rescope temp lifetime in let-chain into IfElse

rust-lang · Apr 25, 2024 · 3d420e9 · 3d420e9
1 parent b9be3c4
commit 3d420e9
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Showing 23 changed files with 253 additions and 65 deletions.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
@@ -495,6 +495,8 @@ declare_features! (
     (unstable, half_open_range_patterns_in_slices, "1.66.0", Some(67264)),
     /// Allows `if let` guard in match arms.
     (unstable, if_let_guard, "1.47.0", Some(51114)),
+    /// Rescoping temporaries in `if let` to align with Rust 2024.
+    (unstable, if_let_rescope, "1.78.0", Some(124085)),
     /// Allows `impl Trait` to be used inside associated types (RFC 2515).
     (unstable, impl_trait_in_assoc_type, "1.70.0", Some(63063)),
     /// Allows `impl Trait` as output type in `Fn` traits in return position of functions.

diff --git a/compiler/rustc_hir_typeck/src/rvalue_scopes.rs b/compiler/rustc_hir_typeck/src/rvalue_scopes.rs
@@ -69,7 +69,8 @@ pub fn resolve_rvalue_scopes<'a, 'tcx>(
     def_id: DefId,
 ) -> RvalueScopes {
     let tcx = &fcx.tcx;
-    let mut rvalue_scopes = RvalueScopes::new();
+    let mut rvalue_scopes =
+        RvalueScopes::new(tcx.features().if_let_rescope && tcx.sess.at_least_rust_2024());
     debug!("start resolving rvalue scopes, def_id={def_id:?}");
     debug!("rvalue_scope: rvalue_candidates={:?}", scope_tree.rvalue_candidates);
     for (&hir_id, candidate) in &scope_tree.rvalue_candidates {

diff --git a/compiler/rustc_middle/src/ty/rvalue_scopes.rs b/compiler/rustc_middle/src/ty/rvalue_scopes.rs
@@ -6,12 +6,13 @@ use rustc_hir::ItemLocalMap;
 /// rules laid out in `rustc_hir_analysis::check::rvalue_scopes`.
 #[derive(TyEncodable, TyDecodable, Clone, Debug, Default, Eq, PartialEq, HashStable)]
 pub struct RvalueScopes {
+    rescope_if_let: bool,
     map: ItemLocalMap<Option<Scope>>,
 }
 
 impl RvalueScopes {
-    pub fn new() -> Self {
-        Self { map: <_>::default() }
+    pub fn new(rescope_if_let: bool) -> Self {
+        Self { rescope_if_let, map: <_>::default() }
     }
 
     /// Returns the scope when the temp created by `expr_id` will be cleaned up.
@@ -38,7 +39,17 @@ impl RvalueScopes {
                     debug!("temporary_scope({expr_id:?}) = {id:?} [enclosing]");
                     return Some(id);
                 }
-                _ => id = p,
+                ScopeData::IfThen => {
+                    if self.rescope_if_let {
+                        debug!("temporary_scope({expr_id:?}) = {p:?} [enclosing]");
+                        return Some(p);
+                    }
+                    id = p;
+                }
+                ScopeData::Node
+                | ScopeData::CallSite
+                | ScopeData::Arguments
+                | ScopeData::Remainder(_) => id = p,
             }
         }
 

diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -964,6 +964,7 @@ symbols! {
         ident,
         if_let,
         if_let_guard,
+        if_let_rescope,
         if_while_or_patterns,
         ignore,
         impl_header_lifetime_elision,

diff --git a/tests/mir-opt/building/logical_or_in_conditional.test_complex.built.after.mir b/tests/mir-opt/building/logical_or_in_conditional.test_complex.built.after.mir
@@ -19,7 +19,7 @@ fn test_complex() -> () {
     bb0: {
         StorageLive(_1);
         StorageLive(_2);
-        _2 = E::f() -> [return: bb1, unwind: bb38];
+        _2 = E::f() -> [return: bb1, unwind: bb39];
     }
 
     bb1: {
@@ -51,7 +51,7 @@ fn test_complex() -> () {
 
     bb7: {
         StorageLive(_4);
-        _4 = always_true() -> [return: bb8, unwind: bb38];
+        _4 = always_true() -> [return: bb8, unwind: bb39];
     }
 
     bb8: {
@@ -73,7 +73,7 @@ fn test_complex() -> () {
     }
 
     bb11: {
-        drop(_7) -> [return: bb13, unwind: bb38];
+        drop(_7) -> [return: bb13, unwind: bb39];
     }
 
     bb12: {
@@ -87,7 +87,7 @@ fn test_complex() -> () {
     }
 
     bb14: {
-        drop(_7) -> [return: bb15, unwind: bb38];
+        drop(_7) -> [return: bb15, unwind: bb39];
     }
 
     bb15: {
@@ -107,7 +107,7 @@ fn test_complex() -> () {
     }
 
     bb17: {
-        drop(_10) -> [return: bb19, unwind: bb38];
+        drop(_10) -> [return: bb19, unwind: bb39];
     }
 
     bb18: {
@@ -122,11 +122,12 @@ fn test_complex() -> () {
 
     bb20: {
         _1 = const ();
+        StorageDead(_2);
         goto -> bb24;
     }
 
     bb21: {
-        drop(_10) -> [return: bb22, unwind: bb38];
+        drop(_10) -> [return: bb22, unwind: bb39];
     }
 
     bb22: {
@@ -136,6 +137,7 @@ fn test_complex() -> () {
     }
 
     bb23: {
+        StorageDead(_2);
         _1 = const ();
         goto -> bb24;
     }
@@ -144,18 +146,17 @@ fn test_complex() -> () {
         StorageDead(_8);
         StorageDead(_5);
         StorageDead(_4);
-        StorageDead(_2);
         StorageDead(_1);
         StorageLive(_11);
-        _11 = always_true() -> [return: bb25, unwind: bb38];
+        _11 = always_true() -> [return: bb25, unwind: bb39];
     }
 
     bb25: {
         switchInt(move _11) -> [0: bb27, otherwise: bb26];
     }
 
     bb26: {
-        goto -> bb36;
+        goto -> bb37;
     }
 
     bb27: {
@@ -164,7 +165,7 @@ fn test_complex() -> () {
 
     bb28: {
         StorageLive(_12);
-        _12 = E::f() -> [return: bb29, unwind: bb38];
+        _12 = E::f() -> [return: bb29, unwind: bb39];
     }
 
     bb29: {
@@ -196,21 +197,26 @@ fn test_complex() -> () {
 
     bb35: {
         _0 = const ();
-        goto -> bb37;
+        StorageDead(_12);
+        goto -> bb38;
     }
 
     bb36: {
-        _0 = const ();
+        StorageDead(_12);
         goto -> bb37;
     }
 
     bb37: {
+        _0 = const ();
+        goto -> bb38;
+    }
+
+    bb38: {
         StorageDead(_11);
-        StorageDead(_12);
         return;
     }
 
-    bb38 (cleanup): {
+    bb39 (cleanup): {
         resume;
     }
 }
diff --git a/tests/mir-opt/const_prop/discriminant.main.GVN.32bit.diff b/tests/mir-opt/const_prop/discriminant.main.GVN.32bit.diff
@@ -32,18 +32,19 @@
 
       bb2: {
           _2 = const 42_i32;
+          StorageDead(_3);
           goto -> bb4;
       }
 
       bb3: {
+          StorageDead(_3);
           _2 = const 10_i32;
           goto -> bb4;
       }
 
       bb4: {
           _1 = Add(move _2, const 0_i32);
           StorageDead(_2);
-          StorageDead(_3);
           _0 = const ();
           StorageDead(_1);
           return;

diff --git a/tests/mir-opt/const_prop/discriminant.main.GVN.64bit.diff b/tests/mir-opt/const_prop/discriminant.main.GVN.64bit.diff
@@ -32,18 +32,19 @@
 
       bb2: {
           _2 = const 42_i32;
+          StorageDead(_3);
           goto -> bb4;
       }
 
       bb3: {
+          StorageDead(_3);
           _2 = const 10_i32;
           goto -> bb4;
       }
 
       bb4: {
           _1 = Add(move _2, const 0_i32);
           StorageDead(_2);
-          StorageDead(_3);
           _0 = const ();
           StorageDead(_1);
           return;

diff --git a/tests/mir-opt/const_prop/while_let_loops.change_loop_body.GVN.diff b/tests/mir-opt/const_prop/while_let_loops.change_loop_body.GVN.diff
@@ -37,18 +37,19 @@
       bb2: {
           _1 = const 1_i32;
           _0 = const ();
+          StorageDead(_3);
           goto -> bb4;
       }
 
       bb3: {
+          StorageDead(_3);
           StorageLive(_7);
           _0 = const ();
           StorageDead(_7);
           goto -> bb4;
       }
 
       bb4: {
-          StorageDead(_3);
           StorageDead(_1);
           return;
       }

diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-abort.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-abort.diff
@@ -103,10 +103,12 @@
           StorageDead(_9);
 -         StorageDead(_8);
 +         nop;
+          StorageDead(_6);
           goto -> bb8;
       }
 
       bb6: {
+          StorageDead(_6);
           StorageLive(_16);
           _16 = _1;
           StorageLive(_17);
@@ -130,7 +132,6 @@
       bb8: {
           StorageDead(_5);
           StorageDead(_4);
-          StorageDead(_6);
           return;
       }
 

diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-unwind.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-unwind.diff
@@ -103,10 +103,12 @@
           StorageDead(_9);
 -         StorageDead(_8);
 +         nop;
+          StorageDead(_6);
           goto -> bb8;
       }
 
       bb6: {
+          StorageDead(_6);
           StorageLive(_16);
           _16 = _1;
           StorageLive(_17);
@@ -130,7 +132,6 @@
       bb8: {
           StorageDead(_5);
           StorageDead(_4);
-          StorageDead(_6);
           return;
       }
 

diff --git a/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff b/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff
@@ -127,17 +127,19 @@
           StorageDead(_21);
           StorageDead(_20);
           StorageDead(_19);
+-         StorageDead(_12);
+-         StorageDead(_11);
           goto -> bb8;
       }
 
       bb7: {
+-         StorageDead(_12);
+-         StorageDead(_11);
 -         _10 = const ();
           goto -> bb8;
       }
 
       bb8: {
--         StorageDead(_12);
--         StorageDead(_11);
 -         StorageDead(_10);
           StorageLive(_22);
           StorageLive(_23);

diff --git a/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff b/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff
@@ -23,19 +23,19 @@
           StorageDead(_3);
           StorageDead(_2);
           _5 = discriminant((_1.0: std::option::Option<u8>));
-          switchInt(move _5) -> [1: bb1, 0: bb3, otherwise: bb5];
+          switchInt(move _5) -> [1: bb1, 0: bb3, otherwise: bb7];
       }
 
       bb1: {
           _4 = discriminant((_1.1: std::option::Option<T>));
-          switchInt(move _4) -> [0: bb2, 1: bb3, otherwise: bb5];
+          switchInt(move _4) -> [0: bb2, 1: bb3, otherwise: bb7];
       }
 
       bb2: {
           StorageLive(_6);
           _6 = (((_1.0: std::option::Option<u8>) as Some).0: u8);
           StorageDead(_6);
-          goto -> bb3;
+          drop(_1) -> [return: bb5, unwind unreachable];
       }
 
       bb3: {
@@ -44,10 +44,19 @@
 
       bb4: {
           StorageDead(_1);
-          return;
+          goto -> bb6;
       }
 
       bb5: {
+          StorageDead(_1);
+          goto -> bb6;
+      }
+
+      bb6: {
+          return;
+      }
+
+      bb7: {
           unreachable;
       }
   }