Fixes #46018

(thanks again @holly-cummins for spotting this...)

I had to make a few changes to the tests, which were quite thoroughly broken. Not even compiling.

Even though we went (quite) some time without running these tests, it looks like we got lucky: tests still pass, and (critically) native compilation works fine.

I'd recommend trying to backport to (at least) 3.15 to make sure things are alright there too...