Rollup merge of #123491 - gurry:123154-ice-unsized-struct-eval, r=oli-obk

Fix ICE in `eval_body_using_ecx`

Ensures `TypeckResults` is tainted by failing candidate assembly for types with error

Fixes #123154

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -984,7 +984,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             // Already reported in the query.
             SelectionError::NotConstEvaluatable(NotConstEvaluatable::Error(guar)) |
             // Already reported.
-            Overflow(OverflowError::Error(guar)) => return guar,
+            Overflow(OverflowError::Error(guar)) => {
+                self.set_tainted_by_errors(guar);
+                return guar
+            },
 
             Overflow(_) => {
                 bug!("overflow should be handled before the `report_selection_error` path");

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -87,6 +87,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             } else if lang_items.sized_trait() == Some(def_id) {
                 // Sized is never implementable by end-users, it is
                 // always automatically computed.
+
+                // FIXME: Consider moving this check to the top level as it
+                // may also be useful for predicates other than `Sized`
+                // Error type cannot possibly implement `Sized` (fixes #123154)
+                if let Err(e) = obligation.predicate.skip_binder().self_ty().error_reported() {
+                    return Err(SelectionError::Overflow(e.into()));
+                }
+
                 let sized_conditions = self.sized_conditions(obligation);
                 self.assemble_builtin_bound_candidates(sized_conditions, &mut candidates);
             } else if lang_items.unsize_trait() == Some(def_id) {

compiler/rustc_ty_utils/src/ty.rs

@@ -91,8 +91,8 @@ fn adt_sized_constraint<'tcx>(
     let tail_ty = tcx.type_of(tail_def.did).instantiate_identity();
 
     let constraint_ty = sized_constraint_for_ty(tcx, tail_ty)?;
-    if constraint_ty.references_error() {
-        return None;
+    if let Err(guar) = constraint_ty.error_reported() {
+        return Some(ty::EarlyBinder::bind(Ty::new_error(tcx, guar)));
     }
 
     // perf hack: if there is a `constraint_ty: Sized` bound, then we know