Auto merge of #74746 - wesleywiser:stable_backport_73669, r=Mark-Simulacrum1.45.1

Stable backport of #73613

This is the backport of #73613 to stable.

r? @ghost

cc @Mark-Simulacrum

In addition the tests added in the original PR passing, I've also confirmed that the test case in #74739 works correctly.

14 files changed, 207 insertions, 108 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3006e61b818..68b779347dd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -101,9 +101,6 @@ jobs:
       - name: install MSYS2
         run: src/ci/scripts/install-msys2.sh
         if: success() && !env.SKIP_JOB
-      - name: install MSYS2 packages
-        run: src/ci/scripts/install-msys2-packages.sh
-        if: success() && !env.SKIP_JOB
       - name: install MinGW
         run: src/ci/scripts/install-mingw.sh
         if: success() && !env.SKIP_JOB
@@ -210,9 +207,6 @@ jobs:
       - name: install MSYS2
         run: src/ci/scripts/install-msys2.sh
         if: success() && !env.SKIP_JOB
-      - name: install MSYS2 packages
-        run: src/ci/scripts/install-msys2-packages.sh
-        if: success() && !env.SKIP_JOB
       - name: install MinGW
         run: src/ci/scripts/install-mingw.sh
         if: success() && !env.SKIP_JOB
@@ -561,9 +555,6 @@ jobs:
       - name: install MSYS2
         run: src/ci/scripts/install-msys2.sh
         if: success() && !env.SKIP_JOB
-      - name: install MSYS2 packages
-        run: src/ci/scripts/install-msys2-packages.sh
-        if: success() && !env.SKIP_JOB
       - name: install MinGW
         run: src/ci/scripts/install-mingw.sh
         if: success() && !env.SKIP_JOB
diff --git a/RELEASES.md b/RELEASES.md
index 12b04bcce19..204741bec5a 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,10 +1,12 @@
 Version 1.45.1 (2020-07-30)
 ==========================
 
+* [Fix const propagation with references.][73613]
 * [rustfmt accepts rustfmt_skip in cfg_attr again.][73078]
 * [Avoid spurious implicit region bound.][74509]
 * [Install clippy on x.py install][74457]
 
+[73613]: https://github.com/rust-lang/rust/pull/73613
 [73078]: https://github.com/rust-lang/rust/issues/73078
 [74509]: https://github.com/rust-lang/rust/pull/74509
 [74457]: https://github.com/rust-lang/rust/pull/74457
diff --git a/src/ci/azure-pipelines/steps/run.yml b/src/ci/azure-pipelines/steps/run.yml
index 85ff3e52a84..e43116c06b6 100644
--- a/src/ci/azure-pipelines/steps/run.yml
+++ b/src/ci/azure-pipelines/steps/run.yml
@@ -82,10 +82,6 @@ steps:
   displayName: Install msys2
   condition: and(succeeded(), not(variables.SKIP_JOB))
 
-- bash: src/ci/scripts/install-msys2-packages.sh
-  displayName: Install msys2 packages
-  condition: and(succeeded(), not(variables.SKIP_JOB))
-
 - bash: src/ci/scripts/install-mingw.sh
   displayName: Install MinGW
   condition: and(succeeded(), not(variables.SKIP_JOB))
diff --git a/src/ci/github-actions/ci.yml b/src/ci/github-actions/ci.yml
index 1cf828fd64e..3404d024255 100644
--- a/src/ci/github-actions/ci.yml
+++ b/src/ci/github-actions/ci.yml
@@ -146,10 +146,6 @@ x--expand-yaml-anchors--remove:
         run: src/ci/scripts/install-msys2.sh
         <<: *step
 
-      - name: install MSYS2 packages
-        run: src/ci/scripts/install-msys2-packages.sh
-        <<: *step
-
       - name: install MinGW
         run: src/ci/scripts/install-mingw.sh
         <<: *step
diff --git a/src/ci/scripts/install-msys2-packages.sh b/src/ci/scripts/install-msys2-packages.sh
deleted file mode 100755
index ff7479c05d0..00000000000
--- a/src/ci/scripts/install-msys2-packages.sh
+++ /dev/null
@@ -1,27 +0,0 @@
-#!/bin/bash
-
-set -euo pipefail
-IFS=$'\n\t'
-
-source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
-
-if isWindows; then
-    pacman -S --noconfirm --needed base-devel ca-certificates make diffutils tar \
-        binutils
-
-    # Detect the native Python version installed on the agent. On GitHub
-    # Actions, the C:\hostedtoolcache\windows\Python directory contains a
-    # subdirectory for each installed Python version.
-    #
-    # The -V flag of the sort command sorts the input by version number.
-    native_python_version="$(ls /c/hostedtoolcache/windows/Python | sort -Vr | head -n 1)"
-
-    # Make sure we use the native python interpreter instead of some msys equivalent
-    # one way or another. The msys interpreters seem to have weird path conversions
-    # baked in which break LLVM's build system one way or another, so let's use the
-    # native version which keeps everything as native as possible.
-    python_home="/c/hostedtoolcache/windows/Python/${native_python_version}/x64"
-    cp "${python_home}/python.exe" "${python_home}/python3.exe"
-    ciCommandAddPath "C:\\hostedtoolcache\\windows\\Python\\${native_python_version}\\x64"
-    ciCommandAddPath "C:\\hostedtoolcache\\windows\\Python\\${native_python_version}\\x64\\Scripts"
-fi
diff --git a/src/ci/scripts/install-msys2.sh b/src/ci/scripts/install-msys2.sh
index 0ecc14b9468..185d3615825 100755
--- a/src/ci/scripts/install-msys2.sh
+++ b/src/ci/scripts/install-msys2.sh
@@ -1,10 +1,6 @@
 #!/bin/bash
 # Download and install MSYS2, needed primarily for the test suite (run-make) but
 # also used by the MinGW toolchain for assembling things.
-#
-# FIXME: we should probe the default azure image and see if we can use the MSYS2
-# toolchain there. (if there's even one there). For now though this gets the job
-# done.
 
 set -euo pipefail
 IFS=$'\n\t'
@@ -12,16 +8,9 @@ IFS=$'\n\t'
 source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 
 if isWindows; then
-    # Pre-followed the api/v2 URL to the CDN since the API can be a bit flakey
-    curl -sSL https://packages.chocolatey.org/msys2.20190524.0.0.20191030.nupkg > \
-        msys2.nupkg
-    curl -sSL https://packages.chocolatey.org/chocolatey-core.extension.1.3.5.1.nupkg > \
-        chocolatey-core.extension.nupkg
-    choco install -s . msys2 \
-        --params="/InstallDir:$(ciCheckoutPath)/msys2 /NoPath" -y --no-progress
-    rm msys2.nupkg chocolatey-core.extension.nupkg
-    mkdir -p "$(ciCheckoutPath)/msys2/home/${USERNAME}"
-    ciCommandAddPath "$(ciCheckoutPath)/msys2/usr/bin"
+    msys2Path="c:/msys64"
+    mkdir -p "${msys2Path}/home/${USERNAME}"
+    ciCommandAddPath "${msys2Path}/usr/bin"
 
     # Detect the native Python version installed on the agent. On GitHub
     # Actions, the C:\hostedtoolcache\windows\Python directory contains a
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 92000e64113..75032eafe30 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -580,8 +580,16 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             }
 
             // Do not try creating references (#67862)
-            Rvalue::Ref(_, _, place_ref) => {
-                trace!("skipping Ref({:?})", place_ref);
+            Rvalue::AddressOf(_, place) | Rvalue::Ref(_, _, place) => {
+                trace!("skipping AddressOf | Ref for {:?}", place);
+
+                // This may be creating mutable references or immutable references to cells.
+                // If that happens, the pointed to value could be mutated via that reference.
+                // Since we aren't tracking references, the const propagator loses track of what
+                // value the local has right now.
+                // Thus, all locals that have their reference taken
+                // must not take part in propagation.
+                Self::remove_const(&mut self.ecx, place.local);
 
                 return None;
             }
@@ -726,7 +734,8 @@ enum ConstPropMode {
     OnlyInsideOwnBlock,
     /// The `Local` can be propagated into but reads cannot be propagated.
     OnlyPropagateInto,
-    /// No propagation is allowed at all.
+    /// The `Local` cannot be part of propagation at all. Any statement
+    /// referencing it either for reading or writing will not get propagated.
     NoPropagation,
 }
 
@@ -793,7 +802,9 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
                         // end of the block anyway, and inside the block we overwrite previous
                         // states as applicable.
                         ConstPropMode::OnlyInsideOwnBlock => {}
-                        other => {
+                        ConstPropMode::NoPropagation => {}
+                        ConstPropMode::OnlyPropagateInto => {}
+                        other @ ConstPropMode::FullConstProp => {
                             trace!(
                                 "local {:?} can't be propagated because of multiple assignments",
                                 local,
@@ -880,13 +891,22 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                             }
                         }
                     }
-                    if can_const_prop == ConstPropMode::OnlyPropagateInto
-                        || can_const_prop == ConstPropMode::NoPropagation
-                    {
-                        trace!("can't propagate into {:?}", place);
-                        if place.local != RETURN_PLACE {
-                            Self::remove_const(&mut self.ecx, place.local);
+                    match can_const_prop {
+                        ConstPropMode::OnlyInsideOwnBlock => {
+                            trace!(
+                                "found local restricted to its block. \
+                                Will remove it from const-prop after block is finished. Local: {:?}",
+                                place.local
+                            );
+                            self.locals_of_current_block.insert(place.local);
+                        }
+                        ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
+                            trace!("can't propagate into {:?}", place);
+                            if place.local != RETURN_PLACE {
+                                Self::remove_const(&mut self.ecx, place.local);
+                            }
                         }
+                        ConstPropMode::FullConstProp => {}
                     }
                 } else {
                     // Const prop failed, so erase the destination, ensuring that whatever happens
@@ -906,6 +926,12 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                     );
                     Self::remove_const(&mut self.ecx, place.local);
                 }
+            } else {
+                trace!(
+                    "cannot propagate into {:?}, because the type of the local is generic.",
+                    place,
+                );
+                Self::remove_const(&mut self.ecx, place.local);
             }
         } else {
             match statement.kind {
diff --git a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
index 7071f31dbf1..7ceec94d81e 100644
--- a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
@@ -46,22 +46,8 @@
                                            // mir::Constant
                                            // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
                                            // + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
--         _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
--         _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+         _7 = const 3usize;               // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: usize
-+                                          // + val: Value(Scalar(0x00000003))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
-+         _8 = const false;                // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x00))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
+          _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
+          _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
           assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
       }
   
diff --git a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
index 15995ab0700..483a6f232ef 100644
--- a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
@@ -46,22 +46,8 @@
                                            // mir::Constant
                                            // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
                                            // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
--         _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
--         _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+         _7 = const 3usize;               // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: usize
-+                                          // + val: Value(Scalar(0x0000000000000003))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
-+         _8 = const false;                // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x00))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
+          _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
+          _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
           assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
       }
   
diff --git a/src/test/mir-opt/const_prop_miscompile.rs b/src/test/mir-opt/const_prop_miscompile.rs
new file mode 100644
index 00000000000..043b22870f4
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile.rs
@@ -0,0 +1,22 @@
+#![feature(raw_ref_op)]
+
+// EMIT_MIR rustc.foo.ConstProp.diff
+fn foo() {
+    let mut u = (1,);
+    *&mut u.0 = 5;
+    let y = { u.0 } == 5;
+}
+
+// EMIT_MIR rustc.bar.ConstProp.diff
+fn bar() {
+    let mut v = (1,);
+    unsafe {
+        *&raw mut v.0 = 5;
+    }
+    let y = { v.0 } == 5;
+}
+
+fn main() {
+    foo();
+    bar();
+}
diff --git a/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff b/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff
new file mode 100644
index 00000000000..c87f67bf9f5
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff
@@ -0,0 +1,75 @@
+- // MIR for `bar` before ConstProp
++ // MIR for `bar` after ConstProp
+  
+  fn bar() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/const_prop_miscompile.rs:11:10: 11:10
+      let mut _1: (i32,);                  // in scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+      let _2: ();                          // in scope 0 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+      let mut _3: *mut i32;                // in scope 0 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+      let mut _5: i32;                     // in scope 0 at $DIR/const_prop_miscompile.rs:16:13: 16:20
+      scope 1 {
+          debug v => _1;                   // in scope 1 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+          let _4: bool;                    // in scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          scope 2 {
+          }
+          scope 3 {
+              debug y => _4;               // in scope 3 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+-         _1 = (const 1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
++         _1 = const (1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
+                                           // ty::Const
+-                                          // + ty: i32
++                                          // + ty: (i32,)
+                                           // + val: Value(Scalar(0x00000001))
+                                           // mir::Constant
+-                                          // + span: $DIR/const_prop_miscompile.rs:12:18: 12:19
+-                                          // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
++                                          // + span: $DIR/const_prop_miscompile.rs:12:17: 12:21
++                                          // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
+          StorageLive(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+          StorageLive(_3);                 // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+          _3 = &raw mut (_1.0: i32);       // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+          (*_3) = const 5i32;              // scope 2 at $DIR/const_prop_miscompile.rs:14:9: 14:26
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:14:25: 14:26
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_3);                 // scope 2 at $DIR/const_prop_miscompile.rs:14:26: 14:27
+          _2 = const ();                   // scope 2 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:13:5: 15:6
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:15:5: 15:6
+          StorageLive(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          StorageLive(_5);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:20
+          _5 = (_1.0: i32);                // scope 1 at $DIR/const_prop_miscompile.rs:16:15: 16:18
+          _4 = Eq(move _5, const 5i32);    // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:25
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:16:24: 16:25
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_5);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:24: 16:25
+          _0 = const ();                   // scope 0 at $DIR/const_prop_miscompile.rs:11:10: 17:2
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:11:10: 17:2
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:17:1: 17:2
+          StorageDead(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:17:1: 17:2
+          return;                          // scope 0 at $DIR/const_prop_miscompile.rs:17:2: 17:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff b/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff
new file mode 100644
index 00000000000..8a6850d2fe3
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff
@@ -0,0 +1,63 @@
+- // MIR for `foo` before ConstProp
++ // MIR for `foo` after ConstProp
+  
+  fn foo() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/const_prop_miscompile.rs:4:10: 4:10
+      let mut _1: (i32,);                  // in scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+      let mut _2: &mut i32;                // in scope 0 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+      let mut _4: i32;                     // in scope 0 at $DIR/const_prop_miscompile.rs:7:13: 7:20
+      scope 1 {
+          debug u => _1;                   // in scope 1 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+          let _3: bool;                    // in scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          scope 2 {
+              debug y => _3;               // in scope 2 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+-         _1 = (const 1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
++         _1 = const (1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
+                                           // ty::Const
+-                                          // + ty: i32
++                                          // + ty: (i32,)
+                                           // + val: Value(Scalar(0x00000001))
+                                           // mir::Constant
+-                                          // + span: $DIR/const_prop_miscompile.rs:5:18: 5:19
+-                                          // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
++                                          // + span: $DIR/const_prop_miscompile.rs:5:17: 5:21
++                                          // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
+          StorageLive(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+          _2 = &mut (_1.0: i32);           // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+          (*_2) = const 5i32;              // scope 1 at $DIR/const_prop_miscompile.rs:6:5: 6:18
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:6:17: 6:18
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:6:18: 6:19
+          StorageLive(_3);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          StorageLive(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:20
+          _4 = (_1.0: i32);                // scope 1 at $DIR/const_prop_miscompile.rs:7:15: 7:18
+          _3 = Eq(move _4, const 5i32);    // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:25
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:7:24: 7:25
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:24: 7:25
+          _0 = const ();                   // scope 0 at $DIR/const_prop_miscompile.rs:4:10: 8:2
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:4:10: 8:2
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_3);                 // scope 1 at $DIR/const_prop_miscompile.rs:8:1: 8:2
+          StorageDead(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:8:1: 8:2
+          return;                          // scope 0 at $DIR/const_prop_miscompile.rs:8:2: 8:2
+      }
+  }
+  
diff --git a/src/test/ui/mir/mir_detects_invalid_ops.rs b/src/test/ui/mir/mir_detects_invalid_ops.rs
index 0940dbe6a5e..136c03cd9f1 100644
--- a/src/test/ui/mir/mir_detects_invalid_ops.rs
+++ b/src/test/ui/mir/mir_detects_invalid_ops.rs
@@ -19,6 +19,6 @@ fn mod_by_zero() {
 fn oob_error_for_slices() {
     let a: *const [_] = &[1, 2, 3];
     unsafe {
-        let _b = (*a)[3]; //~ ERROR this operation will panic at runtime [unconditional_panic]
+        let _b = (*a)[3];
     }
 }
diff --git a/src/test/ui/mir/mir_detects_invalid_ops.stderr b/src/test/ui/mir/mir_detects_invalid_ops.stderr
index 41f03789f23..0b6dbfd7c3d 100644
--- a/src/test/ui/mir/mir_detects_invalid_ops.stderr
+++ b/src/test/ui/mir/mir_detects_invalid_ops.stderr
@@ -12,11 +12,5 @@ error: this operation will panic at runtime
 LL |     let _z = 1 % y;
    |              ^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: this operation will panic at runtime
-  --> $DIR/mir_detects_invalid_ops.rs:22:18
-   |
-LL |         let _b = (*a)[3];
-   |                  ^^^^^^^ index out of bounds: the len is 3 but the index is 3
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors