Rollup merge of #137601 - davidtwco:deduplicate-type-has-metadata, r=fmease,bjorn3

ssa/mono: deduplicate `type_has_metadata`

The implementation of the `type_has_metadata` function is duplicated in `rustc_codegen_ssa` and `rustc_monomorphize`, so move this to `rustc_middle`.

compiler/rustc_middle/src/ty/util.rs

@@ -208,6 +208,20 @@ impl<'tcx> TyCtxt<'tcx> {
         tcx.struct_tail_raw(ty, |ty| tcx.normalize_erasing_regions(typing_env, ty), || {})
     }
 
+    /// Returns true if a type has metadata.
+    pub fn type_has_metadata(self, ty: Ty<'tcx>, typing_env: ty::TypingEnv<'tcx>) -> bool {
+        if ty.is_sized(self, typing_env) {
+            return false;
+        }
+
+        let tail = self.struct_tail_for_codegen(ty, typing_env);
+        match tail.kind() {
+            ty::Foreign(..) => false,
+            ty::Str | ty::Slice(..) | ty::Dynamic(..) => true,
+            _ => bug!("unexpected unsized tail: {:?}", tail),
+        }
+    }
+
     /// Returns the deeply last field of nested structures, or the same type if
     /// not a structure at all. Corresponds to the only possible unsized field,
     /// and its type can be used to determine unsizing strategy.