resolve: Avoid mutating vis for distinct glob imports

[reddevilmidzy]

close: #151124

r? @petrochenkov

[reddevilmidzy]

When building Rustc locally, ICE reproduction was possible for this code without debug-assert

[petrochenkov]

This is not a correct change.
Imports are always different here (due to the remove_same_import logic above), so we never update the visibility, but we must indeed update the visibility.

This is a language problem really, this should be an ambiguity error, but we cannot report it without breakage.
And this language problem turns into annoyances in the compiler as well (like #151124).
(#149596 tries to start addressing it in some cases.)

[petrochenkov]

In the meantime it's better to relax the assert logic in compiler\rustc_middle\src\middle\privacy.rs (preferably only for globs).

[petrochenkov]

Later this week I'll try to extend the ambiguous_import_visibilities (from #149596) lint to glob-vs-glob ambiguities, this issue may also get fixed in the process.

[reddevilmidzy]

Ah, I understand. Thank you for the explanation.
As you said, I modified rustc_middle/src/middle/privacy.rs to avoid asserts.

I'll check back later to see how things are progressing.

[reddevilmidzy]

@rustbot ready