Sema: disallow unsafe in-memory coercions

The error messages here aren't amazing yet, but this is an improvement
on status quo, because the current behavior allows false negative
compile errors, so effectively miscompiles.

Resolves: #15874
f154cd1fdcmlugg committed on 12/16/2024, 2:53:54 PMparentd12c0bf
5 files changedLine totals unavailable