Hide errors whose suggestions would contain error constants or types

Author: oli-obk

Diff for: compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -998,6 +998,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                         self.lower_const_arg(ct, FeedConstTy::No).into()
                                     }
                                 };
+                                if term.references_error() {
+                                    continue;
+                                }
                                 // FIXME(#97583): This isn't syntactically well-formed!
                                 where_bounds.push(format!(
                                     "        T: {trait}::{assoc_name} = {term}",

Diff for: tests/ui/associated-consts/assoc-const-eq-ambiguity.stderr

@@ -26,12 +26,6 @@ LL | trait Parent2 { const C: &'static str; }
 LL |
 LL | fn take1(_: impl Trait1<C = "?">) {}
    |                         ^^^^^^^ ambiguous associated constant `C`
-   |
-   = help: consider introducing a new type parameter `T` and adding `where` constraints:
-               where
-                   T: Trait1,
-                   T: Parent2::C = {const error},
-                   T: Parent1::C = {const error}
 
 error: aborting due to 2 previous errors