Auto merge of #143116 - matthiaskrgr:rollup-zy9ez06, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#139858 (New const traits syntax)
 - rust-lang/rust#140809 (Reduce special casing for the panic runtime)
 - rust-lang/rust#142730 (suggest declaring modules when file found but module not defined)
 - rust-lang/rust#142806 (Normalize before computing ConstArgHasType goal in new solver)
 - rust-lang/rust#143046 (const validation: properly ignore zero-sized UnsafeCell)
 - rust-lang/rust#143092 (const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology)
 - rust-lang/rust#143096 (tag_for_variant: properly pass TypingEnv)
 - rust-lang/rust#143104 (hir_analysis: prohibit `dyn PointeeSized`)
 - rust-lang/rust#143106 (gce: don't ICE on non-local const)

Failed merges:

 - rust-lang/rust#143036 (Remove support for `dyn*` from the compiler)

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

1 files changed, 10 insertions, 5 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 099ee4e16ff..998ef3729ea 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -494,7 +494,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         }
         // Make sure this is dereferenceable and all.
         let size_and_align = try_validation!(
-            self.ecx.size_and_align_of_mplace(&place),
+            self.ecx.size_and_align_of_val(&place),
             self.path,
             Ub(InvalidMeta(msg)) => match msg {
                 InvalidMetaKind::SliceTooBig => InvalidMetaSliceTooLarge { ptr_kind },
@@ -906,7 +906,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         let (_prov, start_offset) = mplace.ptr().into_parts();
         let (size, _align) = self
             .ecx
-            .size_and_align_of_mplace(&mplace)?
+            .size_and_align_of_val(&mplace)?
             .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
         // If there is no padding at all, we can skip the rest: check for
         // a single data range covering the entire value.
@@ -1086,8 +1086,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
     ) -> InterpResult<'tcx> {
         // Special check for CTFE validation, preventing `UnsafeCell` inside unions in immutable memory.
         if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if !val.layout.is_zst() && !val.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.typing_env)
-            {
+            // Unsized unions are currently not a thing, but let's keep this code consistent with
+            // the check in `visit_value`.
+            let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
+            if !zst && !val.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.typing_env) {
                 if !self.in_mutable_memory(val) {
                     throw_validation_failure!(self.path, UnsafeCellInImmutable);
                 }
@@ -1131,7 +1133,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
 
         // Special check preventing `UnsafeCell` in the inner part of constants
         if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if !val.layout.is_zst()
+            // Exclude ZST values. We need to compute the dynamic size/align to properly
+            // handle slices and trait objects.
+            let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
+            if !zst
                 && let Some(def) = val.layout.ty.ty_adt_def()
                 && def.is_unsafe_cell()
             {