Auto merge of #30676 - nikomatsakis:issue-29857, r=arielb1

This is an alternative to https://github.com/rust-lang/rust/pull/29954 for fixing #29857 that seems to me to be more inline with the general strategy around `TyError`. It also includes the fix for #30589 -- in fact, just the minimal change of making `ty_is_local` tolerate `TyError` avoids the ICE, but you get a lot of duplicate error reports, so in the case where the impl's trait reference already includes `TyError`, we just ignore the impl altogether.

cc @arielb1 @sanxiyn

Fixes #29857.
Fixes #30589.