Compiler hangs on type-param-error-filled project

[som-snytt]

Reproduction steps

Scala version: 2.13.10

See "Old School" or maybe the sticker says "Old Sqool" https://github.com/noresttherein/oldsql/ at linked ticket.

The CME can be diagnosed under the other ticket, but with that PR and at a certain commit, compiler fails to make progress.

Problem

Noticed at #12726