnostics generation
     fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
-        let primary_span = db.span.clone();
         let children = db.children.clone();
-        // FIXME(#59346): Collect suggestions (see emitter.rs)
-        let suggestions: &[_] = &[];
+        let (primary_span, suggestions) = self.primary_span_formatted(&db);
 
         // FIXME(#59346): Add `fix_multispans_in_std_macros` function from emitter.rs
 
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 77d373e7a8ca8..0a9c927ef40a1 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -191,16 +191,25 @@ pub trait Emitter {
     fn should_show_explain(&self) -> bool {
         true
     }
-}
 
-impl Emitter for EmitterWriter {
-    fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
+    /// Formats the substitutions of the primary_span
+    ///
+    /// The are a lot of conditions to this method, but in short:
+    ///
+    /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
+    ///   we format the `help` suggestion depending on the content of the
+    ///   substitutions. In that case, we return the modified span only.
+    ///
+    /// * If the current `Diagnostic` has multiple suggestions,
+    ///   we return the original `primary_span` and the original suggestions.
+    fn primary_span_formatted<'a>(
+        &mut self,
+        db: &'a DiagnosticBuilder<'_>
+    ) -> (MultiSpan, &'a [CodeSuggestion]) {
         let mut primary_span = db.span.clone();
-        let mut children = db.children.clone();
-        let mut suggestions: &[_] = &[];
-
         if let Some((sugg, rest)) = db.suggestions.split_first() {
             if rest.is_empty() &&
+               // ^ if there is only one suggestion
                // don't display multi-suggestions as labels
                sugg.substitutions.len() == 1 &&
                // don't display multipart suggestions as labels
@@ -216,21 +225,34 @@ impl Emitter for EmitterWriter {
             {
                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
-                    // This substitution is only removal or we explicitly don't want to show the
-                    // code inline, don't show it
+                    // This substitution is only removal OR we explicitly don't want to show the
+                    // code inline (`hide_inline`). Therefore, we don't show the substitution.
                     format!("help: {}", sugg.msg)
                 } else {
+                    // Show the default suggestion text with the substitution
                     format!("help: {}: `{}`", sugg.msg, substitution)
                 };
                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
+
+                // We return only the modified primary_span
+                (primary_span, &[])
             } else {
                 // if there are multiple suggestions, print them all in full
                 // to be consistent. We could try to figure out if we can
                 // make one (or the first one) inline, but that would give
                 // undue importance to a semi-random suggestion
-                suggestions = &db.suggestions;
+                (primary_span, &db.suggestions)
             }
+        } else {
+            (primary_span, &db.suggestions)
         }
+    }
+}
+
+impl Emitter for EmitterWriter {
+    fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
+        let mut children = db.children.clone();
+        let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
 
         self.fix_multispans_in_std_macros(&mut primary_span,
                                           &mut children,

From 35c9e5f1229d8b634ebd98c49e35c74e237e17f7 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Sun, 1 Sep 2019 22:05:50 +0900
Subject: [PATCH 06/33] Fix const_err with `-(-0.0)`

---
 src/librustc_mir/transform/const_prop.rs | 14 +-------------
 src/test/ui/consts/const-err2.rs         |  1 -
 src/test/ui/consts/const-err2.stderr     | 20 +++++++-------------
 src/test/ui/consts/issue-64059.rs        |  5 +++++
 4 files changed, 13 insertions(+), 27 deletions(-)
 create mode 100644 src/test/ui/consts/issue-64059.rs

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index f261fdc268b5b..00118c05c9451 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -6,7 +6,7 @@ use std::cell::Cell;
 use rustc::hir::def::DefKind;
 use rustc::mir::{
     AggregateKind, Constant, Location, Place, PlaceBase, Body, Operand, Rvalue,
-    Local, NullOp, UnOp, StatementKind, Statement, LocalKind, Static, StaticKind,
+    Local, NullOp, StatementKind, Statement, LocalKind, Static, StaticKind,
     TerminatorKind, Terminator,  ClearCrossCrate, SourceInfo, BinOp, ProjectionElem,
     SourceScope, SourceScopeLocalData, LocalDecl,
 };
@@ -407,18 +407,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 let arg = self.eval_operand(arg, source_info)?;
                 let val = self.use_ecx(source_info, |this| {
                     let prim = this.ecx.read_immediate(arg)?;
-                    match op {
-                        UnOp::Neg => {
-                            // Need to do overflow check here: For actual CTFE, MIR
-                            // generation emits code that does this before calling the op.
-                            if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
-                                throw_panic!(OverflowNeg)
-                            }
-                        }
-                        UnOp::Not => {
-                            // Cannot overflow
-                        }
-                    }
                     // Now run the actual operation.
                     this.ecx.unary_op(op, prim)
                 })?;
diff --git a/src/test/ui/consts/const-err2.rs b/src/test/ui/consts/const-err2.rs
index a5f685a159b39..5aab1972a9bd5 100644
--- a/src/test/ui/consts/const-err2.rs
+++ b/src/test/ui/consts/const-err2.rs
@@ -13,7 +13,6 @@ fn black_box<T>(_: T) {
 
 fn main() {
     let a = -std::i8::MIN;
-    //~^ ERROR const_err
     let b = 200u8 + 200u8 + 200u8;
     //~^ ERROR const_err
     let c = 200u8 * 4;
diff --git a/src/test/ui/consts/const-err2.stderr b/src/test/ui/consts/const-err2.stderr
index 659c3afc618a9..63d037764a13d 100644
--- a/src/test/ui/consts/const-err2.stderr
+++ b/src/test/ui/consts/const-err2.stderr
@@ -1,8 +1,8 @@
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:15:13
+  --> $DIR/const-err2.rs:16:13
    |
-LL |     let a = -std::i8::MIN;
-   |             ^^^^^^^^^^^^^ attempt to negate with overflow
+LL |     let b = 200u8 + 200u8 + 200u8;
+   |             ^^^^^^^^^^^^^ attempt to add with overflow
    |
 note: lint level defined here
   --> $DIR/const-err2.rs:8:9
@@ -11,28 +11,22 @@ LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:17:13
-   |
-LL |     let b = 200u8 + 200u8 + 200u8;
-   |             ^^^^^^^^^^^^^ attempt to add with overflow
-
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:19:13
+  --> $DIR/const-err2.rs:18:13
    |
 LL |     let c = 200u8 * 4;
    |             ^^^^^^^^^ attempt to multiply with overflow
 
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:21:13
+  --> $DIR/const-err2.rs:20:13
    |
 LL |     let d = 42u8 - (42u8 + 1);
    |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
 
 error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:23:14
+  --> $DIR/const-err2.rs:22:14
    |
 LL |     let _e = [5u8][1];
    |              ^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/consts/issue-64059.rs b/src/test/ui/consts/issue-64059.rs
new file mode 100644
index 0000000000000..c4c895fef66cf
--- /dev/null
+++ b/src/test/ui/consts/issue-64059.rs
@@ -0,0 +1,5 @@
+// run-pass
+
+fn main() {
+    let _ = -(-0.0);
+}

From 3a6aadaa8c915c3dea42c0b1fb6d96f227166148 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Mon, 2 Sep 2019 01:05:38 +0900
Subject: [PATCH 07/33] Add `opt-level` check

---
 src/librustc_mir/transform/const_prop.rs      |  16 ++-
 src/test/ui/consts/const-err2.rs              |   3 -
 src/test/ui/consts/const-err2.stderr          |  28 +---
 .../ui/consts/const-eval/promoted_errors.rs   |   1 -
 .../consts/const-eval/promoted_errors.stderr  |  30 ++---
 ...t-method-self-inherit-builtin-trait.stderr |   6 +
 src/test/ui/issues/issue-8460-const.rs        |  10 --
 src/test/ui/issues/issue-8460-const.stderr    | 120 +++++-------------
 8 files changed, 67 insertions(+), 147 deletions(-)
 create mode 100644 src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 00118c05c9451..37e14004ce841 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -6,7 +6,7 @@ use std::cell::Cell;
 use rustc::hir::def::DefKind;
 use rustc::mir::{
     AggregateKind, Constant, Location, Place, PlaceBase, Body, Operand, Rvalue,
-    Local, NullOp, StatementKind, Statement, LocalKind, Static, StaticKind,
+    Local, NullOp, UnOp, StatementKind, Statement, LocalKind, Static, StaticKind,
     TerminatorKind, Terminator,  ClearCrossCrate, SourceInfo, BinOp, ProjectionElem,
     SourceScope, SourceScopeLocalData, LocalDecl,
 };
@@ -405,8 +405,20 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 }
 
                 let arg = self.eval_operand(arg, source_info)?;
+                let is_release_mode = self.tcx.sess.opts.debugging_opts.mir_opt_level >= 2;
                 let val = self.use_ecx(source_info, |this| {
                     let prim = this.ecx.read_immediate(arg)?;
+                    match op {
+                        UnOp::Neg => {
+                            if is_release_mode
+                            && prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
+                                throw_panic!(OverflowNeg)
+                            }
+                        }
+                        UnOp::Not => {
+                            // Cannot overflow
+                        }
+                    }
                     // Now run the actual operation.
                     this.ecx.unary_op(op, prim)
                 })?;
@@ -473,7 +485,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         Scalar::from_bool(overflow).into(),
                     )
                 } else {
-                    if overflow {
+                    if self.tcx.sess.opts.debugging_opts.mir_opt_level >= 2 && overflow {
                         let err = err_panic!(Overflow(op)).into();
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;
diff --git a/src/test/ui/consts/const-err2.rs b/src/test/ui/consts/const-err2.rs
index 5aab1972a9bd5..6da6addf60a1c 100644
--- a/src/test/ui/consts/const-err2.rs
+++ b/src/test/ui/consts/const-err2.rs
@@ -14,11 +14,8 @@ fn black_box<T>(_: T) {
 fn main() {
     let a = -std::i8::MIN;
     let b = 200u8 + 200u8 + 200u8;
-    //~^ ERROR const_err
     let c = 200u8 * 4;
-    //~^ ERROR const_err
     let d = 42u8 - (42u8 + 1);
-    //~^ ERROR const_err
     let _e = [5u8][1];
     //~^ ERROR const_err
     black_box(a);
diff --git a/src/test/ui/consts/const-err2.stderr b/src/test/ui/consts/const-err2.stderr
index 63d037764a13d..30855fd215ff3 100644
--- a/src/test/ui/consts/const-err2.stderr
+++ b/src/test/ui/consts/const-err2.stderr
@@ -1,8 +1,8 @@
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:16:13
+error: index out of bounds: the len is 1 but the index is 1
+  --> $DIR/const-err2.rs:19:14
    |
-LL |     let b = 200u8 + 200u8 + 200u8;
-   |             ^^^^^^^^^^^^^ attempt to add with overflow
+LL |     let _e = [5u8][1];
+   |              ^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/const-err2.rs:8:9
@@ -10,23 +10,5 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:18:13
-   |
-LL |     let c = 200u8 * 4;
-   |             ^^^^^^^^^ attempt to multiply with overflow
-
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:20:13
-   |
-LL |     let d = 42u8 - (42u8 + 1);
-   |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
-
-error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:22:14
-   |
-LL |     let _e = [5u8][1];
-   |              ^^^^^^^^
-
-error: aborting due to 4 previous errors
+error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-eval/promoted_errors.rs b/src/test/ui/consts/const-eval/promoted_errors.rs
index cd989731452b3..a9a7a66fe614f 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.rs
+++ b/src/test/ui/consts/const-eval/promoted_errors.rs
@@ -5,7 +5,6 @@
 fn main() {
     println!("{}", 0u32 - 1);
     let _x = 0u32 - 1;
-    //~^ ERROR this expression will panic at runtime [const_err]
     println!("{}", 1/(1-1));
     //~^ ERROR attempt to divide by zero [const_err]
     //~| ERROR reaching this expression at runtime will panic or abort [const_err]
diff --git a/src/test/ui/consts/const-eval/promoted_errors.stderr b/src/test/ui/consts/const-eval/promoted_errors.stderr
index 40d5c73e86679..3940fa13d7892 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.stderr
@@ -1,8 +1,8 @@
-error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:7:14
+error: attempt to divide by zero
+  --> $DIR/promoted_errors.rs:8:20
    |
-LL |     let _x = 0u32 - 1;
-   |              ^^^^^^^^ attempt to subtract with overflow
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^
    |
 note: lint level defined here
   --> $DIR/promoted_errors.rs:3:9
@@ -10,53 +10,47 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:9:20
-   |
-LL |     println!("{}", 1/(1-1));
-   |                    ^^^^^^^
-
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:9:20
+  --> $DIR/promoted_errors.rs:8:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:12:14
+  --> $DIR/promoted_errors.rs:11:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:12:14
+  --> $DIR/promoted_errors.rs:11:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:15:20
+  --> $DIR/promoted_errors.rs:14:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:15:20
+  --> $DIR/promoted_errors.rs:14:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:18:14
+  --> $DIR/promoted_errors.rs:17:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:18:14
+  --> $DIR/promoted_errors.rs:17:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
-error: aborting due to 9 previous errors
+error: aborting due to 8 previous errors
 
diff --git a/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr b/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr
new file mode 100644
index 0000000000000..5160c9e72a9c4
--- /dev/null
+++ b/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr
@@ -0,0 +1,6 @@
+error: failed to remove $TEST_BUILD_DIR/issues/issue-8171-default-method-self-inherit-builtin-trait/issue-8171-default-method-self-inherit-builtin-trait.issue_8171_default_method_self_inherit_builtin_trait.7rcbfp3g-cgu.0.rcgu.o: 指定されたパスが見つかりません。 (os error 3)
+
+error: failed to remove $TEST_BUILD_DIR/issues/issue-8171-default-method-self-inherit-builtin-trait/issue-8171-default-method-self-inherit-builtin-trait.issue_8171_default_method_self_inherit_builtin_trait.7rcbfp3g-cgu.1.rcgu.o: 指定されたパスが見つかりません。 (os error 3)
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/issues/issue-8460-const.rs b/src/test/ui/issues/issue-8460-const.rs
index 611d280f774c0..6a5b98fa9b190 100644
--- a/src/test/ui/issues/issue-8460-const.rs
+++ b/src/test/ui/issues/issue-8460-const.rs
@@ -6,19 +6,14 @@ use std::thread;
 fn main() {
     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
     //~^ ERROR attempt to divide by zero
     //~| ERROR this expression will panic at runtime
@@ -36,19 +31,14 @@ fn main() {
     //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with a divisor of zero
     //~| ERROR this expression will panic at runtime
diff --git a/src/test/ui/issues/issue-8460-const.stderr b/src/test/ui/issues/issue-8460-const.stderr
index 31b1da4f804ab..b9fbf0bdaa609 100644
--- a/src/test/ui/issues/issue-8460-const.stderr
+++ b/src/test/ui/issues/issue-8460-const.stderr
@@ -10,239 +10,179 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:7:36
-   |
-LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:10:36
+  --> $DIR/issue-8460-const.rs:9:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:10:36
-   |
-LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:13:36
+  --> $DIR/issue-8460-const.rs:11:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:13:36
-   |
-LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:16:36
+  --> $DIR/issue-8460-const.rs:13:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:16:36
-   |
-LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:19:36
+  --> $DIR/issue-8460-const.rs:15:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:19:36
-   |
-LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:17:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:17:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:20:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:20:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:23:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:23:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:26:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:26:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:29:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:29:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:37:36
+  --> $DIR/issue-8460-const.rs:32:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:37:36
-   |
-LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:40:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:40:36
-   |
-LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:43:36
+  --> $DIR/issue-8460-const.rs:36:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:43:36
-   |
-LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:46:36
+  --> $DIR/issue-8460-const.rs:38:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:46:36
-   |
-LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:49:36
+  --> $DIR/issue-8460-const.rs:40:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:49:36
-   |
-LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:52:36
+  --> $DIR/issue-8460-const.rs:42:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:52:36
+  --> $DIR/issue-8460-const.rs:42:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:55:36
+  --> $DIR/issue-8460-const.rs:45:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:55:36
+  --> $DIR/issue-8460-const.rs:45:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:58:36
+  --> $DIR/issue-8460-const.rs:48:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:58:36
+  --> $DIR/issue-8460-const.rs:48:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:61:36
+  --> $DIR/issue-8460-const.rs:51:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:61:36
+  --> $DIR/issue-8460-const.rs:51:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:64:36
+  --> $DIR/issue-8460-const.rs:54:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:64:36
+  --> $DIR/issue-8460-const.rs:54:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: aborting due to 40 previous errors
+error: aborting due to 30 previous errors
 

From ab12dfeb164fb06d19ce24acd8268eebfd6440fa Mon Sep 17 00:00:00 2001
From: Guanqun Lu <guanqun.lu@gmail.com>
Date: Mon, 2 Sep 2019 00:38:05 +0800
Subject: [PATCH 08/33] following the same style

---
 src/tools/compiletest/src/main.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index bde49ff391c8c..467b7771c152e 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -335,7 +335,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         runtool: matches.opt_str("runtool"),
         host_rustcflags: matches.opt_str("host-rustcflags"),
         target_rustcflags: matches.opt_str("target-rustcflags"),
-        target: target,
+        target,
         host: opt_str2(matches.opt_str("host")),
         cdb,
         gdb,
@@ -345,7 +345,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         lldb_native_rust,
         llvm_version: matches.opt_str("llvm-version"),
         system_llvm: matches.opt_present("system-llvm"),
-        android_cross_path: android_cross_path,
+        android_cross_path,
         adb_path: opt_str2(matches.opt_str("adb-path")),
         adb_test_dir: opt_str2(matches.opt_str("adb-test-dir")),
         adb_device_status: opt_str2(matches.opt_str("target")).contains("android")

From 4a0872b37efbd982aed7e29f166e4ccb095f5779 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Mon, 2 Sep 2019 02:18:16 +0900
Subject: [PATCH 09/33] Add `overflow_check` check

---
 src/librustc_mir/transform/const_prop.rs                  | 8 ++++++--
 ...-8171-default-method-self-inherit-builtin-trait.stderr | 6 ------
 2 files changed, 6 insertions(+), 8 deletions(-)
 delete mode 100644 src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 37e14004ce841..b43323687cda3 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -405,11 +405,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 }
 
                 let arg = self.eval_operand(arg, source_info)?;
-                let is_release_mode = self.tcx.sess.opts.debugging_opts.mir_opt_level >= 2;
+                let is_release_mode = self.tcx.sess.overflow_checks();
                 let val = self.use_ecx(source_info, |this| {
                     let prim = this.ecx.read_immediate(arg)?;
                     match op {
                         UnOp::Neg => {
+                            // We don't have to check overflow here when we already
+                            // check it in release mode.
                             if is_release_mode
                             && prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
                                 throw_panic!(OverflowNeg)
@@ -485,7 +487,9 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         Scalar::from_bool(overflow).into(),
                     )
                 } else {
-                    if self.tcx.sess.opts.debugging_opts.mir_opt_level >= 2 && overflow {
+                    // We don't have to check overflow here when we already
+                    // check it in release mode.
+                    if self.tcx.sess.overflow_checks() && overflow {
                         let err = err_panic!(Overflow(op)).into();
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;
diff --git a/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr b/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr
deleted file mode 100644
index 5160c9e72a9c4..0000000000000
--- a/src/test/ui/issues/issue-8171-default-method-self-inherit-builtin-trait.stderr
+++ /dev/null
@@ -1,6 +0,0 @@
-error: failed to remove $TEST_BUILD_DIR/issues/issue-8171-default-method-self-inherit-builtin-trait/issue-8171-default-method-self-inherit-builtin-trait.issue_8171_default_method_self_inherit_builtin_trait.7rcbfp3g-cgu.0.rcgu.o: 指定されたパスが見つかりません。 (os error 3)
-
-error: failed to remove $TEST_BUILD_DIR/issues/issue-8171-default-method-self-inherit-builtin-trait/issue-8171-default-method-self-inherit-builtin-trait.issue_8171_default_method_self_inherit_builtin_trait.7rcbfp3g-cgu.1.rcgu.o: 指定されたパスが見つかりません。 (os error 3)
-
-error: aborting due to 2 previous errors
-

From f53c2179ba2ae35bd241a28027fb703aec89139b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 1 Sep 2019 10:49:07 -0700
Subject: [PATCH 10/33] review comments

---
 src/librustc_typeck/check/_match.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index 63d059bdf2a80..7427ae9ce8de3 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -117,14 +117,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 &arms[0].body,
                 &mut coercion,
             ) {
-                    tcx.types.err
+                tcx.types.err
             } else {
                 // Only call this if this is not an `if` expr with an expected type and no `else`
                 // clause to avoid duplicated type errors. (#60254)
-                let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
-                all_arms_diverge &= self.diverges.get();
-                arm_ty
+                self.check_expr_with_expectation(&arm.body, expected)
             };
+            all_arms_diverge &= self.diverges.get();
             if source_if {
                 let then_expr = &arms[0].body;
                 match (i, if_no_else) {
@@ -188,6 +187,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// Handle the fallback arm of a desugared if(-let) like a missing else.
+    ///
+    /// Returns `true` if there was an error forcing the coercion to the `()` type.
     fn if_fallback_coercion(
         &self,
         span: Span,

From 8e9825aeb9bce905ed230733bf2a5b4b07f25eb9 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Mon, 2 Sep 2019 03:06:11 +0900
Subject: [PATCH 11/33] Fix overflow_check

---
 src/librustc_mir/transform/const_prop.rs      |  14 +-
 src/test/ui/consts/const-err2.rs              |   4 +
 src/test/ui/consts/const-err2.stderr          |  34 ++++-
 .../ui/consts/const-eval/promoted_errors.rs   |   1 +
 .../consts/const-eval/promoted_errors.stderr  |  30 +++--
 src/test/ui/consts/issue-64059.rs             |   3 +-
 src/test/ui/consts/issue-64059.stderr         |  10 ++
 src/test/ui/issues/issue-8460-const.rs        |  10 ++
 src/test/ui/issues/issue-8460-const.stderr    | 120 +++++++++++++-----
 9 files changed, 170 insertions(+), 56 deletions(-)
 create mode 100644 src/test/ui/consts/issue-64059.stderr

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index b43323687cda3..091e68cd0669c 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -405,14 +405,14 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 }
 
                 let arg = self.eval_operand(arg, source_info)?;
-                let is_release_mode = self.tcx.sess.overflow_checks();
+                let oflo_check = self.tcx.sess.overflow_checks();
                 let val = self.use_ecx(source_info, |this| {
                     let prim = this.ecx.read_immediate(arg)?;
                     match op {
                         UnOp::Neg => {
-                            // We don't have to check overflow here when we already
-                            // check it in release mode.
-                            if is_release_mode
+                            // We check overflow in debug mode already
+                            // so should only check in release mode.
+                            if !oflo_check
                             && prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
                                 throw_panic!(OverflowNeg)
                             }
@@ -487,9 +487,9 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         Scalar::from_bool(overflow).into(),
                     )
                 } else {
-                    // We don't have to check overflow here when we already
-                    // check it in release mode.
-                    if self.tcx.sess.overflow_checks() && overflow {
+                    // We check overflow in debug mode already
+                    // so should only check in release mode.
+                    if !self.tcx.sess.overflow_checks() && overflow {
                         let err = err_panic!(Overflow(op)).into();
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;
diff --git a/src/test/ui/consts/const-err2.rs b/src/test/ui/consts/const-err2.rs
index 6da6addf60a1c..a5f685a159b39 100644
--- a/src/test/ui/consts/const-err2.rs
+++ b/src/test/ui/consts/const-err2.rs
@@ -13,9 +13,13 @@ fn black_box<T>(_: T) {
 
 fn main() {
     let a = -std::i8::MIN;
+    //~^ ERROR const_err
     let b = 200u8 + 200u8 + 200u8;
+    //~^ ERROR const_err
     let c = 200u8 * 4;
+    //~^ ERROR const_err
     let d = 42u8 - (42u8 + 1);
+    //~^ ERROR const_err
     let _e = [5u8][1];
     //~^ ERROR const_err
     black_box(a);
diff --git a/src/test/ui/consts/const-err2.stderr b/src/test/ui/consts/const-err2.stderr
index 30855fd215ff3..659c3afc618a9 100644
--- a/src/test/ui/consts/const-err2.stderr
+++ b/src/test/ui/consts/const-err2.stderr
@@ -1,8 +1,8 @@
-error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:19:14
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:15:13
    |
-LL |     let _e = [5u8][1];
-   |              ^^^^^^^^
+LL |     let a = -std::i8::MIN;
+   |             ^^^^^^^^^^^^^ attempt to negate with overflow
    |
 note: lint level defined here
   --> $DIR/const-err2.rs:8:9
@@ -10,5 +10,29 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: aborting due to previous error
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:17:13
+   |
+LL |     let b = 200u8 + 200u8 + 200u8;
+   |             ^^^^^^^^^^^^^ attempt to add with overflow
+
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:19:13
+   |
+LL |     let c = 200u8 * 4;
+   |             ^^^^^^^^^ attempt to multiply with overflow
+
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:21:13
+   |
+LL |     let d = 42u8 - (42u8 + 1);
+   |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
+
+error: index out of bounds: the len is 1 but the index is 1
+  --> $DIR/const-err2.rs:23:14
+   |
+LL |     let _e = [5u8][1];
+   |              ^^^^^^^^
+
+error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/consts/const-eval/promoted_errors.rs b/src/test/ui/consts/const-eval/promoted_errors.rs
index a9a7a66fe614f..cd989731452b3 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.rs
+++ b/src/test/ui/consts/const-eval/promoted_errors.rs
@@ -5,6 +5,7 @@
 fn main() {
     println!("{}", 0u32 - 1);
     let _x = 0u32 - 1;
+    //~^ ERROR this expression will panic at runtime [const_err]
     println!("{}", 1/(1-1));
     //~^ ERROR attempt to divide by zero [const_err]
     //~| ERROR reaching this expression at runtime will panic or abort [const_err]
diff --git a/src/test/ui/consts/const-eval/promoted_errors.stderr b/src/test/ui/consts/const-eval/promoted_errors.stderr
index 3940fa13d7892..40d5c73e86679 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.stderr
@@ -1,8 +1,8 @@
-error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:8:20
+error: this expression will panic at runtime
+  --> $DIR/promoted_errors.rs:7:14
    |
-LL |     println!("{}", 1/(1-1));
-   |                    ^^^^^^^
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^ attempt to subtract with overflow
    |
 note: lint level defined here
   --> $DIR/promoted_errors.rs:3:9
@@ -10,47 +10,53 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
+error: attempt to divide by zero
+  --> $DIR/promoted_errors.rs:9:20
+   |
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^
+
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:8:20
+  --> $DIR/promoted_errors.rs:9:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:11:14
+  --> $DIR/promoted_errors.rs:12:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:11:14
+  --> $DIR/promoted_errors.rs:12:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:14:20
+  --> $DIR/promoted_errors.rs:15:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:14:20
+  --> $DIR/promoted_errors.rs:15:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:17:14
+  --> $DIR/promoted_errors.rs:18:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:17:14
+  --> $DIR/promoted_errors.rs:18:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
-error: aborting due to 8 previous errors
+error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/consts/issue-64059.rs b/src/test/ui/consts/issue-64059.rs
index c4c895fef66cf..30b8744cb7fa7 100644
--- a/src/test/ui/consts/issue-64059.rs
+++ b/src/test/ui/consts/issue-64059.rs
@@ -1,5 +1,4 @@
-// run-pass
-
 fn main() {
     let _ = -(-0.0);
+    //~^ ERROR: this expression will panic at runtime
 }
diff --git a/src/test/ui/consts/issue-64059.stderr b/src/test/ui/consts/issue-64059.stderr
new file mode 100644
index 0000000000000..6f27653421bd6
--- /dev/null
+++ b/src/test/ui/consts/issue-64059.stderr
@@ -0,0 +1,10 @@
+error: this expression will panic at runtime
+  --> $DIR/issue-64059.rs:2:13
+   |
+LL |     let _ = -(-0.0);
+   |             ^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(const_err)]` on by default
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/issues/issue-8460-const.rs b/src/test/ui/issues/issue-8460-const.rs
index 6a5b98fa9b190..611d280f774c0 100644
--- a/src/test/ui/issues/issue-8460-const.rs
+++ b/src/test/ui/issues/issue-8460-const.rs
@@ -6,14 +6,19 @@ use std::thread;
 fn main() {
     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
     //~^ ERROR attempt to divide by zero
     //~| ERROR this expression will panic at runtime
@@ -31,14 +36,19 @@ fn main() {
     //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with a divisor of zero
     //~| ERROR this expression will panic at runtime
diff --git a/src/test/ui/issues/issue-8460-const.stderr b/src/test/ui/issues/issue-8460-const.stderr
index b9fbf0bdaa609..31b1da4f804ab 100644
--- a/src/test/ui/issues/issue-8460-const.stderr
+++ b/src/test/ui/issues/issue-8460-const.stderr
@@ -10,179 +10,239 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:7:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:9:36
+  --> $DIR/issue-8460-const.rs:10:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:10:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:11:36
+  --> $DIR/issue-8460-const.rs:13:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: attempt to divide with overflow
+error: this expression will panic at runtime
   --> $DIR/issue-8460-const.rs:13:36
    |
+LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const.rs:16:36
+   |
 LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:16:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:15:36
+  --> $DIR/issue-8460-const.rs:19:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:19:36
+   |
+LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:17:36
+  --> $DIR/issue-8460-const.rs:22:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:17:36
+  --> $DIR/issue-8460-const.rs:22:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:20:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:20:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:23:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:23:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:26:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:26:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:29:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:29:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:32:36
+  --> $DIR/issue-8460-const.rs:37:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:37:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:40:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:40:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:36:36
+  --> $DIR/issue-8460-const.rs:43:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:43:36
+   |
+LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:38:36
+  --> $DIR/issue-8460-const.rs:46:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:46:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:40:36
+  --> $DIR/issue-8460-const.rs:49:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:49:36
+   |
+LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:42:36
+  --> $DIR/issue-8460-const.rs:52:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:42:36
+  --> $DIR/issue-8460-const.rs:52:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:45:36
+  --> $DIR/issue-8460-const.rs:55:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:45:36
+  --> $DIR/issue-8460-const.rs:55:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:48:36
+  --> $DIR/issue-8460-const.rs:58:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:48:36
+  --> $DIR/issue-8460-const.rs:58:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:51:36
+  --> $DIR/issue-8460-const.rs:61:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:51:36
+  --> $DIR/issue-8460-const.rs:61:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:54:36
+  --> $DIR/issue-8460-const.rs:64:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:54:36
+  --> $DIR/issue-8460-const.rs:64:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: aborting due to 30 previous errors
+error: aborting due to 40 previous errors
 

From 141f5a7558289acb6c7aaf9c6500eb9f6dbeec1a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 1 Sep 2019 11:20:33 -0700
Subject: [PATCH 12/33] review comments

---
 src/librustc/ty/context.rs        | 16 +-----
 src/librustc_typeck/check/expr.rs | 94 ++++++++++++++++++-------------
 2 files changed, 57 insertions(+), 53 deletions(-)

diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index f355e231914d2..17c9e520bcea2 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -2403,20 +2403,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline]
-    pub fn mk_pin(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(lang_items::PinTypeLangItem, None);
-        self.mk_generic_adt(def_id, ty)
-    }
-
-    #[inline]
-    pub fn mk_rc(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(lang_items::Rc, None);
-        self.mk_generic_adt(def_id, ty)
-    }
-
-    #[inline]
-    pub fn mk_arc(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(lang_items::Arc, None);
+    pub fn mk_lang_item(self, ty: Ty<'tcx>, item: lang_items::LangItem)  -> Ty<'tcx> {
+        let def_id = self.require_lang_item(item, None);
         self.mk_generic_adt(def_id, ty)
     }
 
diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
index efff8bcdacbcf..fbaa9904d8303 100644
--- a/src/librustc_typeck/check/expr.rs
+++ b/src/librustc_typeck/check/expr.rs
@@ -12,7 +12,7 @@ use crate::check::fatally_break_rust;
 use crate::check::report_unexpected_variant_res;
 use crate::check::Needs;
 use crate::check::TupleArgumentsFlag::DontTupleArguments;
-use crate::check::method::{probe, SelfSource};
+use crate::check::method::{probe, SelfSource, MethodError};
 use crate::util::common::ErrorReported;
 use crate::util::nodemap::FxHashMap;
 use crate::astconv::AstConv as _;
@@ -29,6 +29,7 @@ use rustc::hir::def::{CtorKind, Res, DefKind};
 use rustc::hir::ptr::P;
 use rustc::infer;
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc::middle::lang_items;
 use rustc::mir::interpret::GlobalId;
 use rustc::ty;
 use rustc::ty::adjustment::{
@@ -775,21 +776,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // no need to check for bot/err -- callee does that
         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
 
-        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
-            if let Ok(pick) = self.lookup_probe(
-                span,
-                segment.ident,
-                new_rcvr_t,
-                rcvr,
-                probe::ProbeScope::AllTraits,
-            ) {
-                err.span_label(
-                    pick.item.ident.span,
-                    &format!("the method is available for `{}` here", new_rcvr_t),
-                );
-            }
-        };
-
         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr) {
             Ok(method) => {
                 self.write_method_call(expr.hir_id, method);
@@ -797,29 +783,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             Err(error) => {
                 if segment.ident.name != kw::Invalid {
-                    if let Some(mut err) = self.report_method_error(
-                        span,
-                        rcvr_t,
-                        segment.ident,
-                        SelfSource::MethodCall(rcvr),
-                        error,
-                        Some(args),
-                    ) {
-                        if let ty::Adt(..) = rcvr_t.sty {
-                            // Try alternative arbitrary self types that could fulfill this call.
-                            // FIXME: probe for all types that *could* be arbitrary self-types, not
-                            // just this whitelist.
-                            let box_rcvr_t = self.tcx.mk_box(rcvr_t);
-                            try_alt_rcvr(&mut err, box_rcvr_t);
-                            let pin_rcvr_t = self.tcx.mk_pin(rcvr_t);
-                            try_alt_rcvr(&mut err, pin_rcvr_t);
-                            let arc_rcvr_t = self.tcx.mk_arc(rcvr_t);
-                            try_alt_rcvr(&mut err, arc_rcvr_t);
-                            let rc_rcvr_t = self.tcx.mk_rc(rcvr_t);
-                            try_alt_rcvr(&mut err, rc_rcvr_t);
-                        }
-                        err.emit();
-                    }
+                    self.report_extended_method_error(segment, span, args, rcvr_t, error);
                 }
                 Err(())
             }
@@ -836,6 +800,58 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
+    fn report_extended_method_error(
+        &self,
+        segment: &hir::PathSegment,
+        span: Span,
+        args: &'tcx [hir::Expr],
+        rcvr_t: Ty<'tcx>,
+        error: MethodError<'tcx>
+    ) {
+        let rcvr = &args[0];
+        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
+            if let Ok(pick) = self.lookup_probe(
+                span,
+                segment.ident,
+                new_rcvr_t,
+                rcvr,
+                probe::ProbeScope::AllTraits,
+            ) {
+                err.span_label(
+                    pick.item.ident.span,
+                    &format!("the method is available for `{}` here", new_rcvr_t),
+                );
+            }
+        };
+
+        if let Some(mut err) = self.report_method_error(
+            span,
+            rcvr_t,
+            segment.ident,
+            SelfSource::MethodCall(rcvr),
+            error,
+            Some(args),
+        ) {
+            if let ty::Adt(..) = rcvr_t.sty {
+                // Try alternative arbitrary self types that could fulfill this call.
+                // FIXME: probe for all types that *could* be arbitrary self-types, not
+                // just this whitelist.
+                let box_rcvr_t = self.tcx.mk_box(rcvr_t);
+                try_alt_rcvr(&mut err, box_rcvr_t);
+                let pin_rcvr_t = self.tcx.mk_lang_item(
+                    rcvr_t,
+                    lang_items::PinTypeLangItem,
+                );
+                try_alt_rcvr(&mut err, pin_rcvr_t);
+                let arc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Arc);
+                try_alt_rcvr(&mut err, arc_rcvr_t);
+                let rc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Rc);
+                try_alt_rcvr(&mut err, rc_rcvr_t);
+            }
+            err.emit();
+        }
+    }
+
     fn check_expr_cast(
         &self,
         e: &'tcx hir::Expr,

From 0cd9c1623fb5858990892fed2fbf7c06e7b25f22 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Mon, 2 Sep 2019 03:40:35 +0900
Subject: [PATCH 13/33] Fix condition and tests' flags

---
 src/librustc_mir/transform/const_prop.rs      |   1 +
 src/test/ui/consts/const-err2.rs              |   2 +
 src/test/ui/consts/const-err2.stderr          |  28 ++--
 .../ui/consts/const-eval/promoted_errors.rs   |   5 +-
 .../consts/const-eval/promoted_errors.stderr  |  32 +++--
 src/test/ui/consts/issue-64059.rs             |   4 +-
 src/test/ui/consts/issue-64059.stderr         |  10 --
 src/test/ui/issues/issue-8460-const.rs        |  12 +-
 src/test/ui/issues/issue-8460-const.stderr    | 122 +++++-------------
 9 files changed, 75 insertions(+), 141 deletions(-)
 delete mode 100644 src/test/ui/consts/issue-64059.stderr

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 091e68cd0669c..e4b186736e2a1 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -413,6 +413,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                             // We check overflow in debug mode already
                             // so should only check in release mode.
                             if !oflo_check
+                            && prim.layout.ty.is_signed()
                             && prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
                                 throw_panic!(OverflowNeg)
                             }
diff --git a/src/test/ui/consts/const-err2.rs b/src/test/ui/consts/const-err2.rs
index a5f685a159b39..cd6ac47bd92a8 100644
--- a/src/test/ui/consts/const-err2.rs
+++ b/src/test/ui/consts/const-err2.rs
@@ -5,6 +5,8 @@
 
 #![feature(rustc_attrs)]
 #![allow(exceeding_bitshifts)]
+// compile-flags: -C overflow-checks=on -O
+
 #![deny(const_err)]
 
 fn black_box<T>(_: T) {
diff --git a/src/test/ui/consts/const-err2.stderr b/src/test/ui/consts/const-err2.stderr
index 659c3afc618a9..ecfced7f0db8b 100644
--- a/src/test/ui/consts/const-err2.stderr
+++ b/src/test/ui/consts/const-err2.stderr
@@ -1,35 +1,35 @@
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:15:13
+error: attempt to negate with overflow
+  --> $DIR/const-err2.rs:17:13
    |
 LL |     let a = -std::i8::MIN;
-   |             ^^^^^^^^^^^^^ attempt to negate with overflow
+   |             ^^^^^^^^^^^^^
    |
 note: lint level defined here
-  --> $DIR/const-err2.rs:8:9
+  --> $DIR/const-err2.rs:10:9
    |
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:17:13
+error: attempt to add with overflow
+  --> $DIR/const-err2.rs:19:13
    |
 LL |     let b = 200u8 + 200u8 + 200u8;
-   |             ^^^^^^^^^^^^^ attempt to add with overflow
+   |             ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:19:13
+error: attempt to multiply with overflow
+  --> $DIR/const-err2.rs:21:13
    |
 LL |     let c = 200u8 * 4;
-   |             ^^^^^^^^^ attempt to multiply with overflow
+   |             ^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:21:13
+error: attempt to subtract with overflow
+  --> $DIR/const-err2.rs:23:13
    |
 LL |     let d = 42u8 - (42u8 + 1);
-   |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
+   |             ^^^^^^^^^^^^^^^^^
 
 error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:23:14
+  --> $DIR/const-err2.rs:25:14
    |
 LL |     let _e = [5u8][1];
    |              ^^^^^^^^
diff --git a/src/test/ui/consts/const-eval/promoted_errors.rs b/src/test/ui/consts/const-eval/promoted_errors.rs
index cd989731452b3..7adb394144bdd 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.rs
+++ b/src/test/ui/consts/const-eval/promoted_errors.rs
@@ -1,11 +1,12 @@
-// compile-flags: -O
+// compile-flags: -C overflow-checks=on -O
 
 #![deny(const_err)]
 
 fn main() {
     println!("{}", 0u32 - 1);
+    //~^ ERROR attempt to subtract with overflow
     let _x = 0u32 - 1;
-    //~^ ERROR this expression will panic at runtime [const_err]
+    //~^ ERROR attempt to subtract with overflow
     println!("{}", 1/(1-1));
     //~^ ERROR attempt to divide by zero [const_err]
     //~| ERROR reaching this expression at runtime will panic or abort [const_err]
diff --git a/src/test/ui/consts/const-eval/promoted_errors.stderr b/src/test/ui/consts/const-eval/promoted_errors.stderr
index 40d5c73e86679..fe63d0800dd7c 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.stderr
@@ -1,8 +1,8 @@
-error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:7:14
+error: attempt to subtract with overflow
+  --> $DIR/promoted_errors.rs:6:20
    |
-LL |     let _x = 0u32 - 1;
-   |              ^^^^^^^^ attempt to subtract with overflow
+LL |     println!("{}", 0u32 - 1);
+   |                    ^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/promoted_errors.rs:3:9
@@ -10,53 +10,59 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
+error: attempt to subtract with overflow
+  --> $DIR/promoted_errors.rs:8:14
+   |
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^
+
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:9:20
+  --> $DIR/promoted_errors.rs:10:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:9:20
+  --> $DIR/promoted_errors.rs:10:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:12:14
+  --> $DIR/promoted_errors.rs:13:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:12:14
+  --> $DIR/promoted_errors.rs:13:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:15:20
+  --> $DIR/promoted_errors.rs:16:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:15:20
+  --> $DIR/promoted_errors.rs:16:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:18:14
+  --> $DIR/promoted_errors.rs:19:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:18:14
+  --> $DIR/promoted_errors.rs:19:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
diff --git a/src/test/ui/consts/issue-64059.rs b/src/test/ui/consts/issue-64059.rs
index 30b8744cb7fa7..38911c3dcf692 100644
--- a/src/test/ui/consts/issue-64059.rs
+++ b/src/test/ui/consts/issue-64059.rs
@@ -1,4 +1,6 @@
+// compile-flags: -C overflow-checks=on -O
+// run-pass
+
 fn main() {
     let _ = -(-0.0);
-    //~^ ERROR: this expression will panic at runtime
 }
diff --git a/src/test/ui/consts/issue-64059.stderr b/src/test/ui/consts/issue-64059.stderr
deleted file mode 100644
index 6f27653421bd6..0000000000000
--- a/src/test/ui/consts/issue-64059.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: this expression will panic at runtime
-  --> $DIR/issue-64059.rs:2:13
-   |
-LL |     let _ = -(-0.0);
-   |             ^^^^^^^ attempt to negate with overflow
-   |
-   = note: `#[deny(const_err)]` on by default
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/issues/issue-8460-const.rs b/src/test/ui/issues/issue-8460-const.rs
index 611d280f774c0..c3f53e3298b2b 100644
--- a/src/test/ui/issues/issue-8460-const.rs
+++ b/src/test/ui/issues/issue-8460-const.rs
@@ -1,3 +1,5 @@
+// compile-flags: -C overflow-checks=on -O
+
 #![deny(const_err)]
 
 use std::{isize, i8, i16, i32, i64};
@@ -6,19 +8,14 @@ use std::thread;
 fn main() {
     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
     //~^ ERROR attempt to divide by zero
     //~| ERROR this expression will panic at runtime
@@ -36,19 +33,14 @@ fn main() {
     //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
-    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with a divisor of zero
     //~| ERROR this expression will panic at runtime
diff --git a/src/test/ui/issues/issue-8460-const.stderr b/src/test/ui/issues/issue-8460-const.stderr
index 31b1da4f804ab..914323227ddd2 100644
--- a/src/test/ui/issues/issue-8460-const.stderr
+++ b/src/test/ui/issues/issue-8460-const.stderr
@@ -1,248 +1,188 @@
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:7:36
+  --> $DIR/issue-8460-const.rs:9:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
    |
 note: lint level defined here
-  --> $DIR/issue-8460-const.rs:1:9
+  --> $DIR/issue-8460-const.rs:3:9
    |
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:7:36
-   |
-LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:10:36
+  --> $DIR/issue-8460-const.rs:11:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:10:36
-   |
-LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
   --> $DIR/issue-8460-const.rs:13:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:13:36
-   |
-LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:16:36
+  --> $DIR/issue-8460-const.rs:15:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:16:36
-   |
-LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:19:36
+  --> $DIR/issue-8460-const.rs:17:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:19:36
-   |
-LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
-
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:19:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:19:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:22:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:22:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:37:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:37:36
-   |
-LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:40:36
+  --> $DIR/issue-8460-const.rs:36:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:40:36
-   |
-LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:43:36
+  --> $DIR/issue-8460-const.rs:38:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:43:36
-   |
-LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:46:36
+  --> $DIR/issue-8460-const.rs:40:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:46:36
-   |
-LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:49:36
+  --> $DIR/issue-8460-const.rs:42:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:49:36
-   |
-LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
-   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
-
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:52:36
+  --> $DIR/issue-8460-const.rs:44:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:52:36
+  --> $DIR/issue-8460-const.rs:44:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:55:36
+  --> $DIR/issue-8460-const.rs:47:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:55:36
+  --> $DIR/issue-8460-const.rs:47:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:58:36
+  --> $DIR/issue-8460-const.rs:50:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:58:36
+  --> $DIR/issue-8460-const.rs:50:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:61:36
+  --> $DIR/issue-8460-const.rs:53:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:61:36
+  --> $DIR/issue-8460-const.rs:53:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:64:36
+  --> $DIR/issue-8460-const.rs:56:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:64:36
+  --> $DIR/issue-8460-const.rs:56:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: aborting due to 40 previous errors
+error: aborting due to 30 previous errors
 

From a937d8cdeb56ed72897ecf14469f89f18814554c Mon Sep 17 00:00:00 2001
From: Yuki Okushi <huyuumi.dev@gmail.com>
Date: Mon, 2 Sep 2019 05:01:39 +0900
Subject: [PATCH 14/33] Fix tests again

---
 src/test/ui/consts/const-err2.rs              |   3 +-
 src/test/ui/consts/const-err2.stderr          |  28 +--
 src/test/ui/consts/const-err3.rs              |  30 +++
 src/test/ui/consts/const-err3.stderr          |  38 ++++
 .../ui/consts/const-eval/promoted_errors.rs   |   5 +-
 .../consts/const-eval/promoted_errors.stderr  |  32 ++-
 .../ui/consts/const-eval/promoted_errors2.rs  |  22 ++
 .../consts/const-eval/promoted_errors2.stderr |  68 +++++++
 src/test/ui/consts/issue-64059-2.rs           |   6 +
 src/test/ui/consts/issue-64059.rs             |   1 -
 src/test/ui/issues/issue-8460-const.rs        |  12 +-
 src/test/ui/issues/issue-8460-const.stderr    | 122 +++++++++---
 src/test/ui/issues/issue-8460-const2.rs       |  59 ++++++
 src/test/ui/issues/issue-8460-const2.stderr   | 188 ++++++++++++++++++
 14 files changed, 542 insertions(+), 72 deletions(-)
 create mode 100644 src/test/ui/consts/const-err3.rs
 create mode 100644 src/test/ui/consts/const-err3.stderr
 create mode 100644 src/test/ui/consts/const-eval/promoted_errors2.rs
 create mode 100644 src/test/ui/consts/const-eval/promoted_errors2.stderr
 create mode 100644 src/test/ui/consts/issue-64059-2.rs
 create mode 100644 src/test/ui/issues/issue-8460-const2.rs
 create mode 100644 src/test/ui/issues/issue-8460-const2.stderr

diff --git a/src/test/ui/consts/const-err2.rs b/src/test/ui/consts/const-err2.rs
index cd6ac47bd92a8..ecbcc2a4b496f 100644
--- a/src/test/ui/consts/const-err2.rs
+++ b/src/test/ui/consts/const-err2.rs
@@ -5,7 +5,6 @@
 
 #![feature(rustc_attrs)]
 #![allow(exceeding_bitshifts)]
-// compile-flags: -C overflow-checks=on -O
 
 #![deny(const_err)]
 
@@ -23,7 +22,7 @@ fn main() {
     let d = 42u8 - (42u8 + 1);
     //~^ ERROR const_err
     let _e = [5u8][1];
-    //~^ ERROR const_err
+    //~^ ERROR index out of bounds
     black_box(a);
     black_box(b);
     black_box(c);
diff --git a/src/test/ui/consts/const-err2.stderr b/src/test/ui/consts/const-err2.stderr
index ecfced7f0db8b..1d84d44dc27b3 100644
--- a/src/test/ui/consts/const-err2.stderr
+++ b/src/test/ui/consts/const-err2.stderr
@@ -1,35 +1,35 @@
-error: attempt to negate with overflow
-  --> $DIR/const-err2.rs:17:13
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:16:13
    |
 LL |     let a = -std::i8::MIN;
-   |             ^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^ attempt to negate with overflow
    |
 note: lint level defined here
-  --> $DIR/const-err2.rs:10:9
+  --> $DIR/const-err2.rs:9:9
    |
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: attempt to add with overflow
-  --> $DIR/const-err2.rs:19:13
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:18:13
    |
 LL |     let b = 200u8 + 200u8 + 200u8;
-   |             ^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^ attempt to add with overflow
 
-error: attempt to multiply with overflow
-  --> $DIR/const-err2.rs:21:13
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:20:13
    |
 LL |     let c = 200u8 * 4;
-   |             ^^^^^^^^^
+   |             ^^^^^^^^^ attempt to multiply with overflow
 
-error: attempt to subtract with overflow
-  --> $DIR/const-err2.rs:23:13
+error: this expression will panic at runtime
+  --> $DIR/const-err2.rs:22:13
    |
 LL |     let d = 42u8 - (42u8 + 1);
-   |             ^^^^^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
 
 error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:25:14
+  --> $DIR/const-err2.rs:24:14
    |
 LL |     let _e = [5u8][1];
    |              ^^^^^^^^
diff --git a/src/test/ui/consts/const-err3.rs b/src/test/ui/consts/const-err3.rs
new file mode 100644
index 0000000000000..a9cf04cda7a5a
--- /dev/null
+++ b/src/test/ui/consts/const-err3.rs
@@ -0,0 +1,30 @@
+// needed because negating int::MIN will behave differently between
+// optimized compilation and unoptimized compilation and thus would
+// lead to different lints being emitted
+// compile-flags: -C overflow-checks=on -O
+
+#![feature(rustc_attrs)]
+#![allow(exceeding_bitshifts)]
+
+#![deny(const_err)]
+
+fn black_box<T>(_: T) {
+    unimplemented!()
+}
+
+fn main() {
+    let a = -std::i8::MIN;
+    //~^ ERROR const_err
+    let b = 200u8 + 200u8 + 200u8;
+    //~^ ERROR const_err
+    let c = 200u8 * 4;
+    //~^ ERROR const_err
+    let d = 42u8 - (42u8 + 1);
+    //~^ ERROR const_err
+    let _e = [5u8][1];
+    //~^ ERROR const_err
+    black_box(a);
+    black_box(b);
+    black_box(c);
+    black_box(d);
+}
diff --git a/src/test/ui/consts/const-err3.stderr b/src/test/ui/consts/const-err3.stderr
new file mode 100644
index 0000000000000..0602707be7040
--- /dev/null
+++ b/src/test/ui/consts/const-err3.stderr
@@ -0,0 +1,38 @@
+error: attempt to negate with overflow
+  --> $DIR/const-err3.rs:16:13
+   |
+LL |     let a = -std::i8::MIN;
+   |             ^^^^^^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/const-err3.rs:9:9
+   |
+LL | #![deny(const_err)]
+   |         ^^^^^^^^^
+
+error: attempt to add with overflow
+  --> $DIR/const-err3.rs:18:13
+   |
+LL |     let b = 200u8 + 200u8 + 200u8;
+   |             ^^^^^^^^^^^^^
+
+error: attempt to multiply with overflow
+  --> $DIR/const-err3.rs:20:13
+   |
+LL |     let c = 200u8 * 4;
+   |             ^^^^^^^^^
+
+error: attempt to subtract with overflow
+  --> $DIR/const-err3.rs:22:13
+   |
+LL |     let d = 42u8 - (42u8 + 1);
+   |             ^^^^^^^^^^^^^^^^^
+
+error: index out of bounds: the len is 1 but the index is 1
+  --> $DIR/const-err3.rs:24:14
+   |
+LL |     let _e = [5u8][1];
+   |              ^^^^^^^^
+
+error: aborting due to 5 previous errors
+
diff --git a/src/test/ui/consts/const-eval/promoted_errors.rs b/src/test/ui/consts/const-eval/promoted_errors.rs
index 7adb394144bdd..45941398f4b66 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.rs
+++ b/src/test/ui/consts/const-eval/promoted_errors.rs
@@ -1,12 +1,11 @@
-// compile-flags: -C overflow-checks=on -O
+// compile-flags: -O
 
 #![deny(const_err)]
 
 fn main() {
     println!("{}", 0u32 - 1);
-    //~^ ERROR attempt to subtract with overflow
     let _x = 0u32 - 1;
-    //~^ ERROR attempt to subtract with overflow
+    //~^ ERROR const_err
     println!("{}", 1/(1-1));
     //~^ ERROR attempt to divide by zero [const_err]
     //~| ERROR reaching this expression at runtime will panic or abort [const_err]
diff --git a/src/test/ui/consts/const-eval/promoted_errors.stderr b/src/test/ui/consts/const-eval/promoted_errors.stderr
index fe63d0800dd7c..40d5c73e86679 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.stderr
@@ -1,8 +1,8 @@
-error: attempt to subtract with overflow
-  --> $DIR/promoted_errors.rs:6:20
+error: this expression will panic at runtime
+  --> $DIR/promoted_errors.rs:7:14
    |
-LL |     println!("{}", 0u32 - 1);
-   |                    ^^^^^^^^
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^ attempt to subtract with overflow
    |
 note: lint level defined here
   --> $DIR/promoted_errors.rs:3:9
@@ -10,59 +10,53 @@ note: lint level defined here
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
-error: attempt to subtract with overflow
-  --> $DIR/promoted_errors.rs:8:14
-   |
-LL |     let _x = 0u32 - 1;
-   |              ^^^^^^^^
-
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:10:20
+  --> $DIR/promoted_errors.rs:9:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:10:20
+  --> $DIR/promoted_errors.rs:9:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:13:14
+  --> $DIR/promoted_errors.rs:12:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:13:14
+  --> $DIR/promoted_errors.rs:12:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:16:20
+  --> $DIR/promoted_errors.rs:15:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^
 
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_errors.rs:16:20
+  --> $DIR/promoted_errors.rs:15:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:19:14
+  --> $DIR/promoted_errors.rs:18:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:19:14
+  --> $DIR/promoted_errors.rs:18:14
    |
 LL |     let _x = 1/(false as u32);
    |              ^^^^^^^^^^^^^^^^ attempt to divide by zero
 
-error: aborting due to 10 previous errors
+error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/consts/const-eval/promoted_errors2.rs b/src/test/ui/consts/const-eval/promoted_errors2.rs
new file mode 100644
index 0000000000000..7adb394144bdd
--- /dev/null
+++ b/src/test/ui/consts/const-eval/promoted_errors2.rs
@@ -0,0 +1,22 @@
+// compile-flags: -C overflow-checks=on -O
+
+#![deny(const_err)]
+
+fn main() {
+    println!("{}", 0u32 - 1);
+    //~^ ERROR attempt to subtract with overflow
+    let _x = 0u32 - 1;
+    //~^ ERROR attempt to subtract with overflow
+    println!("{}", 1/(1-1));
+    //~^ ERROR attempt to divide by zero [const_err]
+    //~| ERROR reaching this expression at runtime will panic or abort [const_err]
+    let _x = 1/(1-1);
+    //~^ ERROR const_err
+    //~| ERROR const_err
+    println!("{}", 1/(false as u32));
+    //~^ ERROR attempt to divide by zero [const_err]
+    //~| ERROR reaching this expression at runtime will panic or abort [const_err]
+    let _x = 1/(false as u32);
+    //~^ ERROR const_err
+    //~| ERROR const_err
+}
diff --git a/src/test/ui/consts/const-eval/promoted_errors2.stderr b/src/test/ui/consts/const-eval/promoted_errors2.stderr
new file mode 100644
index 0000000000000..2819e6e8fdbe0
--- /dev/null
+++ b/src/test/ui/consts/const-eval/promoted_errors2.stderr
@@ -0,0 +1,68 @@
+error: attempt to subtract with overflow
+  --> $DIR/promoted_errors2.rs:6:20
+   |
+LL |     println!("{}", 0u32 - 1);
+   |                    ^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/promoted_errors2.rs:3:9
+   |
+LL | #![deny(const_err)]
+   |         ^^^^^^^^^
+
+error: attempt to subtract with overflow
+  --> $DIR/promoted_errors2.rs:8:14
+   |
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^
+
+error: attempt to divide by zero
+  --> $DIR/promoted_errors2.rs:10:20
+   |
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^
+
+error: reaching this expression at runtime will panic or abort
+  --> $DIR/promoted_errors2.rs:10:20
+   |
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/promoted_errors2.rs:13:14
+   |
+LL |     let _x = 1/(1-1);
+   |              ^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/promoted_errors2.rs:13:14
+   |
+LL |     let _x = 1/(1-1);
+   |              ^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/promoted_errors2.rs:16:20
+   |
+LL |     println!("{}", 1/(false as u32));
+   |                    ^^^^^^^^^^^^^^^^
+
+error: reaching this expression at runtime will panic or abort
+  --> $DIR/promoted_errors2.rs:16:20
+   |
+LL |     println!("{}", 1/(false as u32));
+   |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/promoted_errors2.rs:19:14
+   |
+LL |     let _x = 1/(false as u32);
+   |              ^^^^^^^^^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/promoted_errors2.rs:19:14
+   |
+LL |     let _x = 1/(false as u32);
+   |              ^^^^^^^^^^^^^^^^ attempt to divide by zero
+
+error: aborting due to 10 previous errors
+
diff --git a/src/test/ui/consts/issue-64059-2.rs b/src/test/ui/consts/issue-64059-2.rs
new file mode 100644
index 0000000000000..38911c3dcf692
--- /dev/null
+++ b/src/test/ui/consts/issue-64059-2.rs
@@ -0,0 +1,6 @@
+// compile-flags: -C overflow-checks=on -O
+// run-pass
+
+fn main() {
+    let _ = -(-0.0);
+}
diff --git a/src/test/ui/consts/issue-64059.rs b/src/test/ui/consts/issue-64059.rs
index 38911c3dcf692..c4c895fef66cf 100644
--- a/src/test/ui/consts/issue-64059.rs
+++ b/src/test/ui/consts/issue-64059.rs
@@ -1,4 +1,3 @@
-// compile-flags: -C overflow-checks=on -O
 // run-pass
 
 fn main() {
diff --git a/src/test/ui/issues/issue-8460-const.rs b/src/test/ui/issues/issue-8460-const.rs
index c3f53e3298b2b..611d280f774c0 100644
--- a/src/test/ui/issues/issue-8460-const.rs
+++ b/src/test/ui/issues/issue-8460-const.rs
@@ -1,5 +1,3 @@
-// compile-flags: -C overflow-checks=on -O
-
 #![deny(const_err)]
 
 use std::{isize, i8, i16, i32, i64};
@@ -8,14 +6,19 @@ use std::thread;
 fn main() {
     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
     //~^ ERROR attempt to divide with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
     //~^ ERROR attempt to divide by zero
     //~| ERROR this expression will panic at runtime
@@ -33,14 +36,19 @@ fn main() {
     //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with overflow
+    //~| ERROR this expression will panic at runtime
     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
     //~^ ERROR attempt to calculate the remainder with a divisor of zero
     //~| ERROR this expression will panic at runtime
diff --git a/src/test/ui/issues/issue-8460-const.stderr b/src/test/ui/issues/issue-8460-const.stderr
index 914323227ddd2..31b1da4f804ab 100644
--- a/src/test/ui/issues/issue-8460-const.stderr
+++ b/src/test/ui/issues/issue-8460-const.stderr
@@ -1,188 +1,248 @@
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:9:36
+  --> $DIR/issue-8460-const.rs:7:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
    |
 note: lint level defined here
-  --> $DIR/issue-8460-const.rs:3:9
+  --> $DIR/issue-8460-const.rs:1:9
    |
 LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:7:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:11:36
+  --> $DIR/issue-8460-const.rs:10:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:10:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
   --> $DIR/issue-8460-const.rs:13:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:13:36
+   |
+LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:15:36
+  --> $DIR/issue-8460-const.rs:16:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:16:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
 error: attempt to divide with overflow
-  --> $DIR/issue-8460-const.rs:17:36
+  --> $DIR/issue-8460-const.rs:19:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
-error: attempt to divide by zero
+error: this expression will panic at runtime
   --> $DIR/issue-8460-const.rs:19:36
    |
+LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to divide with overflow
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const.rs:22:36
+   |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:19:36
+  --> $DIR/issue-8460-const.rs:22:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:22:36
+  --> $DIR/issue-8460-const.rs:25:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:25:36
+  --> $DIR/issue-8460-const.rs:28:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:28:36
+  --> $DIR/issue-8460-const.rs:31:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to divide by zero
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:31:36
+  --> $DIR/issue-8460-const.rs:34:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to divide by zero
 
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:34:36
+  --> $DIR/issue-8460-const.rs:37:36
    |
 LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:37:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:36:36
+  --> $DIR/issue-8460-const.rs:40:36
    |
 LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:40:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:38:36
+  --> $DIR/issue-8460-const.rs:43:36
    |
 LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:43:36
+   |
+LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:40:36
+  --> $DIR/issue-8460-const.rs:46:36
    |
 LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:46:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with overflow
-  --> $DIR/issue-8460-const.rs:42:36
+  --> $DIR/issue-8460-const.rs:49:36
    |
 LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
    |                                    ^^^^^^^^^^^^^
 
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const.rs:49:36
+   |
+LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^ attempt to calculate the remainder with overflow
+
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:44:36
+  --> $DIR/issue-8460-const.rs:52:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:44:36
+  --> $DIR/issue-8460-const.rs:52:36
    |
 LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
    |                                    ^^^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:47:36
+  --> $DIR/issue-8460-const.rs:55:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:47:36
+  --> $DIR/issue-8460-const.rs:55:36
    |
 LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
    |                                    ^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:50:36
+  --> $DIR/issue-8460-const.rs:58:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:50:36
+  --> $DIR/issue-8460-const.rs:58:36
    |
 LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:53:36
+  --> $DIR/issue-8460-const.rs:61:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:53:36
+  --> $DIR/issue-8460-const.rs:61:36
    |
 LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
 error: attempt to calculate the remainder with a divisor of zero
-  --> $DIR/issue-8460-const.rs:56:36
+  --> $DIR/issue-8460-const.rs:64:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/issue-8460-const.rs:56:36
+  --> $DIR/issue-8460-const.rs:64:36
    |
 LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
    |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: aborting due to 30 previous errors
+error: aborting due to 40 previous errors
 
diff --git a/src/test/ui/issues/issue-8460-const2.rs b/src/test/ui/issues/issue-8460-const2.rs
new file mode 100644
index 0000000000000..c3f53e3298b2b
--- /dev/null
+++ b/src/test/ui/issues/issue-8460-const2.rs
@@ -0,0 +1,59 @@
+// compile-flags: -C overflow-checks=on -O
+
+#![deny(const_err)]
+
+use std::{isize, i8, i16, i32, i64};
+use std::thread;
+
+fn main() {
+    assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
+    //~^ ERROR attempt to divide with overflow
+    assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
+    //~^ ERROR attempt to divide with overflow
+    assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
+    //~^ ERROR attempt to divide with overflow
+    assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
+    //~^ ERROR attempt to divide with overflow
+    assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
+    //~^ ERROR attempt to divide with overflow
+    assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
+    //~^ ERROR attempt to divide by zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
+    //~^ ERROR attempt to divide by zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
+    //~^ ERROR attempt to divide by zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
+    //~^ ERROR attempt to divide by zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
+    //~^ ERROR attempt to divide by zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with overflow
+    assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with overflow
+    assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with overflow
+    assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with overflow
+    assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with overflow
+    assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with a divisor of zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with a divisor of zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with a divisor of zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with a divisor of zero
+    //~| ERROR this expression will panic at runtime
+    assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
+    //~^ ERROR attempt to calculate the remainder with a divisor of zero
+    //~| ERROR this expression will panic at runtime
+}
diff --git a/src/test/ui/issues/issue-8460-const2.stderr b/src/test/ui/issues/issue-8460-const2.stderr
new file mode 100644
index 0000000000000..b688ec1367794
--- /dev/null
+++ b/src/test/ui/issues/issue-8460-const2.stderr
@@ -0,0 +1,188 @@
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const2.rs:9:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/issue-8460-const2.rs:3:9
+   |
+LL | #![deny(const_err)]
+   |         ^^^^^^^^^
+
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const2.rs:11:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^
+
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const2.rs:13:36
+   |
+LL |     assert!(thread::spawn(move|| { i16::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const2.rs:15:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to divide with overflow
+  --> $DIR/issue-8460-const2.rs:17:36
+   |
+LL |     assert!(thread::spawn(move|| { i64::MIN / -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const2.rs:19:36
+   |
+LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
+   |                                    ^^^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:19:36
+   |
+LL |     assert!(thread::spawn(move|| { 1isize / 0; }).join().is_err());
+   |                                    ^^^^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const2.rs:22:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
+   |                                    ^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:22:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i8 / 0; }).join().is_err());
+   |                                    ^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const2.rs:25:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:25:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i16 / 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const2.rs:28:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:28:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i32 / 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to divide by zero
+
+error: attempt to divide by zero
+  --> $DIR/issue-8460-const2.rs:31:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:31:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i64 / 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to divide by zero
+
+error: attempt to calculate the remainder with overflow
+  --> $DIR/issue-8460-const2.rs:34:36
+   |
+LL |     assert!(thread::spawn(move|| { isize::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^^^
+
+error: attempt to calculate the remainder with overflow
+  --> $DIR/issue-8460-const2.rs:36:36
+   |
+LL |     assert!(thread::spawn(move|| { i8::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^
+
+error: attempt to calculate the remainder with overflow
+  --> $DIR/issue-8460-const2.rs:38:36
+   |
+LL |     assert!(thread::spawn(move|| { i16::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to calculate the remainder with overflow
+  --> $DIR/issue-8460-const2.rs:40:36
+   |
+LL |     assert!(thread::spawn(move|| { i32::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to calculate the remainder with overflow
+  --> $DIR/issue-8460-const2.rs:42:36
+   |
+LL |     assert!(thread::spawn(move|| { i64::MIN % -1; }).join().is_err());
+   |                                    ^^^^^^^^^^^^^
+
+error: attempt to calculate the remainder with a divisor of zero
+  --> $DIR/issue-8460-const2.rs:44:36
+   |
+LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
+   |                                    ^^^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:44:36
+   |
+LL |     assert!(thread::spawn(move|| { 1isize % 0; }).join().is_err());
+   |                                    ^^^^^^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: attempt to calculate the remainder with a divisor of zero
+  --> $DIR/issue-8460-const2.rs:47:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
+   |                                    ^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:47:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i8 % 0; }).join().is_err());
+   |                                    ^^^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: attempt to calculate the remainder with a divisor of zero
+  --> $DIR/issue-8460-const2.rs:50:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:50:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i16 % 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: attempt to calculate the remainder with a divisor of zero
+  --> $DIR/issue-8460-const2.rs:53:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:53:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i32 % 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: attempt to calculate the remainder with a divisor of zero
+  --> $DIR/issue-8460-const2.rs:56:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
+   |                                    ^^^^^^^^
+
+error: this expression will panic at runtime
+  --> $DIR/issue-8460-const2.rs:56:36
+   |
+LL |     assert!(thread::spawn(move|| { 1i64 % 0; }).join().is_err());
+   |                                    ^^^^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: aborting due to 30 previous errors
+

From 991f4366336820a61dd7f22e849c57d4a64b41ea Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Mon, 2 Sep 2019 15:58:05 +0200
Subject: [PATCH 15/33] Fix regex replacement in theme detection

---
 src/librustdoc/html/static/storage.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustdoc/html/static/storage.js b/src/librustdoc/html/static/storage.js
index 40a6a156972f6..eae998ca3ecbf 100644
--- a/src/librustdoc/html/static/storage.js
+++ b/src/librustdoc/html/static/storage.js
@@ -119,7 +119,7 @@ function switchTheme(styleElem, mainStyleElem, newTheme, saveTheme) {
 
 function getSystemValue() {
     var property = getComputedStyle(document.documentElement).getPropertyValue('content');
-    return property.replace(/\"\'/g, "");
+    return property.replace(/[\"\']/g, "");
 }
 
 switchTheme(currentTheme, mainTheme,

From 52c68d17d1e4b096cbb531485d5adb0c73d38185 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Tue, 27 Aug 2019 17:09:13 -0400
Subject: [PATCH 16/33] Add buffer abstraction

---
 src/librustdoc/html/format.rs | 65 +++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 313734e3fdd6b..941d2c4acb1a8 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -18,6 +18,71 @@ use crate::clean::{self, PrimitiveType};
 use crate::html::item_type::ItemType;
 use crate::html::render::{self, cache, CURRENT_DEPTH};
 
+pub trait Print {
+    fn print(&self, buffer: &mut Buffer);
+}
+
+#[derive(Debug, Clone)]
+pub struct Buffer {
+    for_html: bool,
+    buffer: String,
+}
+
+impl Buffer {
+    crate fn empty_from(v: &Buffer) -> Buffer {
+        Buffer {
+            for_html: v.for_html,
+            buffer: String::new(),
+        }
+    }
+
+    crate fn html() -> Buffer {
+        Buffer {
+            for_html: true,
+            buffer: String::new(),
+        }
+    }
+
+    crate fn is_empty(&self) -> bool {
+        self.buffer.is_empty()
+    }
+
+    crate fn into_inner(self) -> String {
+        self.buffer
+    }
+
+    crate fn insert_str(&mut self, idx: usize, s: &str) {
+        self.buffer.insert_str(idx, s);
+    }
+
+    crate fn push_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    crate fn write_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    crate fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
+        use fmt::Write;
+        self.buffer.write_fmt(v).unwrap();
+    }
+
+    crate fn display<T: fmt::Display>(&mut self, t: T) {
+        if self.for_html {
+            write!(self, "{}", t);
+        } else {
+            write!(self, "{:#}", t);
+        }
+    }
+}
+
 /// Helper to render an optional visibility with a space after it (if the
 /// visibility is preset)
 #[derive(Copy, Clone)]

From 3c83d64669ea36b1f7fcf5e53569aeb920649e91 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 30 Aug 2019 10:24:42 -0400
Subject: [PATCH 17/33] Migrate top-level rendering to Buffer

---
 src/librustdoc/html/layout.rs  |  8 ++--
 src/librustdoc/html/render.rs  | 83 +++++++++++++++++-----------------
 src/librustdoc/html/sources.rs | 10 ++--
 3 files changed, 49 insertions(+), 52 deletions(-)

diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index ae0bd1aafa8f1..2856db7ef9843 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -1,9 +1,9 @@
 use std::fmt;
-use std::io;
 use std::path::PathBuf;
 
 use crate::externalfiles::ExternalHtml;
 use crate::html::render::SlashChecker;
+use crate::html::format::Buffer;
 
 #[derive(Clone)]
 pub struct Layout {
@@ -26,7 +26,7 @@ pub struct Page<'a> {
 }
 
 pub fn render<T: fmt::Display, S: fmt::Display>(
-    dst: &mut dyn io::Write,
+    dst: &mut Buffer,
     layout: &Layout,
     page: &Page<'_>,
     sidebar: &S,
@@ -34,7 +34,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     css_file_extension: bool,
     themes: &[PathBuf],
     generate_search_filter: bool,
-) -> io::Result<()> {
+) {
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
     write!(dst,
 "<!DOCTYPE html>\
@@ -238,7 +238,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     )
 }
 
-pub fn redirect(dst: &mut dyn io::Write, url: &str) -> io::Result<()> {
+pub fn redirect(dst: &mut Buffer, url: &str) {
     // <script> triggers a redirect before refresh, so this is fine.
     write!(dst,
 r##"<!DOCTYPE html>
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index d5c47a15948fb..68168c49fa00e 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{AsyncSpace, ConstnessSpace};
+use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -1185,13 +1185,13 @@ themePicker.onblur = handleThemeButtonsBlur;
                                                 SlashChecker(s), s)
                                     })
                                     .collect::<String>());
-            let mut v = Vec::new();
-            try_err!(layout::render(&mut v, &cx.shared.layout,
-                                    &page, &(""), &content,
-                                    cx.shared.css_file_extension.is_some(),
-                                    &cx.shared.themes,
-                                    cx.shared.generate_search_filter), &dst);
-            cx.shared.fs.write(&dst, &v)?;
+            let mut v = Buffer::html();
+            layout::render(&mut v, &cx.shared.layout,
+                           &page, &(""), &content,
+                           cx.shared.css_file_extension.is_some(),
+                           &cx.shared.themes,
+                           cx.shared.generate_search_filter);
+            cx.shared.fs.write(&dst, v.into_inner().as_bytes())?;
         }
     }
 
@@ -1939,14 +1939,13 @@ impl Context {
         } else {
             String::new()
         };
-        let mut v = Vec::new();
-        try_err!(layout::render(&mut v, &self.shared.layout,
-                                &page, &sidebar, &all,
-                                self.shared.css_file_extension.is_some(),
-                                &self.shared.themes,
-                                self.shared.generate_search_filter),
-                 &final_file);
-        self.shared.fs.write(&final_file, &v)?;
+        let mut v = Buffer::html();
+        layout::render(&mut v, &self.shared.layout,
+                       &page, &sidebar, &all,
+                       self.shared.css_file_extension.is_some(),
+                       &self.shared.themes,
+                       self.shared.generate_search_filter);
+        self.shared.fs.write(&final_file, v.into_inner().as_bytes())?;
 
         // Generating settings page.
         let settings = Settings::new(self.shared.static_root_path.as_deref().unwrap_or("./"),
@@ -1959,23 +1958,24 @@ impl Context {
         let sidebar = "<p class='location'>Settings</p><div class='sidebar-elems'></div>";
         themes.push(PathBuf::from("settings.css"));
         let layout = self.shared.layout.clone();
-        let mut v = Vec::new();
-        try_err!(layout::render(&mut v, &layout,
-                                &page, &sidebar, &settings,
-                                self.shared.css_file_extension.is_some(),
-                                &themes,
-                                self.shared.generate_search_filter),
-                 &settings_file);
-        self.shared.fs.write(&settings_file, &v)?;
+        let mut v = Buffer::html();
+        layout::render(
+            &mut v,
+            &layout,
+            &page, &sidebar, &settings,
+            self.shared.css_file_extension.is_some(),
+            &themes,
+            self.shared.generate_search_filter,
+        );
+        self.shared.fs.write(&settings_file, v.into_inner().as_bytes())?;
 
         Ok(())
     }
 
     fn render_item(&self,
-                   writer: &mut dyn io::Write,
+                   writer: &mut Buffer,
                    it: &clean::Item,
-                   pushname: bool)
-                   -> io::Result<()> {
+                   pushname: bool) {
         // A little unfortunate that this is done like this, but it sure
         // does make formatting *a lot* nicer.
         CURRENT_DEPTH.with(|slot| {
@@ -2027,7 +2027,7 @@ impl Context {
                            &Item{ cx: self, item: it },
                            self.shared.css_file_extension.is_some(),
                            &self.shared.themes,
-                           self.shared.generate_search_filter)?;
+                           self.shared.generate_search_filter);
         } else {
             let mut url = self.root_path();
             if let Some(&(ref names, ty)) = cache().paths.get(&it.def_id) {
@@ -2036,10 +2036,9 @@ impl Context {
                     url.push_str("/");
                 }
                 url.push_str(&item_path(ty, names.last().unwrap()));
-                layout::redirect(writer, &url)?;
+                layout::redirect(writer, &url);
             }
         }
-        Ok(())
     }
 
     /// Non-parallelized version of rendering an item. This will take the input
@@ -2075,13 +2074,13 @@ impl Context {
 
             info!("Recursing into {}", self.dst.display());
 
-            let mut buf = Vec::new();
-            self.render_item(&mut buf, &item, false).unwrap();
+            let mut buf = Buffer::html();
+            self.render_item(&mut buf, &item, false);
             // buf will be empty if the module is stripped and there is no redirect for it
             if !buf.is_empty() {
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join("index.html");
-                scx.fs.write(&joint_dst, buf)?;
+                scx.fs.write(&joint_dst, buf.into_inner().as_bytes())?;
             }
 
             let m = match item.inner {
@@ -2110,8 +2109,8 @@ impl Context {
             self.dst = prev;
             self.current.pop().unwrap();
         } else if item.name.is_some() {
-            let mut buf = Vec::new();
-            self.render_item(&mut buf, &item, true).unwrap();
+            let mut buf = Buffer::html();
+            self.render_item(&mut buf, &item, true);
             // buf will be empty if the item is stripped and there is no redirect for it
             if !buf.is_empty() {
                 let name = item.name.as_ref().unwrap();
@@ -2119,7 +2118,7 @@ impl Context {
                 let file_name = &item_path(item_type, name);
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join(file_name);
-                self.shared.fs.write(&joint_dst, buf)?;
+                self.shared.fs.write(&joint_dst, buf.into_inner().as_bytes())?;
 
                 if !self.render_redirect_pages {
                     all.append(full_path(self, &item), &item_type);
@@ -2129,18 +2128,18 @@ impl Context {
                     // URL for the page.
                     let redir_name = format!("{}.{}.html", name, item_type.name_space());
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Vec::new();
-                    try_err!(layout::redirect(&mut v, file_name), &redir_dst);
-                    self.shared.fs.write(&redir_dst, &v)?;
+                    let mut v = Buffer::html();
+                    layout::redirect(&mut v, file_name);
+                    self.shared.fs.write(&redir_dst, v.into_inner().as_bytes())?;
                 }
                 // If the item is a macro, redirect from the old macro URL (with !)
                 // to the new one (without).
                 if item_type == ItemType::Macro {
                     let redir_name = format!("{}.{}!.html", item_type, name);
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Vec::new();
-                    try_err!(layout::redirect(&mut v, file_name), &redir_dst);
-                    self.shared.fs.write(&redir_dst, &v)?;
+                    let mut v = Buffer::html();
+                    layout::redirect(&mut v, file_name);
+                    self.shared.fs.write(&redir_dst, v.into_inner().as_bytes())?;
                 }
             }
         }
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index c1f1f59d9149a..a2a35b94c4fe7 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -4,6 +4,7 @@ use crate::fold::DocFolder;
 use crate::html::layout;
 use crate::html::render::{Error, SharedContext, BASIC_KEYWORDS};
 use crate::html::highlight;
+use crate::html::format::Buffer;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::{Component, Path, PathBuf};
@@ -105,7 +106,7 @@ impl<'a> SourceCollector<'a> {
         cur.push(&fname);
         href.push_str(&fname.to_string_lossy());
 
-        let mut v = Vec::new();
+        let mut v = Buffer::html();
         let title = format!("{} -- source", cur.file_name().expect("failed to get file name")
                                                .to_string_lossy());
         let desc = format!("Source to the Rust file `{}`.", filename);
@@ -120,15 +121,12 @@ impl<'a> SourceCollector<'a> {
             extra_scripts: &[&format!("source-files{}", self.scx.resource_suffix)],
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
-        let result = layout::render(&mut v, &self.scx.layout,
+        layout::render(&mut v, &self.scx.layout,
                        &page, &(""), &Source(contents),
                        self.scx.css_file_extension.is_some(),
                        &self.scx.themes,
                        self.scx.generate_search_filter);
-        if let Err(e) = result {
-            return Err(Error::new(e, &cur));
-        }
-        self.scx.fs.write(&cur, &v)?;
+        self.scx.fs.write(&cur, v.into_inner().as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);
         Ok(())
     }

From a076816d9488efe0919d776f4b3cbbb17e6afe35 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 30 Aug 2019 10:35:14 -0400
Subject: [PATCH 18/33] Create buffers in top-level rendering

This avoids needlessly creating and threading the buffers through when
we only use them once.
---
 src/librustdoc/html/layout.rs  | 11 ++++----
 src/librustdoc/html/render.rs  | 49 +++++++++++++++-------------------
 src/librustdoc/html/sources.rs |  6 ++---
 3 files changed, 29 insertions(+), 37 deletions(-)

diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index 2856db7ef9843..3b6d4f3b92d50 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -26,7 +26,6 @@ pub struct Page<'a> {
 }
 
 pub fn render<T: fmt::Display, S: fmt::Display>(
-    dst: &mut Buffer,
     layout: &Layout,
     page: &Page<'_>,
     sidebar: &S,
@@ -34,7 +33,8 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     css_file_extension: bool,
     themes: &[PathBuf],
     generate_search_filter: bool,
-) {
+) -> String {
+    let mut dst = Buffer::html();
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
     write!(dst,
 "<!DOCTYPE html>\
@@ -235,12 +235,13 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     } else {
         ""
     },
-    )
+    );
+    dst.into_inner()
 }
 
-pub fn redirect(dst: &mut Buffer, url: &str) {
+pub fn redirect(url: &str) -> String {
     // <script> triggers a redirect before refresh, so this is fine.
-    write!(dst,
+    format!(
 r##"<!DOCTYPE html>
 <html lang="en">
 <head>
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 68168c49fa00e..6b09d52af8504 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
+use crate::html::format::{AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -1185,13 +1185,12 @@ themePicker.onblur = handleThemeButtonsBlur;
                                                 SlashChecker(s), s)
                                     })
                                     .collect::<String>());
-            let mut v = Buffer::html();
-            layout::render(&mut v, &cx.shared.layout,
+            let v = layout::render(&cx.shared.layout,
                            &page, &(""), &content,
                            cx.shared.css_file_extension.is_some(),
                            &cx.shared.themes,
                            cx.shared.generate_search_filter);
-            cx.shared.fs.write(&dst, v.into_inner().as_bytes())?;
+            cx.shared.fs.write(&dst, v.as_bytes())?;
         }
     }
 
@@ -1939,13 +1938,12 @@ impl Context {
         } else {
             String::new()
         };
-        let mut v = Buffer::html();
-        layout::render(&mut v, &self.shared.layout,
+        let v = layout::render(&self.shared.layout,
                        &page, &sidebar, &all,
                        self.shared.css_file_extension.is_some(),
                        &self.shared.themes,
                        self.shared.generate_search_filter);
-        self.shared.fs.write(&final_file, v.into_inner().as_bytes())?;
+        self.shared.fs.write(&final_file, v.as_bytes())?;
 
         // Generating settings page.
         let settings = Settings::new(self.shared.static_root_path.as_deref().unwrap_or("./"),
@@ -1958,24 +1956,21 @@ impl Context {
         let sidebar = "<p class='location'>Settings</p><div class='sidebar-elems'></div>";
         themes.push(PathBuf::from("settings.css"));
         let layout = self.shared.layout.clone();
-        let mut v = Buffer::html();
-        layout::render(
-            &mut v,
+        let v = layout::render(
             &layout,
             &page, &sidebar, &settings,
             self.shared.css_file_extension.is_some(),
             &themes,
             self.shared.generate_search_filter,
         );
-        self.shared.fs.write(&settings_file, v.into_inner().as_bytes())?;
+        self.shared.fs.write(&settings_file, v.as_bytes())?;
 
         Ok(())
     }
 
     fn render_item(&self,
-                   writer: &mut Buffer,
                    it: &clean::Item,
-                   pushname: bool) {
+                   pushname: bool) -> String {
         // A little unfortunate that this is done like this, but it sure
         // does make formatting *a lot* nicer.
         CURRENT_DEPTH.with(|slot| {
@@ -2022,12 +2017,12 @@ impl Context {
         }
 
         if !self.render_redirect_pages {
-            layout::render(writer, &self.shared.layout, &page,
+            layout::render(&self.shared.layout, &page,
                            &Sidebar{ cx: self, item: it },
                            &Item{ cx: self, item: it },
                            self.shared.css_file_extension.is_some(),
                            &self.shared.themes,
-                           self.shared.generate_search_filter);
+                           self.shared.generate_search_filter)
         } else {
             let mut url = self.root_path();
             if let Some(&(ref names, ty)) = cache().paths.get(&it.def_id) {
@@ -2036,7 +2031,9 @@ impl Context {
                     url.push_str("/");
                 }
                 url.push_str(&item_path(ty, names.last().unwrap()));
-                layout::redirect(writer, &url);
+                layout::redirect(&url)
+            } else {
+                String::new()
             }
         }
     }
@@ -2074,13 +2071,12 @@ impl Context {
 
             info!("Recursing into {}", self.dst.display());
 
-            let mut buf = Buffer::html();
-            self.render_item(&mut buf, &item, false);
+            let buf = self.render_item(&item, false);
             // buf will be empty if the module is stripped and there is no redirect for it
             if !buf.is_empty() {
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join("index.html");
-                scx.fs.write(&joint_dst, buf.into_inner().as_bytes())?;
+                scx.fs.write(&joint_dst, buf.as_bytes())?;
             }
 
             let m = match item.inner {
@@ -2109,8 +2105,7 @@ impl Context {
             self.dst = prev;
             self.current.pop().unwrap();
         } else if item.name.is_some() {
-            let mut buf = Buffer::html();
-            self.render_item(&mut buf, &item, true);
+            let buf = self.render_item(&item, true);
             // buf will be empty if the item is stripped and there is no redirect for it
             if !buf.is_empty() {
                 let name = item.name.as_ref().unwrap();
@@ -2118,7 +2113,7 @@ impl Context {
                 let file_name = &item_path(item_type, name);
                 self.shared.ensure_dir(&self.dst)?;
                 let joint_dst = self.dst.join(file_name);
-                self.shared.fs.write(&joint_dst, buf.into_inner().as_bytes())?;
+                self.shared.fs.write(&joint_dst, buf.as_bytes())?;
 
                 if !self.render_redirect_pages {
                     all.append(full_path(self, &item), &item_type);
@@ -2128,18 +2123,16 @@ impl Context {
                     // URL for the page.
                     let redir_name = format!("{}.{}.html", name, item_type.name_space());
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Buffer::html();
-                    layout::redirect(&mut v, file_name);
-                    self.shared.fs.write(&redir_dst, v.into_inner().as_bytes())?;
+                    let v = layout::redirect(file_name);
+                    self.shared.fs.write(&redir_dst, v.as_bytes())?;
                 }
                 // If the item is a macro, redirect from the old macro URL (with !)
                 // to the new one (without).
                 if item_type == ItemType::Macro {
                     let redir_name = format!("{}.{}!.html", item_type, name);
                     let redir_dst = self.dst.join(redir_name);
-                    let mut v = Buffer::html();
-                    layout::redirect(&mut v, file_name);
-                    self.shared.fs.write(&redir_dst, v.into_inner().as_bytes())?;
+                    let v = layout::redirect(file_name);
+                    self.shared.fs.write(&redir_dst, v.as_bytes())?;
                 }
             }
         }
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index a2a35b94c4fe7..d3e006447415b 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -4,7 +4,6 @@ use crate::fold::DocFolder;
 use crate::html::layout;
 use crate::html::render::{Error, SharedContext, BASIC_KEYWORDS};
 use crate::html::highlight;
-use crate::html::format::Buffer;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::{Component, Path, PathBuf};
@@ -106,7 +105,6 @@ impl<'a> SourceCollector<'a> {
         cur.push(&fname);
         href.push_str(&fname.to_string_lossy());
 
-        let mut v = Buffer::html();
         let title = format!("{} -- source", cur.file_name().expect("failed to get file name")
                                                .to_string_lossy());
         let desc = format!("Source to the Rust file `{}`.", filename);
@@ -121,12 +119,12 @@ impl<'a> SourceCollector<'a> {
             extra_scripts: &[&format!("source-files{}", self.scx.resource_suffix)],
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
-        layout::render(&mut v, &self.scx.layout,
+        let v = layout::render(&self.scx.layout,
                        &page, &(""), &Source(contents),
                        self.scx.css_file_extension.is_some(),
                        &self.scx.themes,
                        self.scx.generate_search_filter);
-        self.scx.fs.write(&cur, v.into_inner().as_bytes())?;
+        self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);
         Ok(())
     }

From 8850cb599de263f8163756ba85c334e4ec50077b Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 30 Aug 2019 10:41:56 -0400
Subject: [PATCH 19/33] Remove needless clone of layout

---
 src/librustdoc/html/render.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 6b09d52af8504..02c080204eb5a 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -1955,9 +1955,8 @@ impl Context {
         let mut themes = self.shared.themes.clone();
         let sidebar = "<p class='location'>Settings</p><div class='sidebar-elems'></div>";
         themes.push(PathBuf::from("settings.css"));
-        let layout = self.shared.layout.clone();
         let v = layout::render(
-            &layout,
+            &self.shared.layout,
             &page, &sidebar, &settings,
             self.shared.css_file_extension.is_some(),
             &themes,

From a3539f9ee8c6ec0f9b4b27a86b3313121359da50 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 30 Aug 2019 10:51:13 -0400
Subject: [PATCH 20/33] Move constant parameters to render to Layout struct

---
 src/librustdoc/html/layout.rs  | 12 ++++++++----
 src/librustdoc/html/render.rs  | 29 +++++++----------------------
 src/librustdoc/html/sources.rs |  4 +---
 3 files changed, 16 insertions(+), 29 deletions(-)

diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index 3b6d4f3b92d50..cf55b9ad34308 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -11,6 +11,12 @@ pub struct Layout {
     pub favicon: String,
     pub external_html: ExternalHtml,
     pub krate: String,
+    /// The given user css file which allow to customize the generated
+    /// documentation theme.
+    pub css_file_extension: Option<PathBuf>,
+    /// If false, the `select` element to have search filtering by crates on rendered docs
+    /// won't be generated.
+    pub generate_search_filter: bool,
 }
 
 pub struct Page<'a> {
@@ -30,9 +36,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     page: &Page<'_>,
     sidebar: &S,
     t: &T,
-    css_file_extension: bool,
     themes: &[PathBuf],
-    generate_search_filter: bool,
 ) -> String {
     let mut dst = Buffer::html();
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
@@ -164,7 +168,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     <script defer src=\"{root_path}search-index{suffix}.js\"></script>\
 </body>\
 </html>",
-    css_extension = if css_file_extension {
+    css_extension = if layout.css_file_extension.is_some() {
         format!("<link rel=\"stylesheet\" \
                        type=\"text/css\" \
                        href=\"{static_root_path}theme{suffix}.css\">",
@@ -228,7 +232,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
                 root_path=page.root_path,
                 extra_script=e)
     }).collect::<String>(),
-    filter_crates=if generate_search_filter {
+    filter_crates=if layout.generate_search_filter {
         "<select id=\"crate-search\">\
             <option value=\"All crates\">All crates</option>\
         </select>"
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 02c080204eb5a..ec0294f583681 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -192,9 +192,6 @@ crate struct SharedContext {
     /// The base-URL of the issue tracker for when an item has been tagged with
     /// an issue number.
     pub issue_tracker_base_url: Option<String>,
-    /// The given user css file which allow to customize the generated
-    /// documentation theme.
-    pub css_file_extension: Option<PathBuf>,
     /// The directories that have already been created in this doc run. Used to reduce the number
     /// of spurious `create_dir_all` calls.
     pub created_dirs: RefCell<FxHashSet<PathBuf>>,
@@ -209,9 +206,6 @@ crate struct SharedContext {
     /// Optional path string to be used to load static files on output pages. If not set, uses
     /// combinations of `../` to reach the documentation root.
     pub static_root_path: Option<String>,
-    /// If false, the `select` element to have search filtering by crates on rendered docs
-    /// won't be generated.
-    pub generate_search_filter: bool,
     /// Option disabled by default to generate files used by RLS and some other tools.
     pub generate_redirect_pages: bool,
     /// The fs handle we are working with.
@@ -545,14 +539,14 @@ pub fn run(mut krate: clean::Crate,
             favicon: String::new(),
             external_html,
             krate: krate.name.clone(),
+            css_file_extension: extension_css,
+            generate_search_filter,
         },
-        css_file_extension: extension_css,
         created_dirs: Default::default(),
         sort_modules_alphabetically,
         themes,
         resource_suffix,
         static_root_path,
-        generate_search_filter,
         generate_redirect_pages,
         fs: DocFS::new(&errors),
     };
@@ -932,7 +926,7 @@ themePicker.onblur = handleThemeButtonsBlur;
             options.enable_minification)?;
     }
 
-    if let Some(ref css) = cx.shared.css_file_extension {
+    if let Some(ref css) = cx.shared.layout.css_file_extension {
         let out = cx.dst.join(&format!("theme{}.css", cx.shared.resource_suffix));
         let buffer = try_err!(fs::read_to_string(css), css);
         if !options.enable_minification {
@@ -1187,9 +1181,7 @@ themePicker.onblur = handleThemeButtonsBlur;
                                     .collect::<String>());
             let v = layout::render(&cx.shared.layout,
                            &page, &(""), &content,
-                           cx.shared.css_file_extension.is_some(),
-                           &cx.shared.themes,
-                           cx.shared.generate_search_filter);
+                           &cx.shared.themes);
             cx.shared.fs.write(&dst, v.as_bytes())?;
         }
     }
@@ -1940,9 +1932,7 @@ impl Context {
         };
         let v = layout::render(&self.shared.layout,
                        &page, &sidebar, &all,
-                       self.shared.css_file_extension.is_some(),
-                       &self.shared.themes,
-                       self.shared.generate_search_filter);
+                       &self.shared.themes);
         self.shared.fs.write(&final_file, v.as_bytes())?;
 
         // Generating settings page.
@@ -1958,10 +1948,7 @@ impl Context {
         let v = layout::render(
             &self.shared.layout,
             &page, &sidebar, &settings,
-            self.shared.css_file_extension.is_some(),
-            &themes,
-            self.shared.generate_search_filter,
-        );
+            &themes);
         self.shared.fs.write(&settings_file, v.as_bytes())?;
 
         Ok(())
@@ -2019,9 +2006,7 @@ impl Context {
             layout::render(&self.shared.layout, &page,
                            &Sidebar{ cx: self, item: it },
                            &Item{ cx: self, item: it },
-                           self.shared.css_file_extension.is_some(),
-                           &self.shared.themes,
-                           self.shared.generate_search_filter)
+                           &self.shared.themes)
         } else {
             let mut url = self.root_path();
             if let Some(&(ref names, ty)) = cache().paths.get(&it.def_id) {
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index d3e006447415b..018db3f9363cb 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -121,9 +121,7 @@ impl<'a> SourceCollector<'a> {
         };
         let v = layout::render(&self.scx.layout,
                        &page, &(""), &Source(contents),
-                       self.scx.css_file_extension.is_some(),
-                       &self.scx.themes,
-                       self.scx.generate_search_filter);
+                       &self.scx.themes);
         self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);
         Ok(())

From d8697481e98715db86523c14befd59e8e33e040a Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 08:45:44 -0400
Subject: [PATCH 21/33] Replace writeln!/write! with push_str

---
 src/librustdoc/html/render.rs | 150 ++++++++++++++++------------------
 1 file changed, 69 insertions(+), 81 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index ec0294f583681..c52925f8f7781 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{AsyncSpace, ConstnessSpace};
+use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -1025,12 +1025,12 @@ themePicker.onblur = handleThemeButtonsBlur;
         }
         all_aliases.push(format!("ALIASES[\"{}\"] = {{{}}};", krate.name, output));
         all_aliases.sort();
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "var ALIASES = {{}};"), &dst);
+        let mut v = Buffer::html();
+        writeln!(&mut v, "var ALIASES = {{}};");
         for aliases in &all_aliases {
-            try_err!(writeln!(&mut v, "{}", aliases), &dst);
+            writeln!(&mut v, "{}", aliases);
         }
-        cx.shared.fs.write(&dst, &v)?;
+        cx.shared.fs.write(&dst, v.into_inner().into_bytes())?;
     }
 
     use std::ffi::OsString;
@@ -1114,12 +1114,9 @@ themePicker.onblur = handleThemeButtonsBlur;
                                  &krate.name,
                                  hierarchy.to_json_string()));
         all_sources.sort();
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v,
-                          "var N = null;var sourcesIndex = {{}};\n{}\ncreateSourceSidebar();",
-                          all_sources.join("\n")),
-                 &dst);
-        cx.shared.fs.write(&dst, &v)?;
+        let v = format!("var N = null;var sourcesIndex = {{}};\n{}\ncreateSourceSidebar();\n",
+                          all_sources.join("\n"));
+        cx.shared.fs.write(&dst, v.as_bytes())?;
     }
 
     // Update the search index
@@ -1134,14 +1131,11 @@ themePicker.onblur = handleThemeButtonsBlur;
     // with rustdoc running in parallel.
     all_indexes.sort();
     {
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "var N=null,E=\"\",T=\"t\",U=\"u\",searchIndex={{}};"), &dst);
-        try_err!(write_minify_replacer(
-            &mut v,
+        let mut v = String::from("var N=null,E=\"\",T=\"t\",U=\"u\",searchIndex={{}};\n");
+        v.push_str(&minify_replacer(
             &format!("{}\n{}", variables.join(""), all_indexes.join("\n")),
-            options.enable_minification),
-            &dst);
-        try_err!(write!(&mut v, "initSearch(searchIndex);addSearchOptions(searchIndex);"), &dst);
+            options.enable_minification));
+        v.push_str("initSearch(searchIndex);addSearchOptions(searchIndex);");
         cx.shared.fs.write(&dst, &v)?;
     }
     if options.enable_index_page {
@@ -1247,19 +1241,18 @@ themePicker.onblur = handleThemeButtonsBlur;
         // identically even with rustdoc running in parallel.
         all_implementors.sort();
 
-        let mut v = Vec::new();
-        try_err!(writeln!(&mut v, "(function() {{var implementors = {{}};"), &mydst);
+        let mut v = String::from("(function() {var implementors = {}};\n");
         for implementor in &all_implementors {
-            try_err!(writeln!(&mut v, "{}", *implementor), &mydst);
+            v.push_str(&format!("{}", *implementor));
         }
-        try_err!(writeln!(&mut v, "{}", r"
+        v.push_str(r"
             if (window.register_implementors) {
                 window.register_implementors(implementors);
             } else {
                 window.pending_implementors = implementors;
             }
-        "), &mydst);
-        try_err!(writeln!(&mut v, r"}})()"), &mydst);
+        \n");
+        v.push_str("})()");
         cx.shared.fs.write(&mydst, &v)?;
     }
     Ok(())
@@ -1279,68 +1272,65 @@ fn write_minify(fs:&DocFS, dst: PathBuf, contents: &str, enable_minification: bo
     }
 }
 
-fn write_minify_replacer<W: Write>(
-    dst: &mut W,
+fn minify_replacer(
     contents: &str,
     enable_minification: bool,
-) -> io::Result<()> {
+) -> String {
     use minifier::js::{simple_minify, Keyword, ReservedChar, Token, Tokens};
 
     if enable_minification {
-        writeln!(dst, "{}",
-                 {
-                    let tokens: Tokens<'_> = simple_minify(contents)
-                        .into_iter()
-                        .filter(|(f, next)| {
-                            // We keep backlines.
-                            minifier::js::clean_token_except(f, next, &|c: &Token<'_>| {
-                                c.get_char() != Some(ReservedChar::Backline)
-                            })
-                        })
-                        .map(|(f, _)| {
-                            minifier::js::replace_token_with(f, &|t: &Token<'_>| {
-                                match *t {
-                                    Token::Keyword(Keyword::Null) => Some(Token::Other("N")),
-                                    Token::String(s) => {
-                                        let s = &s[1..s.len() -1]; // The quotes are included
-                                        if s.is_empty() {
-                                            Some(Token::Other("E"))
-                                        } else if s == "t" {
-                                            Some(Token::Other("T"))
-                                        } else if s == "u" {
-                                            Some(Token::Other("U"))
-                                        } else {
-                                            None
-                                        }
-                                    }
-                                    _ => None,
-                                }
-                            })
-                        })
-                        .collect::<Vec<_>>()
-                        .into();
-                    tokens.apply(|f| {
-                        // We add a backline after the newly created variables.
-                        minifier::js::aggregate_strings_into_array_with_separation_filter(
-                            f,
-                            "R",
-                            Token::Char(ReservedChar::Backline),
-                            // This closure prevents crates' names from being aggregated.
-                            //
-                            // The point here is to check if the string is preceded by '[' and
-                            // "searchIndex". If so, it means this is a crate name and that it
-                            // shouldn't be aggregated.
-                            |tokens, pos| {
-                                pos < 2 ||
-                                !tokens[pos - 1].eq_char(ReservedChar::OpenBracket) ||
-                                tokens[pos - 2].get_other() != Some("searchIndex")
+        let tokens: Tokens<'_> = simple_minify(contents)
+            .into_iter()
+            .filter(|(f, next)| {
+                // We keep backlines.
+                minifier::js::clean_token_except(f, next, &|c: &Token<'_>| {
+                    c.get_char() != Some(ReservedChar::Backline)
+                })
+            })
+            .map(|(f, _)| {
+                minifier::js::replace_token_with(f, &|t: &Token<'_>| {
+                    match *t {
+                        Token::Keyword(Keyword::Null) => Some(Token::Other("N")),
+                        Token::String(s) => {
+                            let s = &s[1..s.len() -1]; // The quotes are included
+                            if s.is_empty() {
+                                Some(Token::Other("E"))
+                            } else if s == "t" {
+                                Some(Token::Other("T"))
+                            } else if s == "u" {
+                                Some(Token::Other("U"))
+                            } else {
+                                None
                             }
-                        )
-                    })
-                    .to_string()
+                        }
+                        _ => None,
+                    }
                 })
+            })
+            .collect::<Vec<_>>()
+            .into();
+        let o = tokens.apply(|f| {
+            // We add a backline after the newly created variables.
+            minifier::js::aggregate_strings_into_array_with_separation_filter(
+                f,
+                "R",
+                Token::Char(ReservedChar::Backline),
+                // This closure prevents crates' names from being aggregated.
+                //
+                // The point here is to check if the string is preceded by '[' and
+                // "searchIndex". If so, it means this is a crate name and that it
+                // shouldn't be aggregated.
+                |tokens, pos| {
+                    pos < 2 ||
+                    !tokens[pos - 1].eq_char(ReservedChar::OpenBracket) ||
+                    tokens[pos - 2].get_other() != Some("searchIndex")
+                }
+            )
+        })
+        .to_string();
+        format!("{}\n", o)
     } else {
-        writeln!(dst, "{}", contents)
+        format!("{}\n", contents)
     }
 }
 
@@ -2073,9 +2063,7 @@ impl Context {
             if !self.render_redirect_pages {
                 let items = self.build_sidebar_items(&m);
                 let js_dst = self.dst.join("sidebar-items.js");
-                let mut v = Vec::new();
-                try_err!(write!(&mut v, "initSidebarItems({});",
-                                as_json(&items)), &js_dst);
+                let v = format!("initSidebarItems({});", as_json(&items));
                 scx.fs.write(&js_dst, &v)?;
             }
 

From 14fcaa1af2715724bccabb0b4a6e5e36d2f6e21f Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 08:52:04 -0400
Subject: [PATCH 22/33] Remove unnecessary Buffer in layout::render

---
 src/librustdoc/html/layout.rs | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index cf55b9ad34308..c7b6684fd3110 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -3,7 +3,6 @@ use std::path::PathBuf;
 
 use crate::externalfiles::ExternalHtml;
 use crate::html::render::SlashChecker;
-use crate::html::format::Buffer;
 
 #[derive(Clone)]
 pub struct Layout {
@@ -38,10 +37,8 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     t: &T,
     themes: &[PathBuf],
 ) -> String {
-    let mut dst = Buffer::html();
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
-    write!(dst,
-"<!DOCTYPE html>\
+    format!("<!DOCTYPE html>\
 <html lang=\"en\">\
 <head>\
     <meta charset=\"utf-8\">\
@@ -239,8 +236,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     } else {
         ""
     },
-    );
-    dst.into_inner()
+    )
 }
 
 pub fn redirect(url: &str) -> String {

From ca2801f30445a204ff3a60a7b3f610586fad5301 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 09:07:29 -0400
Subject: [PATCH 23/33] Move sidebar to Buffer-printing

---
 src/librustdoc/html/format.rs |  23 ++++++++
 src/librustdoc/html/layout.rs |   5 +-
 src/librustdoc/html/render.rs | 104 ++++++++++++++--------------------
 3 files changed, 70 insertions(+), 62 deletions(-)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 941d2c4acb1a8..99ddbcd7170d7 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -22,6 +22,24 @@ pub trait Print {
     fn print(&self, buffer: &mut Buffer);
 }
 
+impl<T: ?Sized + Print> Print for &'_ T {
+    fn print(&self, buffer: &mut Buffer) {
+        (&**self).print(buffer)
+    }
+}
+
+impl Print for String {
+    fn print(&self, buffer: &mut Buffer) {
+        buffer.write_str(self);
+    }
+}
+
+impl Print for str {
+    fn print(&self, buffer: &mut Buffer) {
+        buffer.write_str(self);
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Buffer {
     for_html: bool,
@@ -74,6 +92,11 @@ impl Buffer {
         self.buffer.write_fmt(v).unwrap();
     }
 
+    crate fn to_display<T: ?Sized + Print>(mut self, t: &T) -> String {
+        t.print(&mut self);
+        self.into_inner()
+    }
+
     crate fn display<T: fmt::Display>(&mut self, t: T) {
         if self.for_html {
             write!(self, "{}", t);
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index c7b6684fd3110..38dcfbfcec49c 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -3,6 +3,7 @@ use std::path::PathBuf;
 
 use crate::externalfiles::ExternalHtml;
 use crate::html::render::SlashChecker;
+use crate::html::format::{Buffer, Print};
 
 #[derive(Clone)]
 pub struct Layout {
@@ -30,7 +31,7 @@ pub struct Page<'a> {
     pub static_extra_scripts: &'a [&'a str],
 }
 
-pub fn render<T: fmt::Display, S: fmt::Display>(
+pub fn render<T: fmt::Display, S: Print>(
     layout: &Layout,
     page: &Page<'_>,
     sidebar: &S,
@@ -208,7 +209,7 @@ pub fn render<T: fmt::Display, S: fmt::Display>(
     in_header = layout.external_html.in_header,
     before_content = layout.external_html.before_content,
     after_content = layout.external_html.after_content,
-    sidebar   = *sidebar,
+    sidebar   = Buffer::html().to_display(sidebar),
     krate     = layout.krate,
     themes = themes.iter()
                    .filter_map(|t| t.file_stem())
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index c52925f8f7781..dce50b05a5b01 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
+use crate::html::format::{Print, Buffer, AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -4266,15 +4266,15 @@ fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item)
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-impl<'a> fmt::Display for Sidebar<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl Print for Sidebar<'_> {
+    fn print(&self, buffer: &mut Buffer) {
         let cx = self.cx;
         let it = self.item;
         let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
 
         if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
             || it.is_enum() || it.is_mod() || it.is_typedef() {
-            write!(fmt, "<p class='location'>{}{}</p>",
+            write!(buffer, "<p class='location'>{}{}</p>",
                 match it.inner {
                     clean::StructItem(..) => "Struct ",
                     clean::TraitItem(..) => "Trait ",
@@ -4290,33 +4290,33 @@ impl<'a> fmt::Display for Sidebar<'a> {
                     },
                     _ => "",
                 },
-                it.name.as_ref().unwrap())?;
+                it.name.as_ref().unwrap());
         }
 
         if it.is_crate() {
             if let Some(ref version) = cache().crate_version {
-                write!(fmt,
+                write!(buffer,
                        "<div class='block version'>\
                         <p>Version {}</p>\
                         </div>",
-                       version)?;
+                       version);
             }
         }
 
-        write!(fmt, "<div class=\"sidebar-elems\">")?;
+        write!(buffer, "<div class=\"sidebar-elems\">");
         if it.is_crate() {
-            write!(fmt, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
-                   it.name.as_ref().expect("crates always have a name"))?;
+            write!(buffer, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
+                   it.name.as_ref().expect("crates always have a name"));
         }
         match it.inner {
-            clean::StructItem(ref s) => sidebar_struct(fmt, it, s)?,
-            clean::TraitItem(ref t) => sidebar_trait(fmt, it, t)?,
-            clean::PrimitiveItem(ref p) => sidebar_primitive(fmt, it, p)?,
-            clean::UnionItem(ref u) => sidebar_union(fmt, it, u)?,
-            clean::EnumItem(ref e) => sidebar_enum(fmt, it, e)?,
-            clean::TypedefItem(ref t, _) => sidebar_typedef(fmt, it, t)?,
-            clean::ModuleItem(ref m) => sidebar_module(fmt, it, &m.items)?,
-            clean::ForeignTypeItem => sidebar_foreign_type(fmt, it)?,
+            clean::StructItem(ref s) => sidebar_struct(buffer, it, s),
+            clean::TraitItem(ref t) => sidebar_trait(buffer, it, t),
+            clean::PrimitiveItem(ref p) => sidebar_primitive(buffer, it, p),
+            clean::UnionItem(ref u) => sidebar_union(buffer, it, u),
+            clean::EnumItem(ref e) => sidebar_enum(buffer, it, e),
+            clean::TypedefItem(ref t, _) => sidebar_typedef(buffer, it, t),
+            clean::ModuleItem(ref m) => sidebar_module(buffer, it, &m.items),
+            clean::ForeignTypeItem => sidebar_foreign_type(buffer, it),
             _ => (),
         }
 
@@ -4328,20 +4328,20 @@ impl<'a> fmt::Display for Sidebar<'a> {
         // as much HTML as possible in order to allow non-JS-enabled browsers
         // to navigate the documentation (though slightly inefficiently).
 
-        write!(fmt, "<p class='location'>")?;
+        write!(buffer, "<p class='location'>");
         for (i, name) in cx.current.iter().take(parentlen).enumerate() {
             if i > 0 {
-                write!(fmt, "::<wbr>")?;
+                write!(buffer, "::<wbr>");
             }
-            write!(fmt, "<a href='{}index.html'>{}</a>",
+            write!(buffer, "<a href='{}index.html'>{}</a>",
                    &cx.root_path()[..(cx.current.len() - i - 1) * 3],
-                   *name)?;
+                   *name);
         }
-        write!(fmt, "</p>")?;
+        write!(buffer, "</p>");
 
         // Sidebar refers to the enclosing module, not this module.
         let relpath = if it.is_mod() { "../" } else { "" };
-        write!(fmt,
+        write!(buffer,
                "<script>window.sidebarCurrent = {{\
                    name: '{name}', \
                    ty: '{ty}', \
@@ -4349,18 +4349,16 @@ impl<'a> fmt::Display for Sidebar<'a> {
                 }};</script>",
                name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
                ty = it.type_().css_class(),
-               path = relpath)?;
+               path = relpath);
         if parentlen == 0 {
             // There is no sidebar-items.js beyond the crate root path
             // FIXME maybe dynamic crate loading can be merged here
         } else {
-            write!(fmt, "<script defer src=\"{path}sidebar-items.js\"></script>",
-                   path = relpath)?;
+            write!(buffer, "<script defer src=\"{path}sidebar-items.js\"></script>",
+                   path = relpath);
         }
         // Closes sidebar-elems div.
-        write!(fmt, "</div>")?;
-
-        Ok(())
+        write!(buffer, "</div>");
     }
 }
 
@@ -4534,8 +4532,7 @@ fn sidebar_assoc_items(it: &clean::Item) -> String {
     out
 }
 
-fn sidebar_struct(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                  s: &clean::Struct) -> fmt::Result {
+fn sidebar_struct(buf: &mut Buffer, it: &clean::Item, s: &clean::Struct) {
     let mut sidebar = String::new();
     let fields = get_struct_fields_name(&s.fields);
 
@@ -4549,9 +4546,8 @@ fn sidebar_struct(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn get_id_for_impl_on_foreign_type(for_: &clean::Type, trait_: &clean::Type) -> String {
@@ -4575,8 +4571,7 @@ fn is_negative_impl(i: &clean::Impl) -> bool {
     i.polarity == Some(clean::ImplPolarity::Negative)
 }
 
-fn sidebar_trait(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                 t: &clean::Trait) -> fmt::Result {
+fn sidebar_trait(buf: &mut Buffer, it: &clean::Item, t: &clean::Trait) {
     let mut sidebar = String::new();
 
     let types = t.items
@@ -4684,27 +4679,23 @@ fn sidebar_trait(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
 
     sidebar.push_str(&sidebar_assoc_items(it));
 
-    write!(fmt, "<div class=\"block items\">{}</div>", sidebar)
+    write!(buf, "<div class=\"block items\">{}</div>", sidebar)
 }
 
-fn sidebar_primitive(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                     _p: &clean::PrimitiveType) -> fmt::Result {
+fn sidebar_primitive(buf: &mut Buffer, it: &clean::Item, _p: &clean::PrimitiveType) {
     let sidebar = sidebar_assoc_items(it);
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_typedef(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                   _t: &clean::Typedef) -> fmt::Result {
+fn sidebar_typedef(buf: &mut Buffer, it: &clean::Item, _t: &clean::Typedef) {
     let sidebar = sidebar_assoc_items(it);
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn get_struct_fields_name(fields: &[clean::Item]) -> String {
@@ -4722,8 +4713,7 @@ fn get_struct_fields_name(fields: &[clean::Item]) -> String {
           .collect()
 }
 
-fn sidebar_union(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                 u: &clean::Union) -> fmt::Result {
+fn sidebar_union(buf: &mut Buffer, it: &clean::Item, u: &clean::Union) {
     let mut sidebar = String::new();
     let fields = get_struct_fields_name(&u.fields);
 
@@ -4735,13 +4725,11 @@ fn sidebar_union(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_enum(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
-                e: &clean::Enum) -> fmt::Result {
+fn sidebar_enum(buf: &mut Buffer, it: &clean::Item, e: &clean::Enum) {
     let mut sidebar = String::new();
 
     let variants = e.variants.iter()
@@ -4759,9 +4747,8 @@ fn sidebar_enum(fmt: &mut fmt::Formatter<'_>, it: &clean::Item,
     sidebar.push_str(&sidebar_assoc_items(it));
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn item_ty_to_strs(ty: &ItemType) -> (&'static str, &'static str) {
@@ -4795,8 +4782,7 @@ fn item_ty_to_strs(ty: &ItemType) -> (&'static str, &'static str) {
     }
 }
 
-fn sidebar_module(fmt: &mut fmt::Formatter<'_>, _it: &clean::Item,
-                  items: &[clean::Item]) -> fmt::Result {
+fn sidebar_module(buf: &mut Buffer, _it: &clean::Item, items: &[clean::Item]) {
     let mut sidebar = String::new();
 
     if items.iter().any(|it| it.type_() == ItemType::ExternCrate ||
@@ -4823,17 +4809,15 @@ fn sidebar_module(fmt: &mut fmt::Formatter<'_>, _it: &clean::Item,
     }
 
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\"><ul>{}</ul></div>", sidebar)?;
+        write!(buf, "<div class=\"block items\"><ul>{}</ul></div>", sidebar);
     }
-    Ok(())
 }
 
-fn sidebar_foreign_type(fmt: &mut fmt::Formatter<'_>, it: &clean::Item) -> fmt::Result {
+fn sidebar_foreign_type(buf: &mut Buffer, it: &clean::Item) {
     let sidebar = sidebar_assoc_items(it);
     if !sidebar.is_empty() {
-        write!(fmt, "<div class=\"block items\">{}</div>", sidebar)?;
+        write!(buf, "<div class=\"block items\">{}</div>", sidebar);
     }
-    Ok(())
 }
 
 fn item_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,

From 23679759411f313e858cd2edf8cf1b1ad588dc32 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 11:22:51 -0400
Subject: [PATCH 24/33] Implement Print for FnOnce(&mut Buffer)

This means that callers can pass in a closure like
`|buf| some_function(..., &mut buf)` and pass in arbitrary arguments to
that function without complicating the trait definition. We also keep
the impl for str and String, since it's useful to be able to just pass
in "" or format!("{}"...) results in some cases.

This changes Print's definition to take self, instead of &self, because
otherwise FnOnce cannot be called directly. We could instead take FnMut
or even Fn, but that seems like it'd merely complicate matters -- most
of the time, the FnOnce does not constrain us at all anyway. If it does,
a custom Print impl for &'_ SomeStruct is not all that painful.
---
 src/librustdoc/html/format.rs  | 20 +++++++++++---------
 src/librustdoc/html/layout.rs  |  2 +-
 src/librustdoc/html/render.rs  | 10 +++++-----
 src/librustdoc/html/sources.rs |  2 +-
 4 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 99ddbcd7170d7..5d86f0566111f 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -19,23 +19,25 @@ use crate::html::item_type::ItemType;
 use crate::html::render::{self, cache, CURRENT_DEPTH};
 
 pub trait Print {
-    fn print(&self, buffer: &mut Buffer);
+    fn print(self, buffer: &mut Buffer);
 }
 
-impl<T: ?Sized + Print> Print for &'_ T {
-    fn print(&self, buffer: &mut Buffer) {
-        (&**self).print(buffer)
+impl<F> Print for F
+    where F: FnOnce(&mut Buffer),
+{
+    fn print(self, buffer: &mut Buffer) {
+        (self)(buffer)
     }
 }
 
 impl Print for String {
-    fn print(&self, buffer: &mut Buffer) {
-        buffer.write_str(self);
+    fn print(self, buffer: &mut Buffer) {
+        buffer.write_str(&self);
     }
 }
 
-impl Print for str {
-    fn print(&self, buffer: &mut Buffer) {
+impl Print for &'_ str {
+    fn print(self, buffer: &mut Buffer) {
         buffer.write_str(self);
     }
 }
@@ -92,7 +94,7 @@ impl Buffer {
         self.buffer.write_fmt(v).unwrap();
     }
 
-    crate fn to_display<T: ?Sized + Print>(mut self, t: &T) -> String {
+    crate fn to_display<T: Print>(mut self, t: T) -> String {
         t.print(&mut self);
         self.into_inner()
     }
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index 38dcfbfcec49c..1202f411f912c 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -34,7 +34,7 @@ pub struct Page<'a> {
 pub fn render<T: fmt::Display, S: Print>(
     layout: &Layout,
     page: &Page<'_>,
-    sidebar: &S,
+    sidebar: S,
     t: &T,
     themes: &[PathBuf],
 ) -> String {
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index dce50b05a5b01..1286f9db15efd 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -1174,7 +1174,7 @@ themePicker.onblur = handleThemeButtonsBlur;
                                     })
                                     .collect::<String>());
             let v = layout::render(&cx.shared.layout,
-                           &page, &(""), &content,
+                           &page, "", &content,
                            &cx.shared.themes);
             cx.shared.fs.write(&dst, v.as_bytes())?;
         }
@@ -1921,7 +1921,7 @@ impl Context {
             String::new()
         };
         let v = layout::render(&self.shared.layout,
-                       &page, &sidebar, &all,
+                       &page, sidebar, &all,
                        &self.shared.themes);
         self.shared.fs.write(&final_file, v.as_bytes())?;
 
@@ -1937,7 +1937,7 @@ impl Context {
         themes.push(PathBuf::from("settings.css"));
         let v = layout::render(
             &self.shared.layout,
-            &page, &sidebar, &settings,
+            &page, sidebar, &settings,
             &themes);
         self.shared.fs.write(&settings_file, v.as_bytes())?;
 
@@ -1994,7 +1994,7 @@ impl Context {
 
         if !self.render_redirect_pages {
             layout::render(&self.shared.layout, &page,
-                           &Sidebar{ cx: self, item: it },
+                           Sidebar{ cx: self, item: it },
                            &Item{ cx: self, item: it },
                            &self.shared.themes)
         } else {
@@ -4267,7 +4267,7 @@ fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item)
 }
 
 impl Print for Sidebar<'_> {
-    fn print(&self, buffer: &mut Buffer) {
+    fn print(self, buffer: &mut Buffer) {
         let cx = self.cx;
         let it = self.item;
         let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index 018db3f9363cb..94ae14226097f 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -120,7 +120,7 @@ impl<'a> SourceCollector<'a> {
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
         let v = layout::render(&self.scx.layout,
-                       &page, &(""), &Source(contents),
+                       &page, "", &Source(contents),
                        &self.scx.themes);
         self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);

From 8c06e79cdaf4a39a0a14b8da6a9b4610ee94e254 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 11:32:47 -0400
Subject: [PATCH 25/33] Delete Sidebar struct in favor of FnOnce impl

---
 src/librustdoc/html/render.rs | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 1286f9db15efd..849121a0e0d87 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -387,8 +387,6 @@ struct Item<'a> {
     item: &'a clean::Item,
 }
 
-struct Sidebar<'a> { cx: &'a Context, item: &'a clean::Item, }
-
 /// Struct representing one entry in the JS search index. These are all emitted
 /// by hand to a large JS file at the end of cache-creation.
 #[derive(Debug)]
@@ -1994,7 +1992,7 @@ impl Context {
 
         if !self.render_redirect_pages {
             layout::render(&self.shared.layout, &page,
-                           Sidebar{ cx: self, item: it },
+                           |buf: &mut _| print_sidebar(self, it, buf),
                            &Item{ cx: self, item: it },
                            &self.shared.themes)
         } else {
@@ -4266,10 +4264,7 @@ fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item)
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-impl Print for Sidebar<'_> {
-    fn print(self, buffer: &mut Buffer) {
-        let cx = self.cx;
-        let it = self.item;
+    fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
         let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
 
         if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
@@ -4360,7 +4355,6 @@ impl Print for Sidebar<'_> {
         // Closes sidebar-elems div.
         write!(buffer, "</div>");
     }
-}
 
 fn get_next_url(used_links: &mut FxHashSet<String>, url: String) -> String {
     if used_links.insert(url.clone()) {

From 6ab9b3232d42884c0559133c100a67a513622d68 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 11:34:37 -0400
Subject: [PATCH 26/33] De-indent all fmt::Display impls for later replacement
 to functions

---
 src/librustdoc/html/format.rs  |  10 +-
 src/librustdoc/html/render.rs  | 466 ++++++++++++++++-----------------
 src/librustdoc/html/sources.rs |  34 +--
 3 files changed, 255 insertions(+), 255 deletions(-)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 5d86f0566111f..f3c40c8568bb6 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -290,11 +290,11 @@ impl<'a> fmt::Display for WhereClause<'a> {
                 }
                 &clean::WherePredicate::RegionPredicate { ref lifetime, ref bounds } => {
                     clause.push_str(&format!("{}: {}",
-                                             lifetime,
-                                             bounds.iter()
-                                                   .map(|b| b.to_string())
-                                                   .collect::<Vec<_>>()
-                                                   .join(" + ")));
+                                                lifetime,
+                                                bounds.iter()
+                                                    .map(|b| b.to_string())
+                                                    .collect::<Vec<_>>()
+                                                    .join(" + ")));
                 }
                 &clean::WherePredicate::EqPredicate { ref lhs, ref rhs } => {
                     if f.alternate() {
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 849121a0e0d87..93916619b6260 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -1772,33 +1772,33 @@ fn print_entries(f: &mut fmt::Formatter<'_>, e: &FxHashSet<ItemEntry>, title: &s
 }
 
 impl fmt::Display for AllTypes {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f,
+fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    write!(f,
 "<h1 class='fqn'>\
-     <span class='out-of-band'>\
-         <span id='render-detail'>\
-             <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
-                 [<span class='inner'>&#x2212;</span>]\
-             </a>\
-         </span>
-     </span>
-     <span class='in-band'>List of all items</span>\
+    <span class='out-of-band'>\
+        <span id='render-detail'>\
+            <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
+                [<span class='inner'>&#x2212;</span>]\
+            </a>\
+        </span>
+    </span>
+    <span class='in-band'>List of all items</span>\
 </h1>")?;
-        print_entries(f, &self.structs, "Structs", "structs")?;
-        print_entries(f, &self.enums, "Enums", "enums")?;
-        print_entries(f, &self.unions, "Unions", "unions")?;
-        print_entries(f, &self.primitives, "Primitives", "primitives")?;
-        print_entries(f, &self.traits, "Traits", "traits")?;
-        print_entries(f, &self.macros, "Macros", "macros")?;
-        print_entries(f, &self.attributes, "Attribute Macros", "attributes")?;
-        print_entries(f, &self.derives, "Derive Macros", "derives")?;
-        print_entries(f, &self.functions, "Functions", "functions")?;
-        print_entries(f, &self.typedefs, "Typedefs", "typedefs")?;
-        print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases")?;
-        print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types")?;
-        print_entries(f, &self.statics, "Statics", "statics")?;
-        print_entries(f, &self.constants, "Constants", "constants")
-    }
+    print_entries(f, &self.structs, "Structs", "structs")?;
+    print_entries(f, &self.enums, "Enums", "enums")?;
+    print_entries(f, &self.unions, "Unions", "unions")?;
+    print_entries(f, &self.primitives, "Primitives", "primitives")?;
+    print_entries(f, &self.traits, "Traits", "traits")?;
+    print_entries(f, &self.macros, "Macros", "macros")?;
+    print_entries(f, &self.attributes, "Attribute Macros", "attributes")?;
+    print_entries(f, &self.derives, "Derive Macros", "derives")?;
+    print_entries(f, &self.functions, "Functions", "functions")?;
+    print_entries(f, &self.typedefs, "Typedefs", "typedefs")?;
+    print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases")?;
+    print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types")?;
+    print_entries(f, &self.statics, "Statics", "statics")?;
+    print_entries(f, &self.constants, "Constants", "constants")
+}
 }
 
 #[derive(Debug)]
@@ -1829,27 +1829,27 @@ impl<'a> Settings<'a> {
 }
 
 impl<'a> fmt::Display for Settings<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f,
+fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    write!(f,
 "<h1 class='fqn'>\
-     <span class='in-band'>Rustdoc settings</span>\
+    <span class='in-band'>Rustdoc settings</span>\
 </h1>\
 <div class='settings'>{}</div>\
 <script src='{}settings{}.js'></script>",
-               self.settings.iter()
-                            .map(|(id, text, enabled)| {
-                                format!("<div class='setting-line'>\
-                                             <label class='toggle'>\
-                                                <input type='checkbox' id='{}' {}>\
-                                                <span class='slider'></span>\
-                                             </label>\
-                                             <div>{}</div>\
-                                         </div>", id, if *enabled { " checked" } else { "" }, text)
-                            })
-                            .collect::<String>(),
-               self.root_path,
-               self.suffix)
-    }
+            self.settings.iter()
+                        .map(|(id, text, enabled)| {
+                            format!("<div class='setting-line'>\
+                                            <label class='toggle'>\
+                                            <input type='checkbox' id='{}' {}>\
+                                            <span class='slider'></span>\
+                                            </label>\
+                                            <div>{}</div>\
+                                        </div>", id, if *enabled { " checked" } else { "" }, text)
+                        })
+                        .collect::<String>(),
+            self.root_path,
+            self.suffix)
+}
 }
 
 impl Context {
@@ -2205,108 +2205,108 @@ where F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 impl<'a> fmt::Display for Item<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        debug_assert!(!self.item.is_stripped());
-        // Write the breadcrumb trail header for the top
-        write!(fmt, "<h1 class='fqn'><span class='out-of-band'>")?;
-        if let Some(version) = self.item.stable_since() {
-            write!(fmt, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
-                   version)?;
-        }
-        write!(fmt,
-               "<span id='render-detail'>\
-                   <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" \
-                      title=\"collapse all docs\">\
-                       [<span class='inner'>&#x2212;</span>]\
-                   </a>\
-               </span>")?;
-
-        // Write `src` tag
-        //
-        // When this item is part of a `pub use` in a downstream crate, the
-        // [src] link in the downstream documentation will actually come back to
-        // this page, and this link will be auto-clicked. The `id` attribute is
-        // used to find the link to auto-click.
-        if self.cx.shared.include_sources && !self.item.is_primitive() {
-            if let Some(l) = self.src_href() {
-                write!(fmt, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                       l, "goto source code")?;
-            }
-        }
-
-        write!(fmt, "</span>")?; // out-of-band
-        write!(fmt, "<span class='in-band'>")?;
-        match self.item.inner {
-            clean::ModuleItem(ref m) => if m.is_crate {
-                    write!(fmt, "Crate ")?;
-                } else {
-                    write!(fmt, "Module ")?;
-                },
-            clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => write!(fmt, "Function ")?,
-            clean::TraitItem(..) => write!(fmt, "Trait ")?,
-            clean::StructItem(..) => write!(fmt, "Struct ")?,
-            clean::UnionItem(..) => write!(fmt, "Union ")?,
-            clean::EnumItem(..) => write!(fmt, "Enum ")?,
-            clean::TypedefItem(..) => write!(fmt, "Type Definition ")?,
-            clean::MacroItem(..) => write!(fmt, "Macro ")?,
-            clean::ProcMacroItem(ref mac) => match mac.kind {
-                MacroKind::Bang => write!(fmt, "Macro ")?,
-                MacroKind::Attr => write!(fmt, "Attribute Macro ")?,
-                MacroKind::Derive => write!(fmt, "Derive Macro ")?,
-            }
-            clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
-            clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
-            clean::ConstantItem(..) => write!(fmt, "Constant ")?,
-            clean::ForeignTypeItem => write!(fmt, "Foreign Type ")?,
-            clean::KeywordItem(..) => write!(fmt, "Keyword ")?,
-            clean::OpaqueTyItem(..) => write!(fmt, "Opaque Type ")?,
-            clean::TraitAliasItem(..) => write!(fmt, "Trait Alias ")?,
-            _ => {
-                // We don't generate pages for any other type.
-                unreachable!();
-            }
-        }
-        if !self.item.is_primitive() && !self.item.is_keyword() {
-            let cur = &self.cx.current;
-            let amt = if self.item.is_mod() { cur.len() - 1 } else { cur.len() };
-            for (i, component) in cur.iter().enumerate().take(amt) {
-                write!(fmt, "<a href='{}index.html'>{}</a>::<wbr>",
-                       "../".repeat(cur.len() - i - 1),
-                       component)?;
-            }
-        }
-        write!(fmt, "<a class=\"{}\" href=''>{}</a>",
-               self.item.type_(), self.item.name.as_ref().unwrap())?;
-
-        write!(fmt, "</span></h1>")?; // in-band
-
-        match self.item.inner {
-            clean::ModuleItem(ref m) =>
-                item_module(fmt, self.cx, self.item, &m.items),
-            clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
-                item_function(fmt, self.cx, self.item, f),
-            clean::TraitItem(ref t) => item_trait(fmt, self.cx, self.item, t),
-            clean::StructItem(ref s) => item_struct(fmt, self.cx, self.item, s),
-            clean::UnionItem(ref s) => item_union(fmt, self.cx, self.item, s),
-            clean::EnumItem(ref e) => item_enum(fmt, self.cx, self.item, e),
-            clean::TypedefItem(ref t, _) => item_typedef(fmt, self.cx, self.item, t),
-            clean::MacroItem(ref m) => item_macro(fmt, self.cx, self.item, m),
-            clean::ProcMacroItem(ref m) => item_proc_macro(fmt, self.cx, self.item, m),
-            clean::PrimitiveItem(ref p) => item_primitive(fmt, self.cx, self.item, p),
-            clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
-                item_static(fmt, self.cx, self.item, i),
-            clean::ConstantItem(ref c) => item_constant(fmt, self.cx, self.item, c),
-            clean::ForeignTypeItem => item_foreign_type(fmt, self.cx, self.item),
-            clean::KeywordItem(ref k) => item_keyword(fmt, self.cx, self.item, k),
-            clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, self.cx, self.item, e),
-            clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, self.cx, self.item, ta),
-            _ => {
-                // We don't generate pages for any other type.
-                unreachable!();
-            }
+fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    debug_assert!(!self.item.is_stripped());
+    // Write the breadcrumb trail header for the top
+    write!(fmt, "<h1 class='fqn'><span class='out-of-band'>")?;
+    if let Some(version) = self.item.stable_since() {
+        write!(fmt, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
+                version)?;
+    }
+    write!(fmt,
+            "<span id='render-detail'>\
+                <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" \
+                    title=\"collapse all docs\">\
+                    [<span class='inner'>&#x2212;</span>]\
+                </a>\
+            </span>")?;
+
+    // Write `src` tag
+    //
+    // When this item is part of a `pub use` in a downstream crate, the
+    // [src] link in the downstream documentation will actually come back to
+    // this page, and this link will be auto-clicked. The `id` attribute is
+    // used to find the link to auto-click.
+    if self.cx.shared.include_sources && !self.item.is_primitive() {
+        if let Some(l) = self.src_href() {
+            write!(fmt, "<a class='srclink' href='{}' title='{}'>[src]</a>",
+                    l, "goto source code")?;
+        }
+    }
+
+    write!(fmt, "</span>")?; // out-of-band
+    write!(fmt, "<span class='in-band'>")?;
+    match self.item.inner {
+        clean::ModuleItem(ref m) => if m.is_crate {
+                write!(fmt, "Crate ")?;
+            } else {
+                write!(fmt, "Module ")?;
+            },
+        clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => write!(fmt, "Function ")?,
+        clean::TraitItem(..) => write!(fmt, "Trait ")?,
+        clean::StructItem(..) => write!(fmt, "Struct ")?,
+        clean::UnionItem(..) => write!(fmt, "Union ")?,
+        clean::EnumItem(..) => write!(fmt, "Enum ")?,
+        clean::TypedefItem(..) => write!(fmt, "Type Definition ")?,
+        clean::MacroItem(..) => write!(fmt, "Macro ")?,
+        clean::ProcMacroItem(ref mac) => match mac.kind {
+            MacroKind::Bang => write!(fmt, "Macro ")?,
+            MacroKind::Attr => write!(fmt, "Attribute Macro ")?,
+            MacroKind::Derive => write!(fmt, "Derive Macro ")?,
+        }
+        clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
+        clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
+        clean::ConstantItem(..) => write!(fmt, "Constant ")?,
+        clean::ForeignTypeItem => write!(fmt, "Foreign Type ")?,
+        clean::KeywordItem(..) => write!(fmt, "Keyword ")?,
+        clean::OpaqueTyItem(..) => write!(fmt, "Opaque Type ")?,
+        clean::TraitAliasItem(..) => write!(fmt, "Trait Alias ")?,
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
+        }
+    }
+    if !self.item.is_primitive() && !self.item.is_keyword() {
+        let cur = &self.cx.current;
+        let amt = if self.item.is_mod() { cur.len() - 1 } else { cur.len() };
+        for (i, component) in cur.iter().enumerate().take(amt) {
+            write!(fmt, "<a href='{}index.html'>{}</a>::<wbr>",
+                    "../".repeat(cur.len() - i - 1),
+                    component)?;
+        }
+    }
+    write!(fmt, "<a class=\"{}\" href=''>{}</a>",
+            self.item.type_(), self.item.name.as_ref().unwrap())?;
+
+    write!(fmt, "</span></h1>")?; // in-band
+
+    match self.item.inner {
+        clean::ModuleItem(ref m) =>
+            item_module(fmt, self.cx, self.item, &m.items),
+        clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
+            item_function(fmt, self.cx, self.item, f),
+        clean::TraitItem(ref t) => item_trait(fmt, self.cx, self.item, t),
+        clean::StructItem(ref s) => item_struct(fmt, self.cx, self.item, s),
+        clean::UnionItem(ref s) => item_union(fmt, self.cx, self.item, s),
+        clean::EnumItem(ref e) => item_enum(fmt, self.cx, self.item, e),
+        clean::TypedefItem(ref t, _) => item_typedef(fmt, self.cx, self.item, t),
+        clean::MacroItem(ref m) => item_macro(fmt, self.cx, self.item, m),
+        clean::ProcMacroItem(ref m) => item_proc_macro(fmt, self.cx, self.item, m),
+        clean::PrimitiveItem(ref p) => item_primitive(fmt, self.cx, self.item, p),
+        clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
+            item_static(fmt, self.cx, self.item, i),
+        clean::ConstantItem(ref c) => item_constant(fmt, self.cx, self.item, c),
+        clean::ForeignTypeItem => item_foreign_type(fmt, self.cx, self.item),
+        clean::KeywordItem(ref k) => item_keyword(fmt, self.cx, self.item, k),
+        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, self.cx, self.item, e),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, self.cx, self.item, ta),
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
         }
     }
 }
+}
 
 fn item_path(ty: ItemType, name: &str) -> String {
     match ty {
@@ -3834,9 +3834,9 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
         struct RendererStruct<'a, 'b, 'c>(&'a Context, Vec<&'b &'b Impl>, &'c clean::Item);
 
         impl<'a, 'b, 'c> fmt::Display for RendererStruct<'a, 'b, 'c> {
-            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-                render_impls(self.0, fmt, &self.1, self.2)
-            }
+        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+            render_impls(self.0, fmt, &self.1, self.2)
+        }
         }
 
         let impls = RendererStruct(cx, concrete, containing_item).to_string();
@@ -4264,97 +4264,97 @@ fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item)
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-    fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
-        let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
-
-        if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
-            || it.is_enum() || it.is_mod() || it.is_typedef() {
-            write!(buffer, "<p class='location'>{}{}</p>",
-                match it.inner {
-                    clean::StructItem(..) => "Struct ",
-                    clean::TraitItem(..) => "Trait ",
-                    clean::PrimitiveItem(..) => "Primitive Type ",
-                    clean::UnionItem(..) => "Union ",
-                    clean::EnumItem(..) => "Enum ",
-                    clean::TypedefItem(..) => "Type Definition ",
-                    clean::ForeignTypeItem => "Foreign Type ",
-                    clean::ModuleItem(..) => if it.is_crate() {
-                        "Crate "
-                    } else {
-                        "Module "
-                    },
-                    _ => "",
+fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer) {
+    let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
+
+    if it.is_struct() || it.is_trait() || it.is_primitive() || it.is_union()
+        || it.is_enum() || it.is_mod() || it.is_typedef() {
+        write!(buffer, "<p class='location'>{}{}</p>",
+            match it.inner {
+                clean::StructItem(..) => "Struct ",
+                clean::TraitItem(..) => "Trait ",
+                clean::PrimitiveItem(..) => "Primitive Type ",
+                clean::UnionItem(..) => "Union ",
+                clean::EnumItem(..) => "Enum ",
+                clean::TypedefItem(..) => "Type Definition ",
+                clean::ForeignTypeItem => "Foreign Type ",
+                clean::ModuleItem(..) => if it.is_crate() {
+                    "Crate "
+                } else {
+                    "Module "
                 },
-                it.name.as_ref().unwrap());
-        }
-
-        if it.is_crate() {
-            if let Some(ref version) = cache().crate_version {
-                write!(buffer,
-                       "<div class='block version'>\
-                        <p>Version {}</p>\
-                        </div>",
-                       version);
-            }
-        }
-
-        write!(buffer, "<div class=\"sidebar-elems\">");
-        if it.is_crate() {
-            write!(buffer, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
-                   it.name.as_ref().expect("crates always have a name"));
-        }
-        match it.inner {
-            clean::StructItem(ref s) => sidebar_struct(buffer, it, s),
-            clean::TraitItem(ref t) => sidebar_trait(buffer, it, t),
-            clean::PrimitiveItem(ref p) => sidebar_primitive(buffer, it, p),
-            clean::UnionItem(ref u) => sidebar_union(buffer, it, u),
-            clean::EnumItem(ref e) => sidebar_enum(buffer, it, e),
-            clean::TypedefItem(ref t, _) => sidebar_typedef(buffer, it, t),
-            clean::ModuleItem(ref m) => sidebar_module(buffer, it, &m.items),
-            clean::ForeignTypeItem => sidebar_foreign_type(buffer, it),
-            _ => (),
-        }
-
-        // The sidebar is designed to display sibling functions, modules and
-        // other miscellaneous information. since there are lots of sibling
-        // items (and that causes quadratic growth in large modules),
-        // we refactor common parts into a shared JavaScript file per module.
-        // still, we don't move everything into JS because we want to preserve
-        // as much HTML as possible in order to allow non-JS-enabled browsers
-        // to navigate the documentation (though slightly inefficiently).
-
-        write!(buffer, "<p class='location'>");
-        for (i, name) in cx.current.iter().take(parentlen).enumerate() {
-            if i > 0 {
-                write!(buffer, "::<wbr>");
-            }
-            write!(buffer, "<a href='{}index.html'>{}</a>",
-                   &cx.root_path()[..(cx.current.len() - i - 1) * 3],
-                   *name);
-        }
-        write!(buffer, "</p>");
-
-        // Sidebar refers to the enclosing module, not this module.
-        let relpath = if it.is_mod() { "../" } else { "" };
-        write!(buffer,
-               "<script>window.sidebarCurrent = {{\
-                   name: '{name}', \
-                   ty: '{ty}', \
-                   relpath: '{path}'\
-                }};</script>",
-               name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
-               ty = it.type_().css_class(),
-               path = relpath);
-        if parentlen == 0 {
-            // There is no sidebar-items.js beyond the crate root path
-            // FIXME maybe dynamic crate loading can be merged here
-        } else {
-            write!(buffer, "<script defer src=\"{path}sidebar-items.js\"></script>",
-                   path = relpath);
-        }
-        // Closes sidebar-elems div.
-        write!(buffer, "</div>");
+                _ => "",
+            },
+            it.name.as_ref().unwrap());
+    }
+
+    if it.is_crate() {
+        if let Some(ref version) = cache().crate_version {
+            write!(buffer,
+                    "<div class='block version'>\
+                    <p>Version {}</p>\
+                    </div>",
+                    version);
+        }
+    }
+
+    write!(buffer, "<div class=\"sidebar-elems\">");
+    if it.is_crate() {
+        write!(buffer, "<a id='all-types' href='all.html'><p>See all {}'s items</p></a>",
+                it.name.as_ref().expect("crates always have a name"));
+    }
+    match it.inner {
+        clean::StructItem(ref s) => sidebar_struct(buffer, it, s),
+        clean::TraitItem(ref t) => sidebar_trait(buffer, it, t),
+        clean::PrimitiveItem(ref p) => sidebar_primitive(buffer, it, p),
+        clean::UnionItem(ref u) => sidebar_union(buffer, it, u),
+        clean::EnumItem(ref e) => sidebar_enum(buffer, it, e),
+        clean::TypedefItem(ref t, _) => sidebar_typedef(buffer, it, t),
+        clean::ModuleItem(ref m) => sidebar_module(buffer, it, &m.items),
+        clean::ForeignTypeItem => sidebar_foreign_type(buffer, it),
+        _ => (),
+    }
+
+    // The sidebar is designed to display sibling functions, modules and
+    // other miscellaneous information. since there are lots of sibling
+    // items (and that causes quadratic growth in large modules),
+    // we refactor common parts into a shared JavaScript file per module.
+    // still, we don't move everything into JS because we want to preserve
+    // as much HTML as possible in order to allow non-JS-enabled browsers
+    // to navigate the documentation (though slightly inefficiently).
+
+    write!(buffer, "<p class='location'>");
+    for (i, name) in cx.current.iter().take(parentlen).enumerate() {
+        if i > 0 {
+            write!(buffer, "::<wbr>");
+        }
+        write!(buffer, "<a href='{}index.html'>{}</a>",
+                &cx.root_path()[..(cx.current.len() - i - 1) * 3],
+                *name);
+    }
+    write!(buffer, "</p>");
+
+    // Sidebar refers to the enclosing module, not this module.
+    let relpath = if it.is_mod() { "../" } else { "" };
+    write!(buffer,
+            "<script>window.sidebarCurrent = {{\
+                name: '{name}', \
+                ty: '{ty}', \
+                relpath: '{path}'\
+            }};</script>",
+            name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
+            ty = it.type_().css_class(),
+            path = relpath);
+    if parentlen == 0 {
+        // There is no sidebar-items.js beyond the crate root path
+        // FIXME maybe dynamic crate loading can be merged here
+    } else {
+        write!(buffer, "<script defer src=\"{path}sidebar-items.js\"></script>",
+                path = relpath);
     }
+    // Closes sidebar-elems div.
+    write!(buffer, "</div>");
+}
 
 fn get_next_url(used_links: &mut FxHashSet<String>, url: String) -> String {
     if used_links.insert(url.clone()) {
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index 94ae14226097f..6dccfdadf0fb8 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -160,22 +160,22 @@ where
 struct Source<'a>(&'a str);
 
 impl<'a> fmt::Display for Source<'a> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let Source(s) = *self;
-        let lines = s.lines().count();
-        let mut cols = 0;
-        let mut tmp = lines;
-        while tmp > 0 {
-            cols += 1;
-            tmp /= 10;
-        }
-        write!(fmt, "<pre class=\"line-numbers\">")?;
-        for i in 1..=lines {
-            write!(fmt, "<span id=\"{0}\">{0:1$}</span>\n", i, cols)?;
-        }
-        write!(fmt, "</pre>")?;
-        write!(fmt, "{}",
-               highlight::render_with_highlighting(s, None, None, None))?;
-        Ok(())
+fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+    let Source(s) = *self;
+    let lines = s.lines().count();
+    let mut cols = 0;
+    let mut tmp = lines;
+    while tmp > 0 {
+        cols += 1;
+        tmp /= 10;
     }
+    write!(fmt, "<pre class=\"line-numbers\">")?;
+    for i in 1..=lines {
+        write!(fmt, "<span id=\"{0}\">{0:1$}</span>\n", i, cols)?;
+    }
+    write!(fmt, "</pre>")?;
+    write!(fmt, "{}",
+            highlight::render_with_highlighting(s, None, None, None))?;
+    Ok(())
+}
 }

From 61653133e845a60ebc5aceb7036c71a6c75d251c Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 12:18:25 -0400
Subject: [PATCH 27/33] layout::render takes Print instead of fmt::Display

---
 src/librustdoc/html/format.rs  |  6 +++++-
 src/librustdoc/html/layout.rs  |  7 +++----
 src/librustdoc/html/render.rs  | 10 +++++-----
 src/librustdoc/html/sources.rs |  3 ++-
 4 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index f3c40c8568bb6..80f34fb17d2e8 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -99,7 +99,11 @@ impl Buffer {
         self.into_inner()
     }
 
-    crate fn display<T: fmt::Display>(&mut self, t: T) {
+    crate fn with_formatter<T: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result>(&mut self, t: T) {
+        self.from_display(display_fn(move |f| (t)(f)));
+    }
+
+    crate fn from_display<T: std::fmt::Display>(&mut self, t: T) {
         if self.for_html {
             write!(self, "{}", t);
         } else {
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index 1202f411f912c..56074f4ab1192 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -1,4 +1,3 @@
-use std::fmt;
 use std::path::PathBuf;
 
 use crate::externalfiles::ExternalHtml;
@@ -31,11 +30,11 @@ pub struct Page<'a> {
     pub static_extra_scripts: &'a [&'a str],
 }
 
-pub fn render<T: fmt::Display, S: Print>(
+pub fn render<T: Print, S: Print>(
     layout: &Layout,
     page: &Page<'_>,
     sidebar: S,
-    t: &T,
+    t: T,
     themes: &[PathBuf],
 ) -> String {
     let static_root_path = page.static_root_path.unwrap_or(page.root_path);
@@ -175,7 +174,7 @@ pub fn render<T: fmt::Display, S: Print>(
     } else {
         String::new()
     },
-    content   = *t,
+    content   = Buffer::html().to_display(t),
     static_root_path = static_root_path,
     root_path = page.root_path,
     css_class = page.css_class,
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 93916619b6260..fc4f0a3cb48c1 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -65,7 +65,7 @@ use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::fold::DocFolder;
 use crate::html::escape::Escape;
-use crate::html::format::{Print, Buffer, AsyncSpace, ConstnessSpace};
+use crate::html::format::{Buffer, AsyncSpace, ConstnessSpace};
 use crate::html::format::{GenericBounds, WhereClause, href, AbiSpace, DefaultSpace};
 use crate::html::format::{VisSpace, Function, UnsafetySpace, MutableSpace};
 use crate::html::format::fmt_impl_for_trait_page;
@@ -1172,7 +1172,7 @@ themePicker.onblur = handleThemeButtonsBlur;
                                     })
                                     .collect::<String>());
             let v = layout::render(&cx.shared.layout,
-                           &page, "", &content,
+                           &page, "", content,
                            &cx.shared.themes);
             cx.shared.fs.write(&dst, v.as_bytes())?;
         }
@@ -1919,7 +1919,7 @@ impl Context {
             String::new()
         };
         let v = layout::render(&self.shared.layout,
-                       &page, sidebar, &all,
+                       &page, sidebar, |buf: &mut Buffer| buf.from_display(all),
                        &self.shared.themes);
         self.shared.fs.write(&final_file, v.as_bytes())?;
 
@@ -1935,7 +1935,7 @@ impl Context {
         themes.push(PathBuf::from("settings.css"));
         let v = layout::render(
             &self.shared.layout,
-            &page, sidebar, &settings,
+            &page, sidebar, |buf: &mut Buffer| buf.from_display(settings),
             &themes);
         self.shared.fs.write(&settings_file, v.as_bytes())?;
 
@@ -1993,7 +1993,7 @@ impl Context {
         if !self.render_redirect_pages {
             layout::render(&self.shared.layout, &page,
                            |buf: &mut _| print_sidebar(self, it, buf),
-                           &Item{ cx: self, item: it },
+                           |buf: &mut Buffer| buf.from_display(Item { cx: self, item: it }),
                            &self.shared.themes)
         } else {
             let mut url = self.root_path();
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index 6dccfdadf0fb8..e94ae1d968ef5 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -4,6 +4,7 @@ use crate::fold::DocFolder;
 use crate::html::layout;
 use crate::html::render::{Error, SharedContext, BASIC_KEYWORDS};
 use crate::html::highlight;
+use crate::html::format::Buffer;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::{Component, Path, PathBuf};
@@ -120,7 +121,7 @@ impl<'a> SourceCollector<'a> {
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
         let v = layout::render(&self.scx.layout,
-                       &page, "", &Source(contents),
+                       &page, "", |buf: &mut Buffer| buf.from_display(Source(&contents)),
                        &self.scx.themes);
         self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);

From a57f00d7e19a072cacfa763af22999a8ac297826 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 12:20:56 -0400
Subject: [PATCH 28/33] Move Source to Buffer

---
 src/librustdoc/html/sources.rs | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
index e94ae1d968ef5..d840683a7af87 100644
--- a/src/librustdoc/html/sources.rs
+++ b/src/librustdoc/html/sources.rs
@@ -8,7 +8,6 @@ use crate::html::format::Buffer;
 use std::ffi::OsStr;
 use std::fs;
 use std::path::{Component, Path, PathBuf};
-use std::fmt;
 use syntax::source_map::FileName;
 
 crate fn render(dst: &Path, scx: &mut SharedContext,
@@ -121,7 +120,7 @@ impl<'a> SourceCollector<'a> {
             static_extra_scripts: &[&format!("source-script{}", self.scx.resource_suffix)],
         };
         let v = layout::render(&self.scx.layout,
-                       &page, "", |buf: &mut Buffer| buf.from_display(Source(&contents)),
+                       &page, "", |buf: &mut _| print_src(buf, &contents),
                        &self.scx.themes);
         self.scx.fs.write(&cur, v.as_bytes())?;
         self.scx.local_sources.insert(p.clone(), href);
@@ -158,11 +157,7 @@ where
 
 /// Wrapper struct to render the source code of a file. This will do things like
 /// adding line numbers to the left-hand side.
-struct Source<'a>(&'a str);
-
-impl<'a> fmt::Display for Source<'a> {
-fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-    let Source(s) = *self;
+fn print_src(buf: &mut Buffer, s: &str) {
     let lines = s.lines().count();
     let mut cols = 0;
     let mut tmp = lines;
@@ -170,13 +165,11 @@ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         cols += 1;
         tmp /= 10;
     }
-    write!(fmt, "<pre class=\"line-numbers\">")?;
+    write!(buf, "<pre class=\"line-numbers\">");
     for i in 1..=lines {
-        write!(fmt, "<span id=\"{0}\">{0:1$}</span>\n", i, cols)?;
+        write!(buf, "<span id=\"{0}\">{0:1$}</span>\n", i, cols);
     }
-    write!(fmt, "</pre>")?;
-    write!(fmt, "{}",
-            highlight::render_with_highlighting(s, None, None, None))?;
-    Ok(())
-}
+    write!(buf, "</pre>");
+    write!(buf, "{}",
+            highlight::render_with_highlighting(s, None, None, None));
 }

From cd92ed27f83373cb63617adfb50df3e4cfa729c6 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 12:27:27 -0400
Subject: [PATCH 29/33] Settings to function

---
 src/librustdoc/html/render.rs | 55 ++++++++++++-----------------------
 1 file changed, 19 insertions(+), 36 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index fc4f0a3cb48c1..ee6441366f6b6 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -1801,42 +1801,25 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 }
 
-#[derive(Debug)]
-struct Settings<'a> {
+fn settings(root_path: &str, suffix: &str) -> String {
     // (id, explanation, default value)
-    settings: Vec<(&'static str, &'static str, bool)>,
-    root_path: &'a str,
-    suffix: &'a str,
-}
-
-impl<'a> Settings<'a> {
-    pub fn new(root_path: &'a str, suffix: &'a str) -> Settings<'a> {
-        Settings {
-            settings: vec![
-                ("item-declarations", "Auto-hide item declarations.", true),
-                ("item-attributes", "Auto-hide item attributes.", true),
-                ("trait-implementations", "Auto-hide trait implementations documentation",
-                 true),
-                ("method-docs", "Auto-hide item methods' documentation", false),
-                ("go-to-only-result", "Directly go to item in search if there is only one result",
-                 false),
-                ("line-numbers", "Show line numbers on code examples", false),
-            ],
-            root_path,
-            suffix,
-        }
-    }
-}
-
-impl<'a> fmt::Display for Settings<'a> {
-fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(f,
+    let settings = [
+        ("item-declarations", "Auto-hide item declarations.", true),
+        ("item-attributes", "Auto-hide item attributes.", true),
+        ("trait-implementations", "Auto-hide trait implementations documentation",
+            true),
+        ("method-docs", "Auto-hide item methods' documentation", false),
+        ("go-to-only-result", "Directly go to item in search if there is only one result",
+            false),
+        ("line-numbers", "Show line numbers on code examples", false),
+    ];
+    format!(
 "<h1 class='fqn'>\
     <span class='in-band'>Rustdoc settings</span>\
 </h1>\
 <div class='settings'>{}</div>\
 <script src='{}settings{}.js'></script>",
-            self.settings.iter()
+            settings.iter()
                         .map(|(id, text, enabled)| {
                             format!("<div class='setting-line'>\
                                             <label class='toggle'>\
@@ -1847,9 +1830,8 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                                         </div>", id, if *enabled { " checked" } else { "" }, text)
                         })
                         .collect::<String>(),
-            self.root_path,
-            self.suffix)
-}
+            root_path,
+            suffix)
 }
 
 impl Context {
@@ -1924,8 +1906,6 @@ impl Context {
         self.shared.fs.write(&final_file, v.as_bytes())?;
 
         // Generating settings page.
-        let settings = Settings::new(self.shared.static_root_path.as_deref().unwrap_or("./"),
-                                     &self.shared.resource_suffix);
         page.title = "Rustdoc settings";
         page.description = "Settings of Rustdoc";
         page.root_path = "./";
@@ -1935,7 +1915,10 @@ impl Context {
         themes.push(PathBuf::from("settings.css"));
         let v = layout::render(
             &self.shared.layout,
-            &page, sidebar, |buf: &mut Buffer| buf.from_display(settings),
+            &page, sidebar, settings(
+                self.shared.static_root_path.as_deref().unwrap_or("./"),
+                &self.shared.resource_suffix
+            ),
             &themes);
         self.shared.fs.write(&settings_file, v.as_bytes())?;
 

From b2eb65ba5621a405224eb2502c62818d9d5a44de Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 12:31:55 -0400
Subject: [PATCH 30/33] AllTypes to function

---
 src/librustdoc/html/render.rs | 62 +++++++++++++++++------------------
 1 file changed, 30 insertions(+), 32 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index ee6441366f6b6..998f42118c2f1 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -1757,8 +1757,7 @@ impl AllTypes {
     }
 }
 
-fn print_entries(f: &mut fmt::Formatter<'_>, e: &FxHashSet<ItemEntry>, title: &str,
-                 class: &str) -> fmt::Result {
+fn print_entries(f: &mut Buffer, e: &FxHashSet<ItemEntry>, title: &str, class: &str) {
     if !e.is_empty() {
         let mut e: Vec<&ItemEntry> = e.iter().collect();
         e.sort();
@@ -1766,39 +1765,38 @@ fn print_entries(f: &mut fmt::Formatter<'_>, e: &FxHashSet<ItemEntry>, title: &s
                title,
                Escape(title),
                class,
-               e.iter().map(|s| format!("<li>{}</li>", s)).collect::<String>())?;
+               e.iter().map(|s| format!("<li>{}</li>", s)).collect::<String>());
     }
-    Ok(())
 }
 
-impl fmt::Display for AllTypes {
-fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(f,
-"<h1 class='fqn'>\
-    <span class='out-of-band'>\
-        <span id='render-detail'>\
-            <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
-                [<span class='inner'>&#x2212;</span>]\
-            </a>\
+impl AllTypes {
+    fn print(self, f: &mut Buffer) {
+        write!(f,
+    "<h1 class='fqn'>\
+        <span class='out-of-band'>\
+            <span id='render-detail'>\
+                <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" title=\"collapse all docs\">\
+                    [<span class='inner'>&#x2212;</span>]\
+                </a>\
+            </span>
         </span>
-    </span>
-    <span class='in-band'>List of all items</span>\
-</h1>")?;
-    print_entries(f, &self.structs, "Structs", "structs")?;
-    print_entries(f, &self.enums, "Enums", "enums")?;
-    print_entries(f, &self.unions, "Unions", "unions")?;
-    print_entries(f, &self.primitives, "Primitives", "primitives")?;
-    print_entries(f, &self.traits, "Traits", "traits")?;
-    print_entries(f, &self.macros, "Macros", "macros")?;
-    print_entries(f, &self.attributes, "Attribute Macros", "attributes")?;
-    print_entries(f, &self.derives, "Derive Macros", "derives")?;
-    print_entries(f, &self.functions, "Functions", "functions")?;
-    print_entries(f, &self.typedefs, "Typedefs", "typedefs")?;
-    print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases")?;
-    print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types")?;
-    print_entries(f, &self.statics, "Statics", "statics")?;
-    print_entries(f, &self.constants, "Constants", "constants")
-}
+        <span class='in-band'>List of all items</span>\
+    </h1>");
+        print_entries(f, &self.structs, "Structs", "structs");
+        print_entries(f, &self.enums, "Enums", "enums");
+        print_entries(f, &self.unions, "Unions", "unions");
+        print_entries(f, &self.primitives, "Primitives", "primitives");
+        print_entries(f, &self.traits, "Traits", "traits");
+        print_entries(f, &self.macros, "Macros", "macros");
+        print_entries(f, &self.attributes, "Attribute Macros", "attributes");
+        print_entries(f, &self.derives, "Derive Macros", "derives");
+        print_entries(f, &self.functions, "Functions", "functions");
+        print_entries(f, &self.typedefs, "Typedefs", "typedefs");
+        print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases");
+        print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types");
+        print_entries(f, &self.statics, "Statics", "statics");
+        print_entries(f, &self.constants, "Constants", "constants")
+    }
 }
 
 fn settings(root_path: &str, suffix: &str) -> String {
@@ -1901,7 +1899,7 @@ impl Context {
             String::new()
         };
         let v = layout::render(&self.shared.layout,
-                       &page, sidebar, |buf: &mut Buffer| buf.from_display(all),
+                       &page, sidebar, |buf: &mut Buffer| all.print(buf),
                        &self.shared.themes);
         self.shared.fs.write(&final_file, v.as_bytes())?;
 

From 31391ca0655af91e6b763b9e539b803b5df79e29 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 13:29:31 -0400
Subject: [PATCH 31/33] Item to function

---
 src/librustdoc/html/render.rs | 163 ++++++++++++++++------------------
 1 file changed, 79 insertions(+), 84 deletions(-)

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 998f42118c2f1..3bb9c42bb0db3 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -381,12 +381,6 @@ pub struct RenderInfo {
 // Helper structs for rendering items/sidebars and carrying along contextual
 // information
 
-#[derive(Copy, Clone)]
-struct Item<'a> {
-    cx: &'a Context,
-    item: &'a clean::Item,
-}
-
 /// Struct representing one entry in the JS search index. These are all emitted
 /// by hand to a large JS file at the end of cache-creation.
 #[derive(Debug)]
@@ -1974,7 +1968,7 @@ impl Context {
         if !self.render_redirect_pages {
             layout::render(&self.shared.layout, &page,
                            |buf: &mut _| print_sidebar(self, it, buf),
-                           |buf: &mut Buffer| buf.from_display(Item { cx: self, item: it }),
+                           |buf: &mut _| print_item(self, it, buf),
                            &self.shared.themes)
         } else {
             let mut url = self.root_path();
@@ -2115,7 +2109,7 @@ impl Context {
     }
 }
 
-impl<'a> Item<'a> {
+impl Context {
     /// Generates a url appropriate for an `href` attribute back to the source of
     /// this item.
     ///
@@ -2125,26 +2119,26 @@ impl<'a> Item<'a> {
     /// If `None` is returned, then a source link couldn't be generated. This
     /// may happen, for example, with externally inlined items where the source
     /// of their crate documentation isn't known.
-    fn src_href(&self) -> Option<String> {
-        let mut root = self.cx.root_path();
+    fn src_href(&self, item: &clean::Item) -> Option<String> {
+        let mut root = self.root_path();
 
         let cache = cache();
         let mut path = String::new();
 
         // We can safely ignore macros from other libraries
-        let file = match self.item.source.filename {
+        let file = match item.source.filename {
             FileName::Real(ref path) => path,
             _ => return None,
         };
 
-        let (krate, path) = if self.item.def_id.is_local() {
-            if let Some(path) = self.cx.shared.local_sources.get(file) {
-                (&self.cx.shared.layout.krate, path)
+        let (krate, path) = if item.def_id.is_local() {
+            if let Some(path) = self.shared.local_sources.get(file) {
+                (&self.shared.layout.krate, path)
             } else {
                 return None;
             }
         } else {
-            let (krate, src_root) = match *cache.extern_locations.get(&self.item.def_id.krate)? {
+            let (krate, src_root) = match *cache.extern_locations.get(&item.def_id.krate)? {
                 (ref name, ref src, Local) => (name, src),
                 (ref name, ref src, Remote(ref s)) => {
                     root = s.to_string();
@@ -2164,10 +2158,10 @@ impl<'a> Item<'a> {
             (krate, &path)
         };
 
-        let lines = if self.item.source.loline == self.item.source.hiline {
-            self.item.source.loline.to_string()
+        let lines = if item.source.loline == item.source.hiline {
+            item.source.loline.to_string()
         } else {
-            format!("{}-{}", self.item.source.loline, self.item.source.hiline)
+            format!("{}-{}", item.source.loline, item.source.hiline)
         };
         Some(format!("{root}src/{krate}/{path}#{lines}",
                      root = Escape(&root),
@@ -2185,22 +2179,21 @@ where F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result {
     write!(w, "</div>")
 }
 
-impl<'a> fmt::Display for Item<'a> {
-fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-    debug_assert!(!self.item.is_stripped());
+fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
+    debug_assert!(!item.is_stripped());
     // Write the breadcrumb trail header for the top
-    write!(fmt, "<h1 class='fqn'><span class='out-of-band'>")?;
-    if let Some(version) = self.item.stable_since() {
-        write!(fmt, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
-                version)?;
+    write!(buf, "<h1 class='fqn'><span class='out-of-band'>");
+    if let Some(version) = item.stable_since() {
+        write!(buf, "<span class='since' title='Stable since Rust version {0}'>{0}</span>",
+                version);
     }
-    write!(fmt,
+    write!(buf,
             "<span id='render-detail'>\
                 <a id=\"toggle-all-docs\" href=\"javascript:void(0)\" \
                     title=\"collapse all docs\">\
                     [<span class='inner'>&#x2212;</span>]\
                 </a>\
-            </span>")?;
+            </span>");
 
     // Write `src` tag
     //
@@ -2208,85 +2201,87 @@ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     // [src] link in the downstream documentation will actually come back to
     // this page, and this link will be auto-clicked. The `id` attribute is
     // used to find the link to auto-click.
-    if self.cx.shared.include_sources && !self.item.is_primitive() {
-        if let Some(l) = self.src_href() {
-            write!(fmt, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                    l, "goto source code")?;
+    if cx.shared.include_sources && !item.is_primitive() {
+        if let Some(l) = cx.src_href(item) {
+            write!(buf, "<a class='srclink' href='{}' title='{}'>[src]</a>",
+                    l, "goto source code");
         }
     }
 
-    write!(fmt, "</span>")?; // out-of-band
-    write!(fmt, "<span class='in-band'>")?;
-    match self.item.inner {
+    write!(buf, "</span>"); // out-of-band
+    write!(buf, "<span class='in-band'>");
+    let name = match item.inner {
         clean::ModuleItem(ref m) => if m.is_crate {
-                write!(fmt, "Crate ")?;
+                "Crate "
             } else {
-                write!(fmt, "Module ")?;
+                "Module "
             },
-        clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => write!(fmt, "Function ")?,
-        clean::TraitItem(..) => write!(fmt, "Trait ")?,
-        clean::StructItem(..) => write!(fmt, "Struct ")?,
-        clean::UnionItem(..) => write!(fmt, "Union ")?,
-        clean::EnumItem(..) => write!(fmt, "Enum ")?,
-        clean::TypedefItem(..) => write!(fmt, "Type Definition ")?,
-        clean::MacroItem(..) => write!(fmt, "Macro ")?,
+        clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => "Function ",
+        clean::TraitItem(..) => "Trait ",
+        clean::StructItem(..) => "Struct ",
+        clean::UnionItem(..) => "Union ",
+        clean::EnumItem(..) => "Enum ",
+        clean::TypedefItem(..) => "Type Definition ",
+        clean::MacroItem(..) => "Macro ",
         clean::ProcMacroItem(ref mac) => match mac.kind {
-            MacroKind::Bang => write!(fmt, "Macro ")?,
-            MacroKind::Attr => write!(fmt, "Attribute Macro ")?,
-            MacroKind::Derive => write!(fmt, "Derive Macro ")?,
-        }
-        clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
-        clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
-        clean::ConstantItem(..) => write!(fmt, "Constant ")?,
-        clean::ForeignTypeItem => write!(fmt, "Foreign Type ")?,
-        clean::KeywordItem(..) => write!(fmt, "Keyword ")?,
-        clean::OpaqueTyItem(..) => write!(fmt, "Opaque Type ")?,
-        clean::TraitAliasItem(..) => write!(fmt, "Trait Alias ")?,
+            MacroKind::Bang => "Macro ",
+            MacroKind::Attr => "Attribute Macro ",
+            MacroKind::Derive => "Derive Macro ",
+        }
+        clean::PrimitiveItem(..) => "Primitive Type ",
+        clean::StaticItem(..) | clean::ForeignStaticItem(..) => "Static ",
+        clean::ConstantItem(..) => "Constant ",
+        clean::ForeignTypeItem => "Foreign Type ",
+        clean::KeywordItem(..) => "Keyword ",
+        clean::OpaqueTyItem(..) => "Opaque Type ",
+        clean::TraitAliasItem(..) => "Trait Alias ",
         _ => {
             // We don't generate pages for any other type.
             unreachable!();
         }
-    }
-    if !self.item.is_primitive() && !self.item.is_keyword() {
-        let cur = &self.cx.current;
-        let amt = if self.item.is_mod() { cur.len() - 1 } else { cur.len() };
+    };
+    buf.write_str(name);
+    if !item.is_primitive() && !item.is_keyword() {
+        let cur = &cx.current;
+        let amt = if item.is_mod() { cur.len() - 1 } else { cur.len() };
         for (i, component) in cur.iter().enumerate().take(amt) {
-            write!(fmt, "<a href='{}index.html'>{}</a>::<wbr>",
+            write!(buf, "<a href='{}index.html'>{}</a>::<wbr>",
                     "../".repeat(cur.len() - i - 1),
-                    component)?;
+                    component);
         }
     }
-    write!(fmt, "<a class=\"{}\" href=''>{}</a>",
-            self.item.type_(), self.item.name.as_ref().unwrap())?;
+    write!(buf, "<a class=\"{}\" href=''>{}</a>",
+            item.type_(), item.name.as_ref().unwrap());
 
-    write!(fmt, "</span></h1>")?; // in-band
+    write!(buf, "</span></h1>"); // in-band
 
-    match self.item.inner {
+    buf.with_formatter(|fmt| {
+    match item.inner {
         clean::ModuleItem(ref m) =>
-            item_module(fmt, self.cx, self.item, &m.items),
+            item_module(fmt, cx, item, &m.items),
         clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
-            item_function(fmt, self.cx, self.item, f),
-        clean::TraitItem(ref t) => item_trait(fmt, self.cx, self.item, t),
-        clean::StructItem(ref s) => item_struct(fmt, self.cx, self.item, s),
-        clean::UnionItem(ref s) => item_union(fmt, self.cx, self.item, s),
-        clean::EnumItem(ref e) => item_enum(fmt, self.cx, self.item, e),
-        clean::TypedefItem(ref t, _) => item_typedef(fmt, self.cx, self.item, t),
-        clean::MacroItem(ref m) => item_macro(fmt, self.cx, self.item, m),
-        clean::ProcMacroItem(ref m) => item_proc_macro(fmt, self.cx, self.item, m),
-        clean::PrimitiveItem(ref p) => item_primitive(fmt, self.cx, self.item, p),
+            item_function(fmt, cx, item, f),
+        clean::TraitItem(ref t) => item_trait(fmt, cx, item, t),
+        clean::StructItem(ref s) => item_struct(fmt, cx, item, s),
+        clean::UnionItem(ref s) => item_union(fmt, cx, item, s),
+        clean::EnumItem(ref e) => item_enum(fmt, cx, item, e),
+        clean::TypedefItem(ref t, _) => item_typedef(fmt, cx, item, t),
+        clean::MacroItem(ref m) => item_macro(fmt, cx, item, m),
+        clean::ProcMacroItem(ref m) => item_proc_macro(fmt, cx, item, m),
+        clean::PrimitiveItem(ref p) => item_primitive(fmt, cx, item, p),
         clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
-            item_static(fmt, self.cx, self.item, i),
-        clean::ConstantItem(ref c) => item_constant(fmt, self.cx, self.item, c),
-        clean::ForeignTypeItem => item_foreign_type(fmt, self.cx, self.item),
-        clean::KeywordItem(ref k) => item_keyword(fmt, self.cx, self.item, k),
-        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, self.cx, self.item, e),
-        clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, self.cx, self.item, ta),
+            item_static(fmt, cx, item, i),
+        clean::ConstantItem(ref c) => item_constant(fmt, cx, item, c),
+        clean::ForeignTypeItem => item_foreign_type(fmt, cx, item),
+        clean::KeywordItem(ref k) => item_keyword(fmt, cx, item, k),
+        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, cx, item, e),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, cx, item, ta),
         _ => {
             // We don't generate pages for any other type.
             unreachable!();
         }
     }
-}
+    })
 }
 
 fn item_path(ty: ItemType, name: &str) -> String {
@@ -4004,7 +3999,7 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
         write!(w, "<a href='#{}' class='anchor'></a>", id)?;
         let since = i.impl_item.stability.as_ref().map(|s| &s.since[..]);
         render_stability_since_raw(w, since, outer_version)?;
-        if let Some(l) = (Item { item: &i.impl_item, cx: cx }).src_href() {
+        if let Some(l) = cx.src_href(&i.impl_item) {
             write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
                    l, "goto source code")?;
         }
@@ -4050,7 +4045,7 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                     render_assoc_item(w, item, link.anchor(&id), ItemType::Impl)?;
                     write!(w, "</code>")?;
                     render_stability_since_raw(w, item.stable_since(), outer_version)?;
-                    if let Some(l) = (Item { cx, item }).src_href() {
+                    if let Some(l) = cx.src_href(item) {
                         write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
                                l, "goto source code")?;
                     }
@@ -4073,7 +4068,7 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                 assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "")?;
                 write!(w, "</code>")?;
                 render_stability_since_raw(w, item.stable_since(), outer_version)?;
-                if let Some(l) = (Item { cx, item }).src_href() {
+                if let Some(l) = cx.src_href(item) {
                     write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
                             l, "goto source code")?;
                 }

From a9c6ef65ae8147396e58426897fc534bd42e6b2e Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 31 Aug 2019 15:47:55 -0400
Subject: [PATCH 32/33] Move to buffers throughout print_item

---
 src/librustdoc/html/format.rs |   6 +-
 src/librustdoc/html/render.rs | 791 ++++++++++++++++------------------
 2 files changed, 372 insertions(+), 425 deletions(-)

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 80f34fb17d2e8..dcd32192ff384 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -872,9 +872,9 @@ impl fmt::Display for clean::Impl {
 
 // The difference from above is that trait is not hyperlinked.
 pub fn fmt_impl_for_trait_page(i: &clean::Impl,
-                               f: &mut fmt::Formatter<'_>,
-                               use_absolute: bool) -> fmt::Result {
-    fmt_impl(i, f, false, use_absolute)
+                               f: &mut Buffer,
+                               use_absolute: bool) {
+    f.with_formatter(|f| fmt_impl(i, f, false, use_absolute))
 }
 
 impl fmt::Display for clean::Arguments {
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 3bb9c42bb0db3..b6b5b70e99fd5 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -2171,11 +2171,11 @@ impl Context {
     }
 }
 
-fn wrap_into_docblock<F>(w: &mut fmt::Formatter<'_>,
-                         f: F) -> fmt::Result
-where F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(w, "<div class=\"docblock type-decl hidden-by-usual-hider\">")?;
-    f(w)?;
+fn wrap_into_docblock<F>(w: &mut Buffer, f: F)
+    where F: FnOnce(&mut Buffer)
+{
+    write!(w, "<div class=\"docblock type-decl hidden-by-usual-hider\">");
+    f(w);
     write!(w, "</div>")
 }
 
@@ -2255,33 +2255,31 @@ fn print_item(cx: &Context, item: &clean::Item, buf: &mut Buffer) {
 
     write!(buf, "</span></h1>"); // in-band
 
-    buf.with_formatter(|fmt| {
     match item.inner {
         clean::ModuleItem(ref m) =>
-            item_module(fmt, cx, item, &m.items),
+            item_module(buf, cx, item, &m.items),
         clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) =>
-            item_function(fmt, cx, item, f),
-        clean::TraitItem(ref t) => item_trait(fmt, cx, item, t),
-        clean::StructItem(ref s) => item_struct(fmt, cx, item, s),
-        clean::UnionItem(ref s) => item_union(fmt, cx, item, s),
-        clean::EnumItem(ref e) => item_enum(fmt, cx, item, e),
-        clean::TypedefItem(ref t, _) => item_typedef(fmt, cx, item, t),
-        clean::MacroItem(ref m) => item_macro(fmt, cx, item, m),
-        clean::ProcMacroItem(ref m) => item_proc_macro(fmt, cx, item, m),
-        clean::PrimitiveItem(ref p) => item_primitive(fmt, cx, item, p),
+            item_function(buf, cx, item, f),
+        clean::TraitItem(ref t) => item_trait(buf, cx, item, t),
+        clean::StructItem(ref s) => item_struct(buf, cx, item, s),
+        clean::UnionItem(ref s) => item_union(buf, cx, item, s),
+        clean::EnumItem(ref e) => item_enum(buf, cx, item, e),
+        clean::TypedefItem(ref t, _) => item_typedef(buf, cx, item, t),
+        clean::MacroItem(ref m) => item_macro(buf, cx, item, m),
+        clean::ProcMacroItem(ref m) => item_proc_macro(buf, cx, item, m),
+        clean::PrimitiveItem(ref p) => item_primitive(buf, cx, item, p),
         clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) =>
-            item_static(fmt, cx, item, i),
-        clean::ConstantItem(ref c) => item_constant(fmt, cx, item, c),
-        clean::ForeignTypeItem => item_foreign_type(fmt, cx, item),
-        clean::KeywordItem(ref k) => item_keyword(fmt, cx, item, k),
-        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(fmt, cx, item, e),
-        clean::TraitAliasItem(ref ta) => item_trait_alias(fmt, cx, item, ta),
+            item_static(buf, cx, item, i),
+        clean::ConstantItem(ref c) => item_constant(buf, cx, item, c),
+        clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
+        clean::KeywordItem(ref k) => item_keyword(buf, cx, item, k),
+        clean::OpaqueTyItem(ref e, _) => item_opaque_ty(buf, cx, item, e),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
         _ => {
             // We don't generate pages for any other type.
             unreachable!();
         }
     }
-    })
 }
 
 fn item_path(ty: ItemType, name: &str) -> String {
@@ -2333,24 +2331,23 @@ fn shorten(s: String) -> String {
     }
 }
 
-fn document(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item) -> fmt::Result {
+fn document(w: &mut Buffer, cx: &Context, item: &clean::Item) {
     if let Some(ref name) = item.name {
         info!("Documenting {}", name);
     }
-    document_stability(w, cx, item, false)?;
-    document_full(w, item, cx, "", false)?;
-    Ok(())
+    document_stability(w, cx, item, false);
+    document_full(w, item, cx, "", false);
 }
 
 /// Render md_text as markdown.
 fn render_markdown(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     md_text: &str,
     links: Vec<(String, String)>,
     prefix: &str,
     is_hidden: bool,
-) -> fmt::Result {
+) {
     let mut ids = cx.id_map.borrow_mut();
     write!(w, "<div class='docblock{}'>{}{}</div>",
            if is_hidden { " hidden" } else { "" },
@@ -2360,13 +2357,13 @@ fn render_markdown(
 }
 
 fn document_short(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     item: &clean::Item,
     link: AssocItemLink<'_>,
     prefix: &str,
     is_hidden: bool,
-) -> fmt::Result {
+) {
     if let Some(s) = item.doc_value() {
         let markdown = if s.contains('\n') {
             format!("{} [Read more]({})",
@@ -2374,46 +2371,41 @@ fn document_short(
         } else {
             plain_summary_line(Some(s))
         };
-        render_markdown(w, cx, &markdown, item.links(), prefix, is_hidden)?;
+        render_markdown(w, cx, &markdown, item.links(), prefix, is_hidden);
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock{}'>{}</div>",
                if is_hidden { " hidden" } else { "" },
-               prefix)?;
+               prefix);
     }
-    Ok(())
 }
 
-fn document_full(w: &mut fmt::Formatter<'_>, item: &clean::Item,
-                 cx: &Context, prefix: &str, is_hidden: bool) -> fmt::Result {
+fn document_full(w: &mut Buffer, item: &clean::Item, cx: &Context, prefix: &str, is_hidden: bool) {
     if let Some(s) = cx.shared.maybe_collapsed_doc_value(item) {
         debug!("Doc block: =====\n{}\n=====", s);
-        render_markdown(w, cx, &*s, item.links(), prefix, is_hidden)?;
+        render_markdown(w, cx, &*s, item.links(), prefix, is_hidden);
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock{}'>{}</div>",
                if is_hidden { " hidden" } else { "" },
-               prefix)?;
+               prefix);
     }
-    Ok(())
 }
 
-fn document_stability(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item,
-                      is_hidden: bool) -> fmt::Result {
+fn document_stability(w: &mut Buffer, cx: &Context, item: &clean::Item, is_hidden: bool) {
     let stabilities = short_stability(item, cx);
     if !stabilities.is_empty() {
-        write!(w, "<div class='stability{}'>", if is_hidden { " hidden" } else { "" })?;
+        write!(w, "<div class='stability{}'>", if is_hidden { " hidden" } else { "" });
         for stability in stabilities {
-            write!(w, "{}", stability)?;
+            write!(w, "{}", stability);
         }
-        write!(w, "</div>")?;
+        write!(w, "</div>");
     }
-    Ok(())
 }
 
 fn document_non_exhaustive_header(item: &clean::Item) -> &str {
     if item.is_non_exhaustive() { " (Non-exhaustive)" } else { "" }
 }
 
-fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fmt::Result {
+fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
     if item.is_non_exhaustive() {
         write!(w, "<div class='docblock non-exhaustive non-exhaustive-{}'>", {
             if item.is_struct() {
@@ -2425,31 +2417,29 @@ fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fm
             } else {
                 "type"
             }
-        })?;
+        });
 
         if item.is_struct() {
             write!(w, "Non-exhaustive structs could have additional fields added in future. \
                        Therefore, non-exhaustive structs cannot be constructed in external crates \
                        using the traditional <code>Struct {{ .. }}</code> syntax; cannot be \
                        matched against without a wildcard <code>..</code>; and \
-                       struct update syntax will not work.")?;
+                       struct update syntax will not work.");
         } else if item.is_enum() {
             write!(w, "Non-exhaustive enums could have additional variants added in future. \
                        Therefore, when matching against variants of non-exhaustive enums, an \
-                       extra wildcard arm must be added to account for any future variants.")?;
+                       extra wildcard arm must be added to account for any future variants.");
         } else if item.is_variant() {
             write!(w, "Non-exhaustive enum variants could have additional fields added in future. \
                        Therefore, non-exhaustive enum variants cannot be constructed in external \
-                       crates and cannot be matched against.")?;
+                       crates and cannot be matched against.");
         } else {
             write!(w, "This type will require a wildcard arm in any match statements or \
-                       constructors.")?;
+                       constructors.");
         }
 
-        write!(w, "</div>")?;
+        write!(w, "</div>");
     }
-
-    Ok(())
 }
 
 fn name_key(name: &str) -> (&str, u64, usize) {
@@ -2473,9 +2463,8 @@ fn name_key(name: &str) -> (&str, u64, usize) {
     }
 }
 
-fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
-               item: &clean::Item, items: &[clean::Item]) -> fmt::Result {
-    document(w, cx, item)?;
+fn item_module(w: &mut Buffer, cx: &Context, item: &clean::Item, items: &[clean::Item]) {
+    document(w, cx, item);
 
     let mut indices = (0..items.len()).filter(|i| !items[*i].is_stripped()).collect::<Vec<usize>>();
 
@@ -2566,13 +2555,13 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
             curty = myty;
         } else if myty != curty {
             if curty.is_some() {
-                write!(w, "</table>")?;
+                write!(w, "</table>");
             }
             curty = myty;
             let (short, name) = item_ty_to_strs(&myty.unwrap());
             write!(w, "<h2 id='{id}' class='section-header'>\
                        <a href=\"#{id}\">{name}</a></h2>\n<table>",
-                   id = cx.derive_id(short.to_owned()), name = name)?;
+                   id = cx.derive_id(short.to_owned()), name = name);
         }
 
         match myitem.inner {
@@ -2584,20 +2573,20 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
                         write!(w, "<tr><td><code>{}extern crate {} as {};",
                                VisSpace(&myitem.visibility),
                                anchor(myitem.def_id, src),
-                               name)?
+                               name)
                     }
                     None => {
                         write!(w, "<tr><td><code>{}extern crate {};",
                                VisSpace(&myitem.visibility),
-                               anchor(myitem.def_id, name))?
+                               anchor(myitem.def_id, name))
                     }
                 }
-                write!(w, "</code></td></tr>")?;
+                write!(w, "</code></td></tr>");
             }
 
             clean::ImportItem(ref import) => {
                 write!(w, "<tr><td><code>{}{}</code></td></tr>",
-                       VisSpace(&myitem.visibility), *import)?;
+                       VisSpace(&myitem.visibility), *import);
             }
 
             _ => {
@@ -2642,15 +2631,14 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
                                 })
                                 .collect::<Vec<_>>()
                                 .join(" "),
-                      )?;
+                      );
             }
         }
     }
 
     if curty.is_some() {
-        write!(w, "</table>")?;
+        write!(w, "</table>");
     }
-    Ok(())
 }
 
 /// Render the stability and deprecation tags that are displayed in the item's summary at the
@@ -2799,33 +2787,30 @@ fn short_stability(item: &clean::Item, cx: &Context) -> Vec<String> {
     stability
 }
 
-fn item_constant(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                 c: &clean::Constant) -> fmt::Result {
-    write!(w, "<pre class='rust const'>")?;
-    render_attributes(w, it, false)?;
+fn item_constant(w: &mut Buffer, cx: &Context, it: &clean::Item, c: &clean::Constant) {
+    write!(w, "<pre class='rust const'>");
+    render_attributes(w, it, false);
     write!(w, "{vis}const \
                {name}: {typ}</pre>",
            vis = VisSpace(&it.visibility),
            name = it.name.as_ref().unwrap(),
-           typ = c.type_)?;
+           typ = c.type_);
     document(w, cx, it)
 }
 
-fn item_static(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Static) -> fmt::Result {
-    write!(w, "<pre class='rust static'>")?;
-    render_attributes(w, it, false)?;
+fn item_static(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Static) {
+    write!(w, "<pre class='rust static'>");
+    render_attributes(w, it, false);
     write!(w, "{vis}static {mutability}\
                {name}: {typ}</pre>",
            vis = VisSpace(&it.visibility),
            mutability = MutableSpace(s.mutability),
            name = it.name.as_ref().unwrap(),
-           typ = s.type_)?;
+           typ = s.type_);
     document(w, cx, it)
 }
 
-fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                 f: &clean::Function) -> fmt::Result {
+fn item_function(w: &mut Buffer, cx: &Context, it: &clean::Item, f: &clean::Function) {
     let header_len = format!(
         "{}{}{}{}{:#}fn {}{:#}",
         VisSpace(&it.visibility),
@@ -2836,8 +2821,8 @@ fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
         it.name.as_ref().unwrap(),
         f.generics
     ).len();
-    write!(w, "{}<pre class='rust fn'>", render_spotlight_traits(it)?)?;
-    render_attributes(w, it, false)?;
+    write!(w, "{}<pre class='rust fn'>", render_spotlight_traits(it));
+    render_attributes(w, it, false);
     write!(w,
            "{vis}{constness}{unsafety}{asyncness}{abi}fn \
            {name}{generics}{decl}{where_clause}</pre>",
@@ -2854,12 +2839,12 @@ fn item_function(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
               header_len,
               indent: 0,
               asyncness: f.header.asyncness,
-           })?;
+           });
     document(w, cx, it)
 }
 
-fn render_implementor(cx: &Context, implementor: &Impl, w: &mut fmt::Formatter<'_>,
-                      implementor_dups: &FxHashMap<&str, (DefId, bool)>) -> fmt::Result {
+fn render_implementor(cx: &Context, implementor: &Impl, w: &mut Buffer,
+                      implementor_dups: &FxHashMap<&str, (DefId, bool)>) {
     // If there's already another implementor that has the same abbridged name, use the
     // full path, for example in `std::iter::ExactSizeIterator`
     let use_absolute = match implementor.inner_impl().for_ {
@@ -2871,20 +2856,18 @@ fn render_implementor(cx: &Context, implementor: &Impl, w: &mut fmt::Formatter<'
         _ => false,
     };
     render_impl(w, cx, implementor, AssocItemLink::Anchor(None), RenderMode::Normal,
-                implementor.impl_item.stable_since(), false, Some(use_absolute), false, false)?;
-    Ok(())
+                implementor.impl_item.stable_since(), false, Some(use_absolute), false, false);
 }
 
-fn render_impls(cx: &Context, w: &mut fmt::Formatter<'_>,
+fn render_impls(cx: &Context, w: &mut Buffer,
                 traits: &[&&Impl],
-                containing_item: &clean::Item) -> fmt::Result {
+                containing_item: &clean::Item) {
     for i in traits {
         let did = i.trait_did().unwrap();
         let assoc_link = AssocItemLink::GotoSource(did, &i.inner_impl().provided_trait_methods);
         render_impl(w, cx, i, assoc_link,
-                    RenderMode::Normal, containing_item.stable_since(), true, None, false, true)?;
+                    RenderMode::Normal, containing_item.stable_since(), true, None, false, true);
     }
-    Ok(())
 }
 
 fn bounds(t_bounds: &[clean::GenericBound], trait_alias: bool) -> String {
@@ -2912,11 +2895,11 @@ fn compare_impl<'a, 'b>(lhs: &'a &&Impl, rhs: &'b &&Impl) -> Ordering {
 }
 
 fn item_trait(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     it: &clean::Item,
     t: &clean::Trait,
-) -> fmt::Result {
+) {
     let bounds = bounds(&t.bounds, false);
     let types = t.items.iter().filter(|m| m.is_associated_type()).collect::<Vec<_>>();
     let consts = t.items.iter().filter(|m| m.is_associated_const()).collect::<Vec<_>>();
@@ -2925,146 +2908,144 @@ fn item_trait(
 
     // Output the trait definition
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust trait'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust trait'>");
+        render_attributes(w, it, true);
         write!(w, "{}{}{}trait {}{}{}",
                VisSpace(&it.visibility),
                UnsafetySpace(t.unsafety),
                if t.is_auto { "auto " } else { "" },
                it.name.as_ref().unwrap(),
                t.generics,
-               bounds)?;
+               bounds);
 
         if !t.generics.where_predicates.is_empty() {
-            write!(w, "{}", WhereClause { gens: &t.generics, indent: 0, end_newline: true })?;
+            write!(w, "{}", WhereClause { gens: &t.generics, indent: 0, end_newline: true });
         } else {
-            write!(w, " ")?;
+            write!(w, " ");
         }
 
         if t.items.is_empty() {
-            write!(w, "{{ }}")?;
+            write!(w, "{{ }}");
         } else {
             // FIXME: we should be using a derived_id for the Anchors here
-            write!(w, "{{\n")?;
+            write!(w, "{{\n");
             for t in &types {
-                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
             }
             if !types.is_empty() && !consts.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for t in &consts {
-                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
             }
             if !consts.is_empty() && !required.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for (pos, m) in required.iter().enumerate() {
-                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait)?;
-                write!(w, ";\n")?;
+                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait);
+                write!(w, ";\n");
 
                 if pos < required.len() - 1 {
-                   write!(w, "<div class='item-spacer'></div>")?;
+                   write!(w, "<div class='item-spacer'></div>");
                 }
             }
             if !required.is_empty() && !provided.is_empty() {
-                w.write_str("\n")?;
+                w.write_str("\n");
             }
             for (pos, m) in provided.iter().enumerate() {
-                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait)?;
+                render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait);
                 match m.inner {
                     clean::MethodItem(ref inner) if !inner.generics.where_predicates.is_empty() => {
-                        write!(w, ",\n    {{ ... }}\n")?;
+                        write!(w, ",\n    {{ ... }}\n");
                     },
                     _ => {
-                        write!(w, " {{ ... }}\n")?;
+                        write!(w, " {{ ... }}\n");
                     },
                 }
                 if pos < provided.len() - 1 {
-                   write!(w, "<div class='item-spacer'></div>")?;
+                   write!(w, "<div class='item-spacer'></div>");
                 }
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         write!(w, "</pre>")
-    })?;
+    });
 
     // Trait documentation
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     fn write_small_section_header(
-        w: &mut fmt::Formatter<'_>,
+        w: &mut Buffer,
         id: &str,
         title: &str,
         extra_content: &str,
-    ) -> fmt::Result {
+    ) {
         write!(w, "
             <h2 id='{0}' class='small-section-header'>\
               {1}<a href='#{0}' class='anchor'></a>\
             </h2>{2}", id, title, extra_content)
     }
 
-    fn write_loading_content(w: &mut fmt::Formatter<'_>, extra_content: &str) -> fmt::Result {
+    fn write_loading_content(w: &mut Buffer, extra_content: &str) {
         write!(w, "{}<span class='loading-content'>Loading content...</span>", extra_content)
     }
 
-    fn trait_item(w: &mut fmt::Formatter<'_>, cx: &Context, m: &clean::Item, t: &clean::Item)
-                  -> fmt::Result {
+    fn trait_item(w: &mut Buffer, cx: &Context, m: &clean::Item, t: &clean::Item) {
         let name = m.name.as_ref().unwrap();
         let item_type = m.type_();
         let id = cx.derive_id(format!("{}.{}", item_type, name));
         let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
         write!(w, "<h3 id='{id}' class='method'>{extra}<code id='{ns_id}'>",
-               extra = render_spotlight_traits(m)?,
+               extra = render_spotlight_traits(m),
                id = id,
-               ns_id = ns_id)?;
-        render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl)?;
-        write!(w, "</code>")?;
-        render_stability_since(w, m, t)?;
-        write!(w, "</h3>")?;
-        document(w, cx, m)?;
-        Ok(())
+               ns_id = ns_id);
+        render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl);
+        write!(w, "</code>");
+        render_stability_since(w, m, t);
+        write!(w, "</h3>");
+        document(w, cx, m);
     }
 
     if !types.is_empty() {
         write_small_section_header(w, "associated-types", "Associated Types",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for t in &types {
-            trait_item(w, cx, *t, it)?;
+            trait_item(w, cx, *t, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     if !consts.is_empty() {
         write_small_section_header(w, "associated-const", "Associated Constants",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for t in &consts {
-            trait_item(w, cx, *t, it)?;
+            trait_item(w, cx, *t, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     // Output the documentation for each function individually
     if !required.is_empty() {
         write_small_section_header(w, "required-methods", "Required methods",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for m in &required {
-            trait_item(w, cx, *m, it)?;
+            trait_item(w, cx, *m, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
     if !provided.is_empty() {
         write_small_section_header(w, "provided-methods", "Provided methods",
-                                   "<div class='methods'>")?;
+                                   "<div class='methods'>");
         for m in &provided {
-            trait_item(w, cx, *m, it)?;
+            trait_item(w, cx, *m, it);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
     }
 
     // If there are methods directly on this trait object, render them here.
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)?;
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All);
 
     let cache = cache();
 
@@ -3103,7 +3084,7 @@ fn item_trait(
         concrete.sort_by(compare_impl);
 
         if !foreign.is_empty() {
-            write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "")?;
+            write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "");
 
             for implementor in foreign {
                 let assoc_link = AssocItemLink::GotoSource(
@@ -3112,44 +3093,44 @@ fn item_trait(
                 );
                 render_impl(w, cx, &implementor, assoc_link,
                             RenderMode::Normal, implementor.impl_item.stable_since(), false,
-                            None, true, false)?;
+                            None, true, false);
             }
-            write_loading_content(w, "")?;
+            write_loading_content(w, "");
         }
 
         write_small_section_header(w, "implementors", "Implementors",
-                                   "<div class='item-list' id='implementors-list'>")?;
+                                   "<div class='item-list' id='implementors-list'>");
         for implementor in concrete {
-            render_implementor(cx, implementor, w, &implementor_dups)?;
+            render_implementor(cx, implementor, w, &implementor_dups);
         }
-        write_loading_content(w, "</div>")?;
+        write_loading_content(w, "</div>");
 
         if t.auto {
             write_small_section_header(w, "synthetic-implementors", "Auto implementors",
-                                       "<div class='item-list' id='synthetic-implementors-list'>")?;
+                                       "<div class='item-list' id='synthetic-implementors-list'>");
             for implementor in synthetic {
                 synthetic_types.extend(
                     collect_paths_for_type(implementor.inner_impl().for_.clone())
                 );
-                render_implementor(cx, implementor, w, &implementor_dups)?;
+                render_implementor(cx, implementor, w, &implementor_dups);
             }
-            write_loading_content(w, "</div>")?;
+            write_loading_content(w, "</div>");
         }
     } else {
         // even without any implementations to write in, we still want the heading and list, so the
         // implementors javascript file pulled in below has somewhere to write the impls into
         write_small_section_header(w, "implementors", "Implementors",
-                                   "<div class='item-list' id='implementors-list'>")?;
-        write_loading_content(w, "</div>")?;
+                                   "<div class='item-list' id='implementors-list'>");
+        write_loading_content(w, "</div>");
 
         if t.auto {
             write_small_section_header(w, "synthetic-implementors", "Auto implementors",
-                                       "<div class='item-list' id='synthetic-implementors-list'>")?;
-            write_loading_content(w, "</div>")?;
+                                       "<div class='item-list' id='synthetic-implementors-list'>");
+            write_loading_content(w, "</div>");
         }
     }
     write!(w, r#"<script type="text/javascript">window.inlined_types=new Set({});</script>"#,
-           as_json(&synthetic_types))?;
+           as_json(&synthetic_types));
 
     write!(w, r#"<script type="text/javascript" async
                          src="{root_path}/implementors/{path}/{ty}.{name}.js">
@@ -3162,8 +3143,7 @@ fn item_trait(
                path[..path.len() - 1].join("/")
            },
            ty = it.type_().css_class(),
-           name = *it.name.as_ref().unwrap())?;
-    Ok(())
+           name = *it.name.as_ref().unwrap());
 }
 
 fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
@@ -3185,70 +3165,60 @@ fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
     }
 }
 
-fn assoc_const(w: &mut fmt::Formatter<'_>,
+fn assoc_const(w: &mut Buffer,
                it: &clean::Item,
                ty: &clean::Type,
                _default: Option<&String>,
                link: AssocItemLink<'_>,
-               extra: &str) -> fmt::Result {
+               extra: &str) {
     write!(w, "{}{}const <a href='{}' class=\"constant\"><b>{}</b></a>: {}",
            extra,
            VisSpace(&it.visibility),
            naive_assoc_href(it, link),
            it.name.as_ref().unwrap(),
-           ty)?;
-    Ok(())
+           ty);
 }
 
-fn assoc_type<W: fmt::Write>(w: &mut W, it: &clean::Item,
-                             bounds: &[clean::GenericBound],
-                             default: Option<&clean::Type>,
-                             link: AssocItemLink<'_>,
-                             extra: &str) -> fmt::Result {
+fn assoc_type(w: &mut Buffer, it: &clean::Item,
+              bounds: &[clean::GenericBound],
+              default: Option<&clean::Type>,
+              link: AssocItemLink<'_>,
+              extra: &str) {
     write!(w, "{}type <a href='{}' class=\"type\">{}</a>",
            extra,
            naive_assoc_href(it, link),
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if !bounds.is_empty() {
-        write!(w, ": {}", GenericBounds(bounds))?
+        write!(w, ": {}", GenericBounds(bounds))
     }
     if let Some(default) = default {
-        write!(w, " = {}", default)?;
+        write!(w, " = {}", default)
     }
-    Ok(())
 }
 
-fn render_stability_since_raw<'a, T: fmt::Write>(
-    w: &mut T,
-    ver: Option<&'a str>,
-    containing_ver: Option<&'a str>,
-) -> fmt::Result {
+fn render_stability_since_raw(w: &mut Buffer, ver: Option<&str>, containing_ver: Option<&str>) {
     if let Some(v) = ver {
         if containing_ver != ver && v.len() > 0 {
-            write!(w, "<span class='since' title='Stable since Rust version {0}'>{0}</span>", v)?
+            write!(w, "<span class='since' title='Stable since Rust version {0}'>{0}</span>", v)
         }
     }
-    Ok(())
 }
 
-fn render_stability_since(w: &mut fmt::Formatter<'_>,
-                          item: &clean::Item,
-                          containing_item: &clean::Item) -> fmt::Result {
+fn render_stability_since(w: &mut Buffer, item: &clean::Item, containing_item: &clean::Item) {
     render_stability_since_raw(w, item.stable_since(), containing_item.stable_since())
 }
 
-fn render_assoc_item(w: &mut fmt::Formatter<'_>,
+fn render_assoc_item(w: &mut Buffer,
                      item: &clean::Item,
                      link: AssocItemLink<'_>,
-                     parent: ItemType) -> fmt::Result {
-    fn method(w: &mut fmt::Formatter<'_>,
+                     parent: ItemType) {
+    fn method(w: &mut Buffer,
               meth: &clean::Item,
               header: hir::FnHeader,
               g: &clean::Generics,
               d: &clean::FnDecl,
               link: AssocItemLink<'_>,
-              parent: ItemType)
-              -> fmt::Result {
+              parent: ItemType) {
         let name = meth.name.as_ref().unwrap();
         let anchor = format!("#{}.{}", meth.type_(), name);
         let href = match link {
@@ -3283,7 +3253,7 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
         } else {
             (0, true)
         };
-        render_attributes(w, meth, false)?;
+        render_attributes(w, meth, false);
         write!(w, "{}{}{}{}{}{}{}fn <a href='{href}' class='fnname'>{name}</a>\
                    {generics}{decl}{where_clause}",
                if parent == ItemType::Trait { "    " } else { "" },
@@ -3309,7 +3279,7 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
                })
     }
     match item.inner {
-        clean::StrippedItem(..) => Ok(()),
+        clean::StrippedItem(..) => {},
         clean::TyMethodItem(ref m) => {
             method(w, item, m.header, &m.generics, &m.decl, link, parent)
         }
@@ -3328,22 +3298,21 @@ fn render_assoc_item(w: &mut fmt::Formatter<'_>,
     }
 }
 
-fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Struct) -> fmt::Result {
+fn item_struct(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Struct) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust struct'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust struct'>");
+        render_attributes(w, it, true);
         render_struct(w,
                       it,
                       Some(&s.generics),
                       s.struct_type,
                       &s.fields,
                       "",
-                      true)?;
+                      true);
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     let mut fields = s.fields.iter().filter_map(|f| {
         match f.inner {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
@@ -3354,8 +3323,8 @@ fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
         if fields.peek().is_some() {
             write!(w, "<h2 id='fields' class='fields small-section-header'>
                        Fields{}<a href='#fields' class='anchor'></a></h2>",
-                       document_non_exhaustive_header(it))?;
-            document_non_exhaustive(w, it)?;
+                       document_non_exhaustive_header(it));
+            document_non_exhaustive(w, it);
             for (field, ty) in fields {
                 let id = cx.derive_id(format!("{}.{}",
                                            ItemType::StructField,
@@ -3371,29 +3340,28 @@ fn item_struct(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                        id = id,
                        ns_id = ns_id,
                        name = field.name.as_ref().unwrap(),
-                       ty = ty)?;
-                document(w, cx, field)?;
+                       ty = ty);
+                document(w, cx, field);
             }
         }
     }
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-               s: &clean::Union) -> fmt::Result {
+fn item_union(w: &mut Buffer, cx: &Context, it: &clean::Item, s: &clean::Union) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust union'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust union'>");
+        render_attributes(w, it, true);
         render_union(w,
                      it,
                      Some(&s.generics),
                      &s.fields,
                      "",
-                     true)?;
+                     true);
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     let mut fields = s.fields.iter().filter_map(|f| {
         match f.inner {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
@@ -3402,7 +3370,7 @@ fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     }).peekable();
     if fields.peek().is_some() {
         write!(w, "<h2 id='fields' class='fields small-section-header'>
-                   Fields<a href='#fields' class='anchor'></a></h2>")?;
+                   Fields<a href='#fields' class='anchor'></a></h2>");
         for (field, ty) in fields {
             let name = field.name.as_ref().expect("union field name");
             let id = format!("{}.{}", ItemType::StructField, name);
@@ -3413,47 +3381,46 @@ fn item_union(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                    id = id,
                    name = name,
                    shortty = ItemType::StructField,
-                   ty = ty)?;
+                   ty = ty);
             if let Some(stability_class) = field.stability_class() {
                 write!(w, "<span class='stab {stab}'></span>",
-                    stab = stability_class)?;
+                    stab = stability_class);
             }
-            document(w, cx, field)?;
+            document(w, cx, field);
         }
     }
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-             e: &clean::Enum) -> fmt::Result {
+fn item_enum(w: &mut Buffer, cx: &Context, it: &clean::Item, e: &clean::Enum) {
     wrap_into_docblock(w, |w| {
-        write!(w, "<pre class='rust enum'>")?;
-        render_attributes(w, it, true)?;
+        write!(w, "<pre class='rust enum'>");
+        render_attributes(w, it, true);
         write!(w, "{}enum {}{}{}",
                VisSpace(&it.visibility),
                it.name.as_ref().unwrap(),
                e.generics,
-               WhereClause { gens: &e.generics, indent: 0, end_newline: true })?;
+               WhereClause { gens: &e.generics, indent: 0, end_newline: true });
         if e.variants.is_empty() && !e.variants_stripped {
-            write!(w, " {{}}")?;
+            write!(w, " {{}}");
         } else {
-            write!(w, " {{\n")?;
+            write!(w, " {{\n");
             for v in &e.variants {
-                write!(w, "    ")?;
+                write!(w, "    ");
                 let name = v.name.as_ref().unwrap();
                 match v.inner {
                     clean::VariantItem(ref var) => {
                         match var.kind {
-                            clean::VariantKind::CLike => write!(w, "{}", name)?,
+                            clean::VariantKind::CLike => write!(w, "{}", name),
                             clean::VariantKind::Tuple(ref tys) => {
-                                write!(w, "{}(", name)?;
+                                write!(w, "{}(", name);
                                 for (i, ty) in tys.iter().enumerate() {
                                     if i > 0 {
-                                        write!(w, ",&nbsp;")?
+                                        write!(w, ",&nbsp;")
                                     }
-                                    write!(w, "{}", *ty)?;
+                                    write!(w, "{}", *ty);
                                 }
-                                write!(w, ")")?;
+                                write!(w, ")");
                             }
                             clean::VariantKind::Struct(ref s) => {
                                 render_struct(w,
@@ -3462,29 +3429,29 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                                               s.struct_type,
                                               &s.fields,
                                               "    ",
-                                              false)?;
+                                              false);
                             }
                         }
                     }
                     _ => unreachable!()
                 }
-                write!(w, ",\n")?;
+                write!(w, ",\n");
             }
 
             if e.variants_stripped {
-                write!(w, "    // some variants omitted\n")?;
+                write!(w, "    // some variants omitted\n");
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         write!(w, "</pre>")
-    })?;
+    });
 
-    document(w, cx, it)?;
+    document(w, cx, it);
     if !e.variants.is_empty() {
         write!(w, "<h2 id='variants' class='variants small-section-header'>
                    Variants{}<a href='#variants' class='anchor'></a></h2>\n",
-                   document_non_exhaustive_header(it))?;
-        document_non_exhaustive(w, it)?;
+                   document_non_exhaustive_header(it));
+        document_non_exhaustive(w, it);
         for variant in &e.variants {
             let id = cx.derive_id(format!("{}.{}",
                                        ItemType::Variant,
@@ -3497,22 +3464,22 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                        <code id='{ns_id}'>{name}",
                    id = id,
                    ns_id = ns_id,
-                   name = variant.name.as_ref().unwrap())?;
+                   name = variant.name.as_ref().unwrap());
             if let clean::VariantItem(ref var) = variant.inner {
                 if let clean::VariantKind::Tuple(ref tys) = var.kind {
-                    write!(w, "(")?;
+                    write!(w, "(");
                     for (i, ty) in tys.iter().enumerate() {
                         if i > 0 {
-                            write!(w, ",&nbsp;")?;
+                            write!(w, ",&nbsp;");
                         }
-                        write!(w, "{}", *ty)?;
+                        write!(w, "{}", *ty);
                     }
-                    write!(w, ")")?;
+                    write!(w, ")");
                 }
             }
-            write!(w, "</code></span>")?;
-            document(w, cx, variant)?;
-            document_non_exhaustive(w, variant)?;
+            write!(w, "</code></span>");
+            document(w, cx, variant);
+            document_non_exhaustive(w, variant);
 
             use crate::clean::{Variant, VariantKind};
             if let clean::VariantItem(Variant {
@@ -3522,9 +3489,9 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                                                    ItemType::Variant,
                                                    variant.name.as_ref().unwrap()));
                 write!(w, "<span class='autohide sub-variant' id='{id}'>",
-                       id = variant_id)?;
+                       id = variant_id);
                 write!(w, "<h3>Fields of <b>{name}</b></h3><div>",
-                       name = variant.name.as_ref().unwrap())?;
+                       name = variant.name.as_ref().unwrap());
                 for field in &s.fields {
                     use crate::clean::StructFieldItem;
                     if let StructFieldItem(ref ty) = field.inner {
@@ -3543,17 +3510,16 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
                                id = id,
                                ns_id = ns_id,
                                f = field.name.as_ref().unwrap(),
-                               t = *ty)?;
-                        document(w, cx, field)?;
+                               t = *ty);
+                        document(w, cx, field);
                     }
                 }
-                write!(w, "</div></span>")?;
+                write!(w, "</div></span>");
             }
-            render_stability_since(w, variant, it)?;
+            render_stability_since(w, variant, it);
         }
     }
-    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)?;
-    Ok(())
+    render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
 fn render_attribute(attr: &ast::MetaItem) -> Option<String> {
@@ -3596,7 +3562,7 @@ const ATTRIBUTE_WHITELIST: &'static [Symbol] = &[
 //     #[bar] <---- not "top" attribute
 //     bar: usize,
 // }
-fn render_attributes(w: &mut dyn fmt::Write, it: &clean::Item, top: bool) -> fmt::Result {
+fn render_attributes(w: &mut Buffer, it: &clean::Item, top: bool) {
     let mut attrs = String::new();
 
     for attr in &it.attrs.other_attrs {
@@ -3609,117 +3575,114 @@ fn render_attributes(w: &mut dyn fmt::Write, it: &clean::Item, top: bool) -> fmt
     }
     if attrs.len() > 0 {
         write!(w, "<span class=\"docblock attributes{}\">{}</span>",
-               if top { " top-attr" } else { "" }, &attrs)?;
+               if top { " top-attr" } else { "" }, &attrs);
     }
-    Ok(())
 }
 
-fn render_struct(w: &mut fmt::Formatter<'_>, it: &clean::Item,
+fn render_struct(w: &mut Buffer, it: &clean::Item,
                  g: Option<&clean::Generics>,
                  ty: doctree::StructType,
                  fields: &[clean::Item],
                  tab: &str,
-                 structhead: bool) -> fmt::Result {
+                 structhead: bool) {
     write!(w, "{}{}{}",
            VisSpace(&it.visibility),
            if structhead {"struct "} else {""},
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if let Some(g) = g {
-        write!(w, "{}", g)?
+        write!(w, "{}", g)
     }
     match ty {
         doctree::Plain => {
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })
             }
             let mut has_visible_fields = false;
-            write!(w, " {{")?;
+            write!(w, " {{");
             for field in fields {
                 if let clean::StructFieldItem(ref ty) = field.inner {
                     write!(w, "\n{}    {}{}: {},",
                            tab,
                            VisSpace(&field.visibility),
                            field.name.as_ref().unwrap(),
-                           *ty)?;
+                           *ty);
                     has_visible_fields = true;
                 }
             }
 
             if has_visible_fields {
                 if it.has_stripped_fields().unwrap() {
-                    write!(w, "\n{}    // some fields omitted", tab)?;
+                    write!(w, "\n{}    // some fields omitted", tab);
                 }
-                write!(w, "\n{}", tab)?;
+                write!(w, "\n{}", tab);
             } else if it.has_stripped_fields().unwrap() {
                 // If there are no visible fields we can just display
                 // `{ /* fields omitted */ }` to save space.
-                write!(w, " /* fields omitted */ ")?;
+                write!(w, " /* fields omitted */ ");
             }
-            write!(w, "}}")?;
+            write!(w, "}}");
         }
         doctree::Tuple => {
-            write!(w, "(")?;
+            write!(w, "(");
             for (i, field) in fields.iter().enumerate() {
                 if i > 0 {
-                    write!(w, ", ")?;
+                    write!(w, ", ");
                 }
                 match field.inner {
                     clean::StrippedItem(box clean::StructFieldItem(..)) => {
-                        write!(w, "_")?
+                        write!(w, "_")
                     }
                     clean::StructFieldItem(ref ty) => {
-                        write!(w, "{}{}", VisSpace(&field.visibility), *ty)?
+                        write!(w, "{}{}", VisSpace(&field.visibility), *ty)
                     }
                     _ => unreachable!()
                 }
             }
-            write!(w, ")")?;
+            write!(w, ")");
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })
             }
-            write!(w, ";")?;
+            write!(w, ";");
         }
         doctree::Unit => {
             // Needed for PhantomData.
             if let Some(g) = g {
-                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })?
+                write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: false })
             }
-            write!(w, ";")?;
+            write!(w, ";");
         }
     }
-    Ok(())
 }
 
-fn render_union(w: &mut fmt::Formatter<'_>, it: &clean::Item,
+fn render_union(w: &mut Buffer, it: &clean::Item,
                 g: Option<&clean::Generics>,
                 fields: &[clean::Item],
                 tab: &str,
-                structhead: bool) -> fmt::Result {
+                structhead: bool) {
     write!(w, "{}{}{}",
            VisSpace(&it.visibility),
            if structhead {"union "} else {""},
-           it.name.as_ref().unwrap())?;
+           it.name.as_ref().unwrap());
     if let Some(g) = g {
-        write!(w, "{}", g)?;
-        write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true })?;
+        write!(w, "{}", g);
+        write!(w, "{}", WhereClause { gens: g, indent: 0, end_newline: true });
     }
 
-    write!(w, " {{\n{}", tab)?;
+    write!(w, " {{\n{}", tab);
     for field in fields {
         if let clean::StructFieldItem(ref ty) = field.inner {
             write!(w, "    {}{}: {},\n{}",
                    VisSpace(&field.visibility),
                    field.name.as_ref().unwrap(),
                    *ty,
-                   tab)?;
+                   tab);
         }
     }
 
     if it.has_stripped_fields().unwrap() {
-        write!(w, "    // some fields omitted\n{}", tab)?;
+        write!(w, "    // some fields omitted\n{}", tab);
     }
-    write!(w, "}}")?;
-    Ok(())
+    write!(w, "}}");
 }
 
 #[derive(Copy, Clone)]
@@ -3748,15 +3711,15 @@ enum RenderMode {
     ForDeref { mut_: bool },
 }
 
-fn render_assoc_items(w: &mut fmt::Formatter<'_>,
+fn render_assoc_items(w: &mut Buffer,
                       cx: &Context,
                       containing_item: &clean::Item,
                       it: DefId,
-                      what: AssocItemRender<'_>) -> fmt::Result {
+                      what: AssocItemRender<'_>) {
     let c = cache();
     let v = match c.impls.get(&it) {
         Some(v) => v,
-        None => return Ok(()),
+        None => return,
     };
     let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| {
         i.inner_impl().trait_.is_none()
@@ -3768,7 +3731,7 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                     <h2 id='methods' class='small-section-header'>\
                       Methods<a href='#methods' class='anchor'></a>\
                     </h2>\
-                ")?;
+                ");
                 RenderMode::Normal
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
@@ -3777,17 +3740,17 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                       Methods from {}&lt;Target = {}&gt;\
                       <a href='#deref-methods' class='anchor'></a>\
                     </h2>\
-                ", trait_, type_)?;
+                ", trait_, type_);
                 RenderMode::ForDeref { mut_: deref_mut_ }
             }
         };
         for i in &non_trait {
             render_impl(w, cx, i, AssocItemLink::Anchor(None), render_mode,
-                        containing_item.stable_since(), true, None, false, true)?;
+                        containing_item.stable_since(), true, None, false, true);
         }
     }
     if let AssocItemRender::DerefFor { .. } = what {
-        return Ok(());
+        return;
     }
     if !traits.is_empty() {
         let deref_impl = traits.iter().find(|t| {
@@ -3797,31 +3760,25 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
             let has_deref_mut = traits.iter().find(|t| {
                 t.inner_impl().trait_.def_id() == c.deref_mut_trait_did
             }).is_some();
-            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut)?;
+            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut);
         }
 
         let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) = traits
             .iter()
             .partition(|t| t.inner_impl().synthetic);
-        let (blanket_impl, concrete) = concrete
+        let (blanket_impl, concrete): (Vec<&&Impl>, _) = concrete
             .into_iter()
             .partition(|t| t.inner_impl().blanket_impl.is_some());
 
-        struct RendererStruct<'a, 'b, 'c>(&'a Context, Vec<&'b &'b Impl>, &'c clean::Item);
-
-        impl<'a, 'b, 'c> fmt::Display for RendererStruct<'a, 'b, 'c> {
-        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-            render_impls(self.0, fmt, &self.1, self.2)
-        }
-        }
-
-        let impls = RendererStruct(cx, concrete, containing_item).to_string();
+        let mut impls = Buffer::empty_from(&w);
+        render_impls(cx, &mut impls, &concrete, containing_item);
+        let impls = impls.into_inner();
         if !impls.is_empty() {
             write!(w, "\
                 <h2 id='implementations' class='small-section-header'>\
                   Trait Implementations<a href='#implementations' class='anchor'></a>\
                 </h2>\
-                <div id='implementations-list'>{}</div>", impls)?;
+                <div id='implementations-list'>{}</div>", impls);
         }
 
         if !synthetic.is_empty() {
@@ -3831,9 +3788,9 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                   <a href='#synthetic-implementations' class='anchor'></a>\
                 </h2>\
                 <div id='synthetic-implementations-list'>\
-            ")?;
-            render_impls(cx, w, &synthetic, containing_item)?;
-            write!(w, "</div>")?;
+            ");
+            render_impls(cx, w, &synthetic, containing_item);
+            write!(w, "</div>");
         }
 
         if !blanket_impl.is_empty() {
@@ -3843,16 +3800,15 @@ fn render_assoc_items(w: &mut fmt::Formatter<'_>,
                   <a href='#blanket-implementations' class='anchor'></a>\
                 </h2>\
                 <div id='blanket-implementations-list'>\
-            ")?;
-            render_impls(cx, w, &blanket_impl, containing_item)?;
-            write!(w, "</div>")?;
+            ");
+            render_impls(cx, w, &blanket_impl, containing_item);
+            write!(w, "</div>");
         }
     }
-    Ok(())
 }
 
-fn render_deref_methods(w: &mut fmt::Formatter<'_>, cx: &Context, impl_: &Impl,
-                        container_item: &clean::Item, deref_mut: bool) -> fmt::Result {
+fn render_deref_methods(w: &mut Buffer, cx: &Context, impl_: &Impl,
+                        container_item: &clean::Item, deref_mut: bool) {
     let deref_type = impl_.inner_impl().trait_.as_ref().unwrap();
     let target = impl_.inner_impl().items.iter().filter_map(|item| {
         match item.inner {
@@ -3867,10 +3823,9 @@ fn render_deref_methods(w: &mut fmt::Formatter<'_>, cx: &Context, impl_: &Impl,
     } else {
         if let Some(prim) = target.primitive_type() {
             if let Some(&did) = cache().primitive_locations.get(&prim) {
-                render_assoc_items(w, cx, container_item, did, what)?;
+                render_assoc_items(w, cx, container_item, did, what);
             }
         }
-        Ok(())
     }
 }
 
@@ -3900,7 +3855,7 @@ fn should_render_item(item: &clean::Item, deref_mut_: bool) -> bool {
     }
 }
 
-fn render_spotlight_traits(item: &clean::Item) -> Result<String, fmt::Error> {
+fn render_spotlight_traits(item: &clean::Item) -> String {
     let mut out = String::new();
 
     match item.inner {
@@ -3908,16 +3863,16 @@ fn render_spotlight_traits(item: &clean::Item) -> Result<String, fmt::Error> {
         clean::TyMethodItem(clean::TyMethod { ref decl, .. }) |
         clean::MethodItem(clean::Method { ref decl, .. }) |
         clean::ForeignFunctionItem(clean::Function { ref decl, .. }) => {
-            out = spotlight_decl(decl)?;
+            out = spotlight_decl(decl);
         }
         _ => {}
     }
 
-    Ok(out)
+    out
 }
 
-fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
-    let mut out = String::new();
+fn spotlight_decl(decl: &clean::FnDecl) -> String {
+    let mut out = Buffer::html();
     let mut trait_ = String::new();
 
     if let Some(did) = decl.output.def_id() {
@@ -3943,7 +3898,7 @@ fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
                             assoc_type(&mut out, it, &[],
                                        Some(&tydef.type_),
                                        AssocItemLink::GotoSource(t_did, &FxHashSet::default()),
-                                       "")?;
+                                       "");
                             out.push_str(";</span>");
                         }
                     }
@@ -3960,13 +3915,13 @@ fn spotlight_decl(decl: &clean::FnDecl) -> Result<String, fmt::Error> {
         out.push_str("</code></div></div>");
     }
 
-    Ok(out)
+    out.into_inner()
 }
 
-fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocItemLink<'_>,
+fn render_impl(w: &mut Buffer, cx: &Context, i: &Impl, link: AssocItemLink<'_>,
                render_mode: RenderMode, outer_version: Option<&str>, show_def_docs: bool,
                use_absolute: Option<bool>, is_on_foreign_type: bool,
-               show_default_items: bool) -> fmt::Result {
+               show_default_items: bool) {
     if render_mode == RenderMode::Normal {
         let id = cx.derive_id(match i.inner_impl().trait_ {
             Some(ref t) => if is_on_foreign_type {
@@ -3977,45 +3932,45 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
             None => "impl".to_string(),
         });
         if let Some(use_absolute) = use_absolute {
-            write!(w, "<h3 id='{}' class='impl'><code class='in-band'>", id)?;
-            fmt_impl_for_trait_page(&i.inner_impl(), w, use_absolute)?;
+            write!(w, "<h3 id='{}' class='impl'><code class='in-band'>", id);
+            fmt_impl_for_trait_page(&i.inner_impl(), w, use_absolute);
             if show_def_docs {
                 for it in &i.inner_impl().items {
                     if let clean::TypedefItem(ref tydef, _) = it.inner {
-                        write!(w, "<span class=\"where fmt-newline\">  ")?;
+                        write!(w, "<span class=\"where fmt-newline\">  ");
                         assoc_type(w, it, &vec![], Some(&tydef.type_),
                                    AssocItemLink::Anchor(None),
-                                   "")?;
-                        write!(w, ";</span>")?;
+                                   "");
+                        write!(w, ";</span>");
                     }
                 }
             }
-            write!(w, "</code>")?;
+            write!(w, "</code>");
         } else {
             write!(w, "<h3 id='{}' class='impl'><code class='in-band'>{}</code>",
                 id, i.inner_impl()
-            )?;
+            );
         }
-        write!(w, "<a href='#{}' class='anchor'></a>", id)?;
+        write!(w, "<a href='#{}' class='anchor'></a>", id);
         let since = i.impl_item.stability.as_ref().map(|s| &s.since[..]);
-        render_stability_since_raw(w, since, outer_version)?;
+        render_stability_since_raw(w, since, outer_version);
         if let Some(l) = cx.src_href(&i.impl_item) {
             write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                   l, "goto source code")?;
+                   l, "goto source code");
         }
-        write!(w, "</h3>")?;
+        write!(w, "</h3>");
         if let Some(ref dox) = cx.shared.maybe_collapsed_doc_value(&i.impl_item) {
             let mut ids = cx.id_map.borrow_mut();
             write!(w, "<div class='docblock'>{}</div>",
                    Markdown(&*dox, &i.impl_item.links(), &mut ids,
-                            cx.codes, cx.edition, &cx.playground).to_string())?;
+                            cx.codes, cx.edition, &cx.playground).to_string());
         }
     }
 
-    fn doc_impl_item(w: &mut fmt::Formatter<'_>, cx: &Context, item: &clean::Item,
+    fn doc_impl_item(w: &mut Buffer, cx: &Context, item: &clean::Item,
                      link: AssocItemLink<'_>, render_mode: RenderMode,
                      is_default_item: bool, outer_version: Option<&str>,
-                     trait_: Option<&clean::Trait>, show_def_docs: bool) -> fmt::Result {
+                     trait_: Option<&clean::Trait>, show_def_docs: bool) {
         let item_type = item.type_();
         let name = item.name.as_ref().unwrap();
 
@@ -4039,50 +3994,50 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                 if render_method_item {
                     let id = cx.derive_id(format!("{}.{}", item_type, name));
                     let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                    write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                    write!(w, "{}", spotlight_decl(decl)?)?;
-                    write!(w, "<code id='{}'>", ns_id)?;
-                    render_assoc_item(w, item, link.anchor(&id), ItemType::Impl)?;
-                    write!(w, "</code>")?;
-                    render_stability_since_raw(w, item.stable_since(), outer_version)?;
+                    write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                    write!(w, "{}", spotlight_decl(decl));
+                    write!(w, "<code id='{}'>", ns_id);
+                    render_assoc_item(w, item, link.anchor(&id), ItemType::Impl);
+                    write!(w, "</code>");
+                    render_stability_since_raw(w, item.stable_since(), outer_version);
                     if let Some(l) = cx.src_href(item) {
                         write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                               l, "goto source code")?;
+                               l, "goto source code");
                     }
-                    write!(w, "</h4>")?;
+                    write!(w, "</h4>");
                 }
             }
             clean::TypedefItem(ref tydef, _) => {
                 let id = cx.derive_id(format!("{}.{}", ItemType::AssocType, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_type(w, item, &Vec::new(), Some(&tydef.type_), link.anchor(&id), "")?;
-                write!(w, "</code></h4>")?;
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_type(w, item, &Vec::new(), Some(&tydef.type_), link.anchor(&id), "");
+                write!(w, "</code></h4>");
             }
             clean::AssocConstItem(ref ty, ref default) => {
                 let id = cx.derive_id(format!("{}.{}", item_type, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "")?;
-                write!(w, "</code>")?;
-                render_stability_since_raw(w, item.stable_since(), outer_version)?;
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_const(w, item, ty, default.as_ref(), link.anchor(&id), "");
+                write!(w, "</code>");
+                render_stability_since_raw(w, item.stable_since(), outer_version);
                 if let Some(l) = cx.src_href(item) {
                     write!(w, "<a class='srclink' href='{}' title='{}'>[src]</a>",
-                            l, "goto source code")?;
+                            l, "goto source code");
                 }
-                write!(w, "</h4>")?;
+                write!(w, "</h4>");
             }
             clean::AssocTypeItem(ref bounds, ref default) => {
                 let id = cx.derive_id(format!("{}.{}", item_type, name));
                 let ns_id = cx.derive_id(format!("{}.{}", name, item_type.name_space()));
-                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class)?;
-                write!(w, "<code id='{}'>", ns_id)?;
-                assoc_type(w, item, bounds, default.as_ref(), link.anchor(&id), "")?;
-                write!(w, "</code></h4>")?;
+                write!(w, "<h4 id='{}' class=\"{}{}\">", id, item_type, extra_class);
+                write!(w, "<code id='{}'>", ns_id);
+                assoc_type(w, item, bounds, default.as_ref(), link.anchor(&id), "");
+                write!(w, "</code></h4>");
             }
-            clean::StrippedItem(..) => return Ok(()),
+            clean::StrippedItem(..) => return,
             _ => panic!("can't make docs for trait item with name {:?}", item.name)
         }
 
@@ -4094,47 +4049,46 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
                     if let Some(it) = t.items.iter().find(|i| i.name == item.name) {
                         // We need the stability of the item from the trait
                         // because impls can't have a stability.
-                        document_stability(w, cx, it, is_hidden)?;
+                        document_stability(w, cx, it, is_hidden);
                         if item.doc_value().is_some() {
-                            document_full(w, item, cx, "", is_hidden)?;
+                            document_full(w, item, cx, "", is_hidden);
                         } else if show_def_docs {
                             // In case the item isn't documented,
                             // provide short documentation from the trait.
-                            document_short(w, cx, it, link, "", is_hidden)?;
+                            document_short(w, cx, it, link, "", is_hidden);
                         }
                     }
                 } else {
-                    document_stability(w, cx, item, is_hidden)?;
+                    document_stability(w, cx, item, is_hidden);
                     if show_def_docs {
-                        document_full(w, item, cx, "", is_hidden)?;
+                        document_full(w, item, cx, "", is_hidden);
                     }
                 }
             } else {
-                document_stability(w, cx, item, is_hidden)?;
+                document_stability(w, cx, item, is_hidden);
                 if show_def_docs {
-                    document_short(w, cx, item, link, "", is_hidden)?;
+                    document_short(w, cx, item, link, "", is_hidden);
                 }
             }
         }
-        Ok(())
     }
 
     let traits = &cache().traits;
     let trait_ = i.trait_did().map(|did| &traits[&did]);
 
-    write!(w, "<div class='impl-items'>")?;
+    write!(w, "<div class='impl-items'>");
     for trait_item in &i.inner_impl().items {
         doc_impl_item(w, cx, trait_item, link, render_mode,
-                      false, outer_version, trait_, show_def_docs)?;
+                      false, outer_version, trait_, show_def_docs);
     }
 
-    fn render_default_items(w: &mut fmt::Formatter<'_>,
+    fn render_default_items(w: &mut Buffer,
                             cx: &Context,
                             t: &clean::Trait,
                             i: &clean::Impl,
                             render_mode: RenderMode,
                             outer_version: Option<&str>,
-                            show_def_docs: bool) -> fmt::Result {
+                            show_def_docs: bool) {
         for trait_item in &t.items {
             let n = trait_item.name.clone();
             if i.items.iter().find(|m| m.name == n).is_some() {
@@ -4144,9 +4098,8 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
             let assoc_link = AssocItemLink::GotoSource(did, &i.provided_trait_methods);
 
             doc_impl_item(w, cx, trait_item, assoc_link, render_mode, true,
-                          outer_version, None, show_def_docs)?;
+                          outer_version, None, show_def_docs);
         }
-        Ok(())
     }
 
     // If we've implemented a trait, then also emit documentation for all
@@ -4156,29 +4109,27 @@ fn render_impl(w: &mut fmt::Formatter<'_>, cx: &Context, i: &Impl, link: AssocIt
     if show_default_items {
         if let Some(t) = trait_ {
             render_default_items(w, cx, t, &i.inner_impl(),
-                                render_mode, outer_version, show_def_docs)?;
+                                render_mode, outer_version, show_def_docs);
         }
     }
-    write!(w, "</div>")?;
-
-    Ok(())
+    write!(w, "</div>");
 }
 
 fn item_opaque_ty(
-    w: &mut fmt::Formatter<'_>,
+    w: &mut Buffer,
     cx: &Context,
     it: &clean::Item,
     t: &clean::OpaqueTy,
-) -> fmt::Result {
-    write!(w, "<pre class='rust opaque'>")?;
-    render_attributes(w, it, false)?;
+) {
+    write!(w, "<pre class='rust opaque'>");
+    render_attributes(w, it, false);
     write!(w, "type {}{}{where_clause} = impl {bounds};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            where_clause = WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           bounds = bounds(&t.bounds, false))?;
+           bounds = bounds(&t.bounds, false));
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4187,17 +4138,17 @@ fn item_opaque_ty(
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_trait_alias(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                    t: &clean::TraitAlias) -> fmt::Result {
-    write!(w, "<pre class='rust trait-alias'>")?;
-    render_attributes(w, it, false)?;
+fn item_trait_alias(w: &mut Buffer, cx: &Context, it: &clean::Item,
+                    t: &clean::TraitAlias) {
+    write!(w, "<pre class='rust trait-alias'>");
+    render_attributes(w, it, false);
     write!(w, "trait {}{}{} = {};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           bounds(&t.bounds, true))?;
+           bounds(&t.bounds, true));
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4206,17 +4157,16 @@ fn item_trait_alias(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_typedef(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-                t: &clean::Typedef) -> fmt::Result {
-    write!(w, "<pre class='rust typedef'>")?;
-    render_attributes(w, it, false)?;
+fn item_typedef(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Typedef) {
+    write!(w, "<pre class='rust typedef'>");
+    render_attributes(w, it, false);
     write!(w, "type {}{}{where_clause} = {type_};</pre>",
            it.name.as_ref().unwrap(),
            t.generics,
            where_clause = WhereClause { gens: &t.generics, indent: 0, end_newline: true },
-           type_ = t.type_)?;
+           type_ = t.type_);
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
@@ -4225,17 +4175,17 @@ fn item_typedef(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_foreign_type(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item) -> fmt::Result {
-    writeln!(w, "<pre class='rust foreigntype'>extern {{")?;
-    render_attributes(w, it, false)?;
+fn item_foreign_type(w: &mut Buffer, cx: &Context, it: &clean::Item) {
+    writeln!(w, "<pre class='rust foreigntype'>extern {{");
+    render_attributes(w, it, false);
     write!(
         w,
         "    {}type {};\n}}</pre>",
         VisSpace(&it.visibility),
         it.name.as_ref().unwrap(),
-    )?;
+    );
 
-    document(w, cx, it)?;
+    document(w, cx, it);
 
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
@@ -4790,59 +4740,56 @@ fn sidebar_foreign_type(buf: &mut Buffer, it: &clean::Item) {
     }
 }
 
-fn item_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
-              t: &clean::Macro) -> fmt::Result {
+fn item_macro(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Macro) {
     wrap_into_docblock(w, |w| {
         w.write_str(&highlight::render_with_highlighting(&t.source,
                                                          Some("macro"),
                                                          None,
                                                          None))
-    })?;
+    });
     document(w, cx, it)
 }
 
-fn item_proc_macro(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item, m: &clean::ProcMacro)
-    -> fmt::Result
-{
+fn item_proc_macro(w: &mut Buffer, cx: &Context, it: &clean::Item, m: &clean::ProcMacro) {
     let name = it.name.as_ref().expect("proc-macros always have names");
     match m.kind {
         MacroKind::Bang => {
-            write!(w, "<pre class='rust macro'>")?;
-            write!(w, "{}!() {{ /* proc-macro */ }}", name)?;
-            write!(w, "</pre>")?;
+            write!(w, "<pre class='rust macro'>");
+            write!(w, "{}!() {{ /* proc-macro */ }}", name);
+            write!(w, "</pre>");
         }
         MacroKind::Attr => {
-            write!(w, "<pre class='rust attr'>")?;
-            write!(w, "#[{}]", name)?;
-            write!(w, "</pre>")?;
+            write!(w, "<pre class='rust attr'>");
+            write!(w, "#[{}]", name);
+            write!(w, "</pre>");
         }
         MacroKind::Derive => {
-            write!(w, "<pre class='rust derive'>")?;
-            write!(w, "#[derive({})]", name)?;
+            write!(w, "<pre class='rust derive'>");
+            write!(w, "#[derive({})]", name);
             if !m.helpers.is_empty() {
-                writeln!(w, "\n{{")?;
-                writeln!(w, "    // Attributes available to this derive:")?;
+                writeln!(w, "\n{{");
+                writeln!(w, "    // Attributes available to this derive:");
                 for attr in &m.helpers {
-                    writeln!(w, "    #[{}]", attr)?;
+                    writeln!(w, "    #[{}]", attr);
                 }
-                write!(w, "}}")?;
+                write!(w, "}}");
             }
-            write!(w, "</pre>")?;
+            write!(w, "</pre>");
         }
     }
     document(w, cx, it)
 }
 
-fn item_primitive(w: &mut fmt::Formatter<'_>, cx: &Context,
+fn item_primitive(w: &mut Buffer, cx: &Context,
                   it: &clean::Item,
-                  _p: &clean::PrimitiveType) -> fmt::Result {
-    document(w, cx, it)?;
+                  _p: &clean::PrimitiveType) {
+    document(w, cx, it);
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All)
 }
 
-fn item_keyword(w: &mut fmt::Formatter<'_>, cx: &Context,
+fn item_keyword(w: &mut Buffer, cx: &Context,
                 it: &clean::Item,
-                _p: &str) -> fmt::Result {
+                _p: &str) {
     document(w, cx, it)
 }
 

From dd323f8a72327aba0b4771ea08a8b007bba995ca Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Mon, 2 Sep 2019 17:28:37 -0400
Subject: [PATCH 33/33] Emit error on intrinsic to fn ptr casts

---
 src/librustc/infer/error_reporting/mod.rs |  3 +++
 src/librustc/ty/error.rs                  |  5 +++++
 src/librustc/ty/structural_impls.rs       |  2 ++
 src/librustc_typeck/check/cast.rs         |  4 ++++
 src/librustc_typeck/check/coercion.rs     |  6 ++++++
 src/test/ui/reify-intrinsic.rs            | 15 +++++++++++++++
 src/test/ui/reify-intrinsic.stderr        | 22 ++++++++++++++++++++++
 7 files changed, 57 insertions(+)
 create mode 100644 src/test/ui/reify-intrinsic.rs
 create mode 100644 src/test/ui/reify-intrinsic.stderr

diff --git a/src/librustc/infer/error_reporting/mod.rs b/src/librustc/infer/error_reporting/mod.rs
index 9be73cf3c6d16..e684ccfeeb7ed 100644
--- a/src/librustc/infer/error_reporting/mod.rs
+++ b/src/librustc/infer/error_reporting/mod.rs
@@ -1636,6 +1636,9 @@ impl<'tcx> ObligationCause<'tcx> {
                 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
                     Error0644("closure/generator type that references itself")
                 }
+                TypeError::IntrinsicCast => {
+                    Error0308("cannot coerce intrinsics to function pointers")
+                }
                 _ => Error0308("mismatched types"),
             },
         }
diff --git a/src/librustc/ty/error.rs b/src/librustc/ty/error.rs
index c70006b68d69a..fe8f94ab1d314 100644
--- a/src/librustc/ty/error.rs
+++ b/src/librustc/ty/error.rs
@@ -46,6 +46,8 @@ pub enum TypeError<'tcx> {
     ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
 
     ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>),
+
+    IntrinsicCast,
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
@@ -179,6 +181,9 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             ConstMismatch(ref values) => {
                 write!(f, "expected `{}`, found `{}`", values.expected, values.found)
             }
+            IntrinsicCast => {
+                write!(f, "cannot coerce intrinsics to function pointers")
+            }
         }
     }
 }
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index 649a5244728ba..ec7cf1a13c596 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -748,6 +748,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
             Sorts(ref x) => return tcx.lift(x).map(Sorts),
             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
+            IntrinsicCast => IntrinsicCast,
         })
     }
 }
@@ -1338,6 +1339,7 @@ EnumTypeFoldableImpl! {
         (ty::error::TypeError::Sorts)(x),
         (ty::error::TypeError::ExistentialMismatch)(x),
         (ty::error::TypeError::ConstMismatch)(x),
+        (ty::error::TypeError::IntrinsicCast),
     }
 }
 
diff --git a/src/librustc_typeck/check/cast.rs b/src/librustc_typeck/check/cast.rs
index 55e7a10f1aaa4..c216cc92b1e58 100644
--- a/src/librustc_typeck/check/cast.rs
+++ b/src/librustc_typeck/check/cast.rs
@@ -40,6 +40,7 @@ use rustc::ty::{self, Ty, TypeFoldable, TypeAndMut};
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::adjustment::AllowTwoPhase;
 use rustc::ty::cast::{CastKind, CastTy};
+use rustc::ty::error::TypeError;
 use rustc::middle::lang_items;
 use syntax::ast;
 use syntax_pos::Span;
@@ -461,6 +462,9 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                                              self.expr_ty,
                                              fcx.tcx.mk_fn_ptr(f),
                                              AllowTwoPhase::No);
+                    if let Err(TypeError::IntrinsicCast) = res {
+                        return Err(CastError::IllegalCast);
+                    }
                     if res.is_err() {
                         return Err(CastError::NonScalar);
                     }
diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs
index 61b9c2a15ba16..f2e1a6e29d6fc 100644
--- a/src/librustc_typeck/check/coercion.rs
+++ b/src/librustc_typeck/check/coercion.rs
@@ -70,6 +70,7 @@ use std::ops::Deref;
 use syntax::feature_gate;
 use syntax::symbol::sym;
 use syntax_pos;
+use rustc_target::spec::abi::Abi;
 
 struct Coerce<'a, 'tcx> {
     fcx: &'a FnCtxt<'a, 'tcx>,
@@ -689,6 +690,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         match b.sty {
             ty::FnPtr(_) => {
                 let a_sig = a.fn_sig(self.tcx);
+                // Intrinsics are not coercible to function pointers
+                if a_sig.abi() == Abi::RustIntrinsic ||
+                   a_sig.abi() == Abi::PlatformIntrinsic {
+                   return Err(TypeError::IntrinsicCast);
+                }
                 let InferOk { value: a_sig, mut obligations } =
                     self.normalize_associated_types_in_as_infer_ok(self.cause.span, &a_sig);
 
diff --git a/src/test/ui/reify-intrinsic.rs b/src/test/ui/reify-intrinsic.rs
new file mode 100644
index 0000000000000..09baa059e5567
--- /dev/null
+++ b/src/test/ui/reify-intrinsic.rs
@@ -0,0 +1,15 @@
+// check-fail
+
+#![feature(intrinsics)]
+
+fn a() {
+    let _: unsafe extern "rust-intrinsic" fn(isize) -> usize = std::mem::transmute;
+    //~^ ERROR cannot coerce
+}
+
+fn b() {
+    let _ = std::mem::transmute as unsafe extern "rust-intrinsic" fn(isize) -> usize;
+    //~^ ERROR casting
+}
+
+fn main() {}
diff --git a/src/test/ui/reify-intrinsic.stderr b/src/test/ui/reify-intrinsic.stderr
new file mode 100644
index 0000000000000..4a1bd77cf7ee9
--- /dev/null
+++ b/src/test/ui/reify-intrinsic.stderr
@@ -0,0 +1,22 @@
+error[E0308]: cannot coerce intrinsics to function pointers
+  --> $DIR/reify-intrinsic.rs:6:64
+   |
+LL |     let _: unsafe extern "rust-intrinsic" fn(isize) -> usize = std::mem::transmute;
+   |                                                                ^^^^^^^^^^^^^^^^^^^
+   |                                                                |
+   |                                                                cannot coerce intrinsics to function pointers
+   |                                                                help: use parentheses to call this function: `std::mem::transmute(...)`
+   |
+   = note: expected type `unsafe extern "rust-intrinsic" fn(isize) -> usize`
+              found type `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
+
+error[E0606]: casting `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}` as `unsafe extern "rust-intrinsic" fn(isize) -> usize` is invalid
+  --> $DIR/reify-intrinsic.rs:11:13
+   |
+LL |     let _ = std::mem::transmute as unsafe extern "rust-intrinsic" fn(isize) -> usize;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0308, E0606.
+For more information about an error, try `rustc --explain E0308`.