ConstProp: Remove const when rvalue check fails.

(cherry picked from commit 9121a41)

Author: aDotInTheVoid

compiler/rustc_mir_transform/src/const_prop.rs

@@ -440,6 +440,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
         // FIXME we need to revisit this for #67176
         if rvalue.has_param() {
+            trace!("skipping, has param");
             return None;
         }
         if !rvalue
@@ -708,7 +709,11 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
     fn visit_assign(&mut self, place: &Place<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
         self.super_assign(place, rvalue, location);
 
-        let Some(()) = self.check_rvalue(rvalue) else { return };
+        let Some(()) = self.check_rvalue(rvalue) else {
+            trace!("rvalue check failed, removing const");
+            Self::remove_const(&mut self.ecx, place.local);
+            return;
+        };
 
         match self.ecx.machine.can_const_prop[place.local] {
             // Do nothing if the place is indirect.

tests/mir-opt/const_prop/issue_118328.size_of.ConstProp.diff

@@ -12,8 +12,7 @@
           StorageLive(_1);
           _1 = const 0_usize;
           _1 = const _;
--         _0 = _1;
-+         _0 = const 0_usize;
+          _0 = _1;
           StorageDead(_1);
           return;
       }