Rollup of 8 pull requests

compiler/rustc_errors/src/emitter.rs

@@ -195,6 +195,9 @@ pub trait Emitter {
 
     fn emit_future_breakage_report(&mut self, _diags: Vec<(FutureBreakage, Diagnostic)>) {}
 
+    /// Emit list of unused externs
+    fn emit_unused_externs(&mut self, _lint_level: &str, _unused_externs: &[&str]) {}
+
     /// Checks if should show explanations about "rustc --explain"
     fn should_show_explain(&self) -> bool {
         true

compiler/rustc_errors/src/json.rs

@@ -159,6 +159,19 @@ impl Emitter for JsonEmitter {
         }
     }
 
+    fn emit_unused_externs(&mut self, lint_level: &str, unused_externs: &[&str]) {
+        let data = UnusedExterns { lint_level, unused_extern_names: unused_externs };
+        let result = if self.pretty {
+            writeln!(&mut self.dst, "{}", as_pretty_json(&data))
+        } else {
+            writeln!(&mut self.dst, "{}", as_json(&data))
+        }
+        .and_then(|_| self.dst.flush());
+        if let Err(e) = result {
+            panic!("failed to print unused externs: {:?}", e);
+        }
+    }
+
     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
         Some(&self.sm)
     }
@@ -322,6 +335,18 @@ struct FutureIncompatReport {
     future_incompat_report: Vec<FutureBreakageItem>,
 }
 
+// NOTE: Keep this in sync with the equivalent structs in rustdoc's
+// doctest component (as well as cargo).
+// We could unify this struct the one in rustdoc but they have different
+// ownership semantics, so doing so would create wasteful allocations.
+#[derive(Encodable)]
+struct UnusedExterns<'a, 'b, 'c> {
+    /// The severity level of the unused dependencies lint
+    lint_level: &'a str,
+    /// List of unused externs by their names.
+    unused_extern_names: &'b [&'c str],
+}
+
 impl Diagnostic {
     fn from_errors_diagnostic(diag: &crate::Diagnostic, je: &JsonEmitter) -> Diagnostic {
         let sugg = diag.suggestions.iter().map(|sugg| Diagnostic {

compiler/rustc_errors/src/lib.rs

@@ -765,6 +765,10 @@ impl Handler {
         self.inner.borrow_mut().emitter.emit_future_breakage_report(diags)
     }
 
+    pub fn emit_unused_externs(&self, lint_level: &str, unused_externs: &[&str]) {
+        self.inner.borrow_mut().emit_unused_externs(lint_level, unused_externs)
+    }
+
     pub fn delay_as_bug(&self, diagnostic: Diagnostic) {
         self.inner.borrow_mut().delay_as_bug(diagnostic)
     }
@@ -839,6 +843,10 @@ impl HandlerInner {
         self.emitter.emit_artifact_notification(path, artifact_type);
     }
 
+    fn emit_unused_externs(&mut self, lint_level: &str, unused_externs: &[&str]) {
+        self.emitter.emit_unused_externs(lint_level, unused_externs);
+    }
+
     fn treat_err_as_bug(&self) -> bool {
         self.flags.treat_err_as_bug.map_or(false, |c| self.err_count() >= c.get())
     }

compiler/rustc_interface/src/passes.rs

@@ -16,6 +16,7 @@ use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_hir::definitions::Definitions;
 use rustc_hir::Crate;
 use rustc_lint::LintStore;
+use rustc_metadata::creader::CStore;
 use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepGraph;
 use rustc_middle::middle;
@@ -831,6 +832,12 @@ fn analysis(tcx: TyCtxt<'_>, cnum: CrateNum) -> Result<()> {
                 });
 
                 sess.time("looking_for_derive_registrar", || proc_macro_decls::find(tcx));
+
+                let cstore = tcx
+                    .cstore_as_any()
+                    .downcast_ref::<CStore>()
+                    .expect("`tcx.cstore` is not a `CStore`");
+                cstore.report_unused_deps(tcx);
             },
             {
                 par_iter(&tcx.hir().krate().modules).for_each(|(&module, _)| {

compiler/rustc_metadata/src/creader.rs

@@ -46,6 +46,9 @@ pub struct CStore {
     /// This map is used to verify we get no hash conflicts between
     /// `StableCrateId` values.
     stable_crate_ids: FxHashMap<StableCrateId, CrateNum>,
+
+    /// Unused externs of the crate
+    unused_externs: Vec<Symbol>,
 }
 
 pub struct CrateLoader<'a> {
@@ -190,6 +193,27 @@ impl CStore {
     crate fn has_global_allocator(&self) -> bool {
         self.has_global_allocator
     }
+
+    pub fn report_unused_deps(&self, tcx: TyCtxt<'_>) {
+        // We put the check for the option before the lint_level_at_node call
+        // because the call mutates internal state and introducing it
+        // leads to some ui tests failing.
+        if !tcx.sess.opts.json_unused_externs {
+            return;
+        }
+        let level = tcx
+            .lint_level_at_node(lint::builtin::UNUSED_CRATE_DEPENDENCIES, rustc_hir::CRATE_HIR_ID)
+            .0;
+        if level != lint::Level::Allow {
+            let unused_externs =
+                self.unused_externs.iter().map(|ident| ident.to_ident_string()).collect::<Vec<_>>();
+            let unused_externs = unused_externs.iter().map(String::as_str).collect::<Vec<&str>>();
+            tcx.sess
+                .parse_sess
+                .span_diagnostic
+                .emit_unused_externs(level.as_str(), &unused_externs);
+        }
+    }
 }
 
 impl<'a> CrateLoader<'a> {
@@ -217,6 +241,7 @@ impl<'a> CrateLoader<'a> {
                 allocator_kind: None,
                 has_global_allocator: false,
                 stable_crate_ids,
+                unused_externs: Vec::new(),
             },
             used_extern_options: Default::default(),
         }
@@ -904,11 +929,17 @@ impl<'a> CrateLoader<'a> {
                 // Don't worry about pathless `--extern foo` sysroot references
                 continue;
             }
-            if self.used_extern_options.contains(&Symbol::intern(name)) {
+            let name_interned = Symbol::intern(name);
+            if self.used_extern_options.contains(&name_interned) {
                 continue;
             }
 
             // Got a real unused --extern
+            if self.sess.opts.json_unused_externs {
+                self.cstore.unused_externs.push(name_interned);
+                continue;
+            }
+
             let diag = match self.sess.opts.extern_dep_specs.get(name) {
                 Some(loc) => BuiltinLintDiagnostics::ExternDepSpec(name.clone(), loc.into()),
                 None => {
@@ -941,9 +972,9 @@ impl<'a> CrateLoader<'a> {
         self.inject_allocator_crate(krate);
         self.inject_panic_runtime(krate);
 
-        info!("{:?}", CrateDump(&self.cstore));
-
         self.report_unused_deps(krate);
+
+        info!("{:?}", CrateDump(&self.cstore));
     }
 
     pub fn process_extern_crate(

compiler/rustc_middle/src/mir/mod.rs

@@ -1482,7 +1482,7 @@ pub enum StatementKind<'tcx> {
     ///
     /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
     /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
-    FakeRead(FakeReadCause, Box<Place<'tcx>>),
+    FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
 
     /// Write the discriminant for a variant to the enum Place.
     SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
@@ -1575,7 +1575,12 @@ pub enum FakeReadCause {
 
     /// `let x: !; match x {}` doesn't generate any read of x so we need to
     /// generate a read of x to check that it is initialized and safe.
-    ForMatchedPlace,
+    ///
+    /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
+    /// FakeRead for that Place outside the closure, in such a case this option would be
+    /// Some(closure_def_id).
+    /// Otherwise, the value of the optional DefId will be None.
+    ForMatchedPlace(Option<DefId>),
 
     /// A fake read of the RefWithinGuard version of a bind-by-value variable
     /// in a match guard to ensure that it's value hasn't change by the time
@@ -1594,7 +1599,12 @@ pub enum FakeReadCause {
     /// but in some cases it can affect the borrow checker, as in #53695.
     /// Therefore, we insert a "fake read" here to ensure that we get
     /// appropriate errors.
-    ForLet,
+    ///
+    /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
+    /// FakeRead for that Place outside the closure, in such a case this option would be
+    /// Some(closure_def_id).
+    /// Otherwise, the value of the optional DefId will be None.
+    ForLet(Option<DefId>),
 
     /// If we have an index expression like
     ///
@@ -1618,7 +1628,9 @@ impl Debug for Statement<'_> {
         use self::StatementKind::*;
         match self.kind {
             Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
-            FakeRead(ref cause, ref place) => write!(fmt, "FakeRead({:?}, {:?})", cause, place),
+            FakeRead(box (ref cause, ref place)) => {
+                write!(fmt, "FakeRead({:?}, {:?})", cause, place)
+            }
             Retag(ref kind, ref place) => write!(
                 fmt,
                 "Retag({}{:?})",

compiler/rustc_middle/src/mir/visit.rs

@@ -380,7 +380,7 @@ macro_rules! make_mir_visitor {
                     ) => {
                         self.visit_assign(place, rvalue, location);
                     }
-                    StatementKind::FakeRead(_, place) => {
+                    StatementKind::FakeRead(box (_, place)) => {
                         self.visit_place(
                             place,
                             PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect),

compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs

@@ -1728,7 +1728,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         impl<'tcx> Visitor<'tcx> for FakeReadCauseFinder<'tcx> {
             fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) {
                 match statement {
-                    Statement { kind: StatementKind::FakeRead(cause, box place), .. }
+                    Statement { kind: StatementKind::FakeRead(box (cause, place)), .. }
                         if *place == self.place =>
                     {
                         self.cause = Some(*cause);

compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs

@@ -515,7 +515,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 let block = &self.body.basic_blocks()[location.block];
 
                 let kind = if let Some(&Statement {
-                    kind: StatementKind::FakeRead(FakeReadCause::ForLet, _),
+                    kind: StatementKind::FakeRead(box (FakeReadCause::ForLet(_), _)),
                     ..
                 }) = block.statements.get(location.statement_index)
                 {

compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs

@@ -7,8 +7,8 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItemGroup;
 use rustc_hir::GeneratorKind;
 use rustc_middle::mir::{
-    AggregateKind, Constant, Field, Local, LocalInfo, LocalKind, Location, Operand, Place,
-    PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
+    AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
+    Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
 };
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
@@ -795,6 +795,24 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
         }
 
+        // StatementKind::FakeRead only contains a def_id if they are introduced as a result
+        // of pattern matching within a closure.
+        if let StatementKind::FakeRead(box (cause, ref place)) = stmt.kind {
+            match cause {
+                FakeReadCause::ForMatchedPlace(Some(closure_def_id))
+                | FakeReadCause::ForLet(Some(closure_def_id)) => {
+                    debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
+                    let places = &[Operand::Move(*place)];
+                    if let Some((args_span, generator_kind, var_span)) =
+                        self.closure_span(closure_def_id, moved_place, places)
+                    {
+                        return ClosureUse { generator_kind, args_span, var_span };
+                    }
+                }
+                _ => {}
+            }
+        }
+
         let normal_ret =
             if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
                 PatUse(stmt.source_info.span)

compiler/rustc_mir/src/borrow_check/invalidation.rs

@@ -63,7 +63,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
 
                 self.mutate_place(location, *lhs, Shallow(None), JustWrite);
             }
-            StatementKind::FakeRead(_, _) => {
+            StatementKind::FakeRead(box (_, _)) => {
                 // Only relevant for initialized/liveness/safety checks.
             }
             StatementKind::SetDiscriminant { place, variant_index: _ } => {

compiler/rustc_mir/src/borrow_check/mod.rs

@@ -574,7 +574,7 @@ impl<'cx, 'tcx> dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tc
 
                 self.mutate_place(location, (*lhs, span), Shallow(None), JustWrite, flow_state);
             }
-            StatementKind::FakeRead(_, box ref place) => {
+            StatementKind::FakeRead(box (_, ref place)) => {
                 // Read for match doesn't access any memory and is used to
                 // assert that a place is safe and live. So we don't have to
                 // do any checks here.

compiler/rustc_mir/src/dataflow/move_paths/builder.rs

@@ -293,8 +293,8 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                 }
                 self.gather_rvalue(rval);
             }
-            StatementKind::FakeRead(_, place) => {
-                self.create_move_path(**place);
+            StatementKind::FakeRead(box (_, place)) => {
+                self.create_move_path(*place);
             }
             StatementKind::LlvmInlineAsm(ref asm) => {
                 for (output, kind) in iter::zip(&*asm.outputs, &asm.asm.outputs) {

compiler/rustc_mir/src/transform/coverage/spans.rs

@@ -683,10 +683,10 @@ pub(super) fn filtered_statement_span(
         // and `_1` is the `Place` for `somenum`.
         //
         // If and when the Issue is resolved, remove this special case match pattern:
-        StatementKind::FakeRead(cause, _) if cause == FakeReadCause::ForGuardBinding => None,
+        StatementKind::FakeRead(box (cause, _)) if cause == FakeReadCause::ForGuardBinding => None,
 
         // Retain spans from all other statements
-        StatementKind::FakeRead(_, _) // Not including `ForGuardBinding`
+        StatementKind::FakeRead(box (_, _)) // Not including `ForGuardBinding`
         | StatementKind::CopyNonOverlapping(..)
         | StatementKind::Assign(_)
         | StatementKind::SetDiscriminant { .. }

compiler/rustc_mir_build/src/build/cfg.rs

@@ -80,7 +80,7 @@ impl<'tcx> CFG<'tcx> {
         cause: FakeReadCause,
         place: Place<'tcx>,
     ) {
-        let kind = StatementKind::FakeRead(cause, box place);
+        let kind = StatementKind::FakeRead(box (cause, place));
         let stmt = Statement { source_info, kind };
         self.push(block, stmt);
     }

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -179,24 +179,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 //     match x { _ => () } // fake read of `x`
                 // };
                 // ```
-                // FIXME(RFC2229): Remove feature gate once diagnostics are improved
-                if this.tcx.features().capture_disjoint_fields {
-                    for (thir_place, cause, hir_id) in fake_reads.into_iter() {
-                        let place_builder =
-                            unpack!(block = this.as_place_builder(block, thir_place));
-
-                        if let Ok(place_builder_resolved) =
-                            place_builder.try_upvars_resolved(this.tcx, this.typeck_results)
-                        {
-                            let mir_place =
-                                place_builder_resolved.into_place(this.tcx, this.typeck_results);
-                            this.cfg.push_fake_read(
-                                block,
-                                this.source_info(this.tcx.hir().span(*hir_id)),
-                                *cause,
-                                mir_place,
-                            );
-                        }
+                for (thir_place, cause, hir_id) in fake_reads.into_iter() {
+                    let place_builder = unpack!(block = this.as_place_builder(block, thir_place));
+
+                    if let Ok(place_builder_resolved) =
+                        place_builder.try_upvars_resolved(this.tcx, this.typeck_results)
+                    {
+                        let mir_place =
+                            place_builder_resolved.into_place(this.tcx, this.typeck_results);
+                        this.cfg.push_fake_read(
+                            block,
+                            this.source_info(this.tcx.hir().span(*hir_id)),
+                            *cause,
+                            mir_place,
+                        );
                     }
                 }
 

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -139,7 +139,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // uninhabited value. If we get never patterns, those will check that
         // the place is initialized, and so this read would only be used to
         // check safety.
-        let cause_matched_place = FakeReadCause::ForMatchedPlace;
+        let cause_matched_place = FakeReadCause::ForMatchedPlace(None);
         let source_info = self.source_info(scrutinee_span);
 
         if let Ok(scrutinee_builder) =
@@ -400,7 +400,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                 // Inject a fake read, see comments on `FakeReadCause::ForLet`.
                 let source_info = self.source_info(irrefutable_pat.span);
-                self.cfg.push_fake_read(block, source_info, FakeReadCause::ForLet, place);
+                self.cfg.push_fake_read(block, source_info, FakeReadCause::ForLet(None), place);
 
                 self.schedule_drop_for_binding(var, irrefutable_pat.span, OutsideGuard);
                 block.unit()
@@ -435,7 +435,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                 // Inject a fake read, see comments on `FakeReadCause::ForLet`.
                 let pattern_source_info = self.source_info(irrefutable_pat.span);
-                let cause_let = FakeReadCause::ForLet;
+                let cause_let = FakeReadCause::ForLet(None);
                 self.cfg.push_fake_read(block, pattern_source_info, cause_let, place);
 
                 let ty_source_info = self.source_info(user_ty_span);