Auto merge of #38552 - eddyb:bad-blocks, r=arielb1

Don't leak the compiler's internal representation of scopes in error messages.

Fixes #37884 (actually fixes #27942, which was made worse by #37412) by handling more node types.
Ideally we'd turn the unknown node type situations into ICEs and fix them as they show up in errors.
But we might want to backport this patch so I was less aggressive.