Rollup merge of #121470 - clubby789:anon-struct-in-enum, r=fmease

Don't ICE on anonymous struct in enum variant

Fixes #121446

Computing `adt_def` for the anon struct calls `adt_def` on the parent to find its repr. If the parent is a non-item (e.g. an enum variant) we should have already emitted at least one error, so we just use the repr of the anonymous struct to avoid an ICE.

cc ``@frank-king``

compiler/rustc_hir_analysis/src/collect.rs

@@ -1025,7 +1025,15 @@ fn adt_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AdtDef<'_> {
 
     let is_anonymous = item.ident.name == kw::Empty;
     let repr = if is_anonymous {
-        tcx.adt_def(tcx.local_parent(def_id)).repr()
+        let parent = tcx.local_parent(def_id);
+        if let Node::Item(item) = tcx.hir_node_by_def_id(parent)
+            && item.is_struct_or_union()
+        {
+            tcx.adt_def(parent).repr()
+        } else {
+            tcx.dcx().span_delayed_bug(item.span, "anonymous field inside non struct/union");
+            ty::ReprOptions::default()
+        }
     } else {
         tcx.repr_options_of_def(def_id)
     };