5 files changed, 24 insertions, 15 deletions
diff --git a/compiler/rustc_mir_transform/src/add_retag.rs b/compiler/rustc_mir_transform/src/add_retag.rs
index 3c29d4624b7..fc08c1df870 100644
--- a/compiler/rustc_mir_transform/src/add_retag.rs
+++ b/compiler/rustc_mir_transform/src/add_retag.rs
@@ -4,7 +4,6 @@
 //! of MIR building, and only after this pass we think of the program has having the
 //! normal MIR semantics.
 
-use rustc_hir::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 
@@ -28,7 +27,6 @@ fn may_contain_reference<'tcx>(ty: Ty<'tcx>, depth: u32, tcx: TyCtxt<'tcx>) -> b
         // References and Boxes (`noalias` sources)
         ty::Ref(..) => true,
         ty::Adt(..) if ty.is_box() => true,
-        ty::Adt(adt, _) if tcx.is_lang_item(adt.did(), LangItem::PtrUnique) => true,
         // Compound types: recurse
         ty::Array(ty, _) | ty::Slice(ty) => {
             // This does not branch so we keep the depth the same.
diff --git a/compiler/rustc_mir_transform/src/elaborate_drops.rs b/compiler/rustc_mir_transform/src/elaborate_drops.rs
index b4fa2be1d00..58dff4514a0 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drops.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drops.rs
@@ -253,8 +253,8 @@ struct ElaborateDropsCtxt<'a, 'tcx> {
 }
 
 impl fmt::Debug for ElaborateDropsCtxt<'_, '_> {
-    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        Ok(())
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ElaborateDropsCtxt").finish_non_exhaustive()
     }
 }
 
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index cdbc74cdfa8..6c65b072bec 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -434,8 +434,8 @@ pub(super) struct DropShimElaborator<'a, 'tcx> {
 }
 
 impl fmt::Debug for DropShimElaborator<'_, '_> {
-    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        Ok(())
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        f.debug_struct("DropShimElaborator").finish_non_exhaustive()
     }
 }
 
diff --git a/compiler/rustc_mir_transform/src/unreachable_prop.rs b/compiler/rustc_mir_transform/src/unreachable_prop.rs
index 13fb5b3e56f..c417a9272f2 100644
--- a/compiler/rustc_mir_transform/src/unreachable_prop.rs
+++ b/compiler/rustc_mir_transform/src/unreachable_prop.rs
@@ -75,7 +75,7 @@ fn remove_successors_from_switch<'tcx>(
     let is_unreachable = |bb| unreachable_blocks.contains(&bb);
 
     // If there are multiple targets, we want to keep information about reachability for codegen.
-    // For example (see tests/codegen/match-optimizes-away.rs)
+    // For example (see tests/codegen-llvm/match-optimizes-away.rs)
     //
     // pub enum Two { A, B }
     // pub fn identity(x: Two) -> Two {
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index cbb9bbfd12f..5860072d541 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -119,14 +119,16 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
     #[track_caller]
     fn fail(&self, location: Location, msg: impl AsRef<str>) {
         // We might see broken MIR when other errors have already occurred.
-        assert!(
-            self.tcx.dcx().has_errors().is_some(),
-            "broken MIR in {:?} ({}) at {:?}:\n{}",
-            self.body.source.instance,
-            self.when,
-            location,
-            msg.as_ref(),
-        );
+        if self.tcx.dcx().has_errors().is_none() {
+            span_bug!(
+                self.body.source_info(location).span,
+                "broken MIR in {:?} ({}) at {:?}:\n{}",
+                self.body.source.instance,
+                self.when,
+                location,
+                msg.as_ref(),
+            );
+        }
     }
 
     fn check_edge(&mut self, location: Location, bb: BasicBlock, edge_kind: EdgeKind) {
@@ -719,6 +721,15 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             );
                         }
 
+                        if adt_def.repr().simd() {
+                            self.fail(
+                                location,
+                                format!(
+                                    "Projecting into SIMD type {adt_def:?} is banned by MCP#838"
+                                ),
+                            );
+                        }
+
                         let var = parent_ty.variant_index.unwrap_or(FIRST_VARIANT);
                         let Some(field) = adt_def.variant(var).fields.get(f) else {
                             fail_out_of_bounds(self, location);