Cleanup retains annotations in all inferred type trees

[Linyxus]

fixes #20272

[mbovel]

For information, both the first test case passes in #19957, which I hope to get merged soonish.

[Linyxus]

For information, both test cases pass in #19957, which I hope to get merged soonish.

Could #19957 supersede this one?

[mbovel]

Could #19957 supersede this one?

I was hopping that correctly mapping annotations from the start could help, but I don't know if it could completely avoid the need for cleanupRetainsAnnot.

[mbovel]

I was wondering: what is the status of this PR? Did you not need it in the end?

I was also wondering: have you considered cleaning up these annotations earlier in widenInferred or such instead of doing it in PostTyper?

[Linyxus]

I cannot really remember why we did not need it in the end to capture-check the stdlib. I could check the status.

Regarding widenInferred, I was not aware of this method before, and it might be worth a try!