I don't have a test case for this yet, but the fix in #5225 almost certainly also needs to be applied two the two spots in MatchFunctions that call GroupIdsAndMatch with Differ::GroupIdsHelperGetTypeId, which is never the right thing to do, since it ignores the established src/dst mappings for types.

I have a fix for this, and if you prefer, I can just fold it into #5225. But the fix doesn't have any effect on test/diff/diff_files, meaning that (assuming that there is indeed a bug here - it seems clear) it doesn't have any test coverage. Rather than expand the scope of #5218, I filed this separate issue.