Auto merge of #115138 - cjgillot:dse-move-packed, r=compiler-errors

Do not convert copies of packed projections to moves.

This code path was introduced in https://github.com/rust-lang/rust/pull/113758

After seeing https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/Packed.20fields.20and.20in-place.20function.20argument.2Freturn.20passing, this may be UB, so should be disallowed.

This should not appear in normally-built MIR, which introduces temporary copies for packed projections.

2 files changed, 2 insertions, 2 deletions

diff --git a/compiler/rustc_const_eval/src/util/alignment.rs b/compiler/rustc_const_eval/src/util/alignment.rs
index 4f39dad205a..c1f0ff260d2 100644
--- a/compiler/rustc_const_eval/src/util/alignment.rs
+++ b/compiler/rustc_const_eval/src/util/alignment.rs
@@ -40,7 +40,7 @@ where
     }
 }
 
-fn is_within_packed<'tcx, L>(
+pub fn is_within_packed<'tcx, L>(
     tcx: TyCtxt<'tcx>,
     local_decls: &L,
     place: Place<'tcx>,
diff --git a/compiler/rustc_const_eval/src/util/mod.rs b/compiler/rustc_const_eval/src/util/mod.rs
index 289e3422595..0aef7fa469e 100644
--- a/compiler/rustc_const_eval/src/util/mod.rs
+++ b/compiler/rustc_const_eval/src/util/mod.rs
@@ -5,7 +5,7 @@ mod check_validity_requirement;
 mod compare_types;
 mod type_name;
 
-pub use self::alignment::is_disaligned;
+pub use self::alignment::{is_disaligned, is_within_packed};
 pub use self::check_validity_requirement::check_validity_requirement;
 pub use self::compare_types::{is_equal_up_to_subtyping, is_subtype};
 pub use self::type_name::type_name;