Auto merge of #97860 - Dylan-DPC:rollup-t3vxos8, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #97595 (Remove unwrap from get_vtable)
 - #97597 (Preserve unused pointer to address casts)
 - #97819 (Recover `import` instead of `use` in item)
 - #97823 (Recover missing comma after match arm)
 - #97851 (Use repr(C) when depending on struct layout in ptr tests)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_middle/src/mir/mod.rs

@@ -2605,9 +2605,34 @@ pub enum Rvalue<'tcx> {
 static_assert_size!(Rvalue<'_>, 40);
 
 impl<'tcx> Rvalue<'tcx> {
+    /// Returns true if rvalue can be safely removed when the result is unused.
     #[inline]
-    pub fn is_pointer_int_cast(&self) -> bool {
-        matches!(self, Rvalue::Cast(CastKind::PointerExposeAddress, _, _))
+    pub fn is_safe_to_remove(&self) -> bool {
+        match self {
+            // Pointer to int casts may be side-effects due to exposing the provenance.
+            // While the model is undecided, we should be conservative. See
+            // <https://www.ralfj.de/blog/2022/04/11/provenance-exposed.html>
+            Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => false,
+
+            Rvalue::Use(_)
+            | Rvalue::Repeat(_, _)
+            | Rvalue::Ref(_, _, _)
+            | Rvalue::ThreadLocalRef(_)
+            | Rvalue::AddressOf(_, _)
+            | Rvalue::Len(_)
+            | Rvalue::Cast(
+                CastKind::Misc | CastKind::Pointer(_) | CastKind::PointerFromExposedAddress,
+                _,
+                _,
+            )
+            | Rvalue::BinaryOp(_, _)
+            | Rvalue::CheckedBinaryOp(_, _)
+            | Rvalue::NullaryOp(_, _)
+            | Rvalue::UnaryOp(_, _)
+            | Rvalue::Discriminant(_)
+            | Rvalue::Aggregate(_, _)
+            | Rvalue::ShallowInitBox(_, _) => true,
+        }
     }
 }