From abab9efbdb82b76f418115462311f8852600c9a2 Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Wed, 3 Apr 2019 21:13:51 +0100
Subject: [PATCH] Schedule storage-dead of temporaries sooner

This ensures that we will correctly generate a storage-dead if the
initializing expression diverges.
---
 src/librustc_mir/build/expr/as_temp.rs        | 40 +++++++++++++------
 src/test/mir-opt/issue-49232.rs               |  1 -
 src/test/mir-opt/match_false_edges.rs         |  6 +--
 .../mir-opt/storage_live_dead_in_statics.rs   |  2 +-
 4 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/src/librustc_mir/build/expr/as_temp.rs b/src/librustc_mir/build/expr/as_temp.rs
index c60e19701006..ac70bf30e457 100644
--- a/src/librustc_mir/build/expr/as_temp.rs
+++ b/src/librustc_mir/build/expr/as_temp.rs
@@ -1,6 +1,7 @@
 //! See docs in build/expr/mod.rs
 
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
+use crate::build::scope::{CachedBlock, DropKind};
 use crate::hair::*;
 use rustc::middle::region;
 use rustc::mir::*;
@@ -63,6 +64,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             }
             this.local_decls.push(local_decl)
         };
+        let temp_place = &Place::Base(PlaceBase::Local(temp));
+
         if !expr_ty.is_never() {
             this.cfg.push(
                 block,
@@ -71,25 +74,38 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     kind: StatementKind::StorageLive(temp),
                 },
             );
+
+            // In constants, temp_lifetime is None for temporaries that live for the
+            // 'static lifetime. Thus we do not drop these temporaries and simply leak them.
+            // This is equivalent to what `let x = &foo();` does in functions. The temporary
+            // is lifted to their surrounding scope. In a function that means the temporary lives
+            // until just before the function returns. In constants that means it outlives the
+            // constant's initialization value computation. Anything outliving a constant
+            // must have the `'static` lifetime and live forever.
+            // Anything with a shorter lifetime (e.g the `&foo()` in `bar(&foo())` or anything
+            // within a block will keep the regular drops just like runtime code.
+            if let Some(temp_lifetime) = temp_lifetime {
+                this.schedule_drop(
+                    expr_span,
+                    temp_lifetime,
+                    temp_place,
+                    expr_ty,
+                    DropKind::Storage,
+                );
+            }
         }
 
-        unpack!(block = this.into(&Place::Base(PlaceBase::Local(temp)), block, expr));
+        unpack!(block = this.into(temp_place, block, expr));
 
-        // In constants, temp_lifetime is None for temporaries that live for the
-        // 'static lifetime. Thus we do not drop these temporaries and simply leak them.
-        // This is equivalent to what `let x = &foo();` does in functions. The temporary
-        // is lifted to their surrounding scope. In a function that means the temporary lives
-        // until just before the function returns. In constants that means it outlives the
-        // constant's initialization value computation. Anything outliving a constant
-        // must have the `'static` lifetime and live forever.
-        // Anything with a shorter lifetime (e.g the `&foo()` in `bar(&foo())` or anything
-        // within a block will keep the regular drops just like runtime code.
         if let Some(temp_lifetime) = temp_lifetime {
-            this.schedule_drop_storage_and_value(
+            this.schedule_drop(
                 expr_span,
                 temp_lifetime,
-                &Place::Base(PlaceBase::Local(temp)),
+                temp_place,
                 expr_ty,
+                DropKind::Value {
+                    cached_block: CachedBlock::default(),
+                },
             );
         }
 
diff --git a/src/test/mir-opt/issue-49232.rs b/src/test/mir-opt/issue-49232.rs
index 3910183dee78..bf22f00b5055 100644
--- a/src/test/mir-opt/issue-49232.rs
+++ b/src/test/mir-opt/issue-49232.rs
@@ -86,7 +86,6 @@ fn main() {
 //         unreachable;
 //     }
 //     bb17: {
-//         StorageDead(_4);
 //         goto -> bb18;
 //     }
 //     bb18: {
diff --git a/src/test/mir-opt/match_false_edges.rs b/src/test/mir-opt/match_false_edges.rs
index 0850c552536c..6979924c8cd9 100644
--- a/src/test/mir-opt/match_false_edges.rs
+++ b/src/test/mir-opt/match_false_edges.rs
@@ -109,8 +109,8 @@ fn main() {
 //      goto -> bb13;
 //  }
 //  bb13: {
-//      StorageDead(_1);
 //      StorageDead(_2);
+//      StorageDead(_1);
 //      _0 = ();
 //      return;
 //  }
@@ -186,8 +186,8 @@ fn main() {
 //      goto -> bb13;
 //  }
 //  bb13: {
-//      StorageDead(_1);
 //      StorageDead(_2);
+//      StorageDead(_1);
 //      _0 = ();
 //      return;
 //  }
@@ -289,8 +289,8 @@ fn main() {
 //      goto -> bb17;
 //  }
 //  bb17: {
-//      StorageDead(_1);
 //      StorageDead(_2);
+//      StorageDead(_1);
 //      _0 = ();
 //      return;
 //  }
diff --git a/src/test/mir-opt/storage_live_dead_in_statics.rs b/src/test/mir-opt/storage_live_dead_in_statics.rs
index 10f00cf8b0c3..2ed34ecfad2c 100644
--- a/src/test/mir-opt/storage_live_dead_in_statics.rs
+++ b/src/test/mir-opt/storage_live_dead_in_statics.rs
@@ -182,8 +182,8 @@ fn main() {
 //        _2 = Foo { tup: const "hi", data: move _3 };
 //        _1 = &_2;
 //        _0 = &(*_1);
-//        StorageDead(_1);
 //        StorageDead(_5);
+//        StorageDead(_1);
 //        return;
 //    }
 //}