trait_sel: stash {Meta,Pointee}Sized errors

`Sized` errors are currently stashed to improve diagnostics and this
must happen with `{Meta,Pointee}Sized` too to maintain diagnostic
output.

Author: davidtwco

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

@@ -199,7 +199,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 // avoid inundating the user with unnecessary errors, but we now
                 // check upstream for type errors and don't add the obligations to
                 // begin with in those cases.
-                if self.tcx.is_lang_item(trait_pred.def_id(), LangItem::Sized) {
+                if matches!(
+                    self.tcx.as_lang_item(trait_pred.def_id()),
+                    Some(LangItem::Sized | LangItem::MetaSized)
+                ) {
                     match self.tainted_by_errors() {
                         None => {
                             let err = self.emit_inference_failure_err(