[WIP] Generic Associated Types Name Resolution

[sunjay]

This PR builds off of the to-be-merged PR for parsing generic associated types. In fact, the only new commit is the latest one which makes changes to src/librustc_resolve/lib.rs. You should look only at that file when reviewing this PR. Once the other PR is merged and this PR is rebased, the remaining files will disappear.

This PR is a work in progress and only meant to give me a way to show @nikomatsakis my progress and ask questions. I am still waiting for the build to finish locally on my computer and then I will update this PR as I find and fix errors.

Tracking Issue: #44265

r? @nikomatsakis

Notes & Questions for Reviewers

• Something to check: Am I using the right RibKind variants? I don't actually fully understand the differences from the docs in the code so it's quite possible that I didn't choose the right one.

• From the instructions by @nikomatsakis on the Tracking Issue:

  Now that generics are in place on every trait/impl item, I think we probably want to remove the handling for type and extract the method handling so that it occurs at a higher level. For the items (e.g., const) where there are no generics, then the newly introduced rib ought to be empty and hence harmless (I hope).

  I had to modify this a bit because I chose different RibKinds for Methods and Types. If it turns out the RibKind should be the same in all cases, I can lift out that call to with_type_parameter_rib and add the HasTypeParameters rib only once.

• By the end of this, the run-pass tests should actually pass! 🎉

• It's possible that I still need to add more tests before this should be merged

[sunjay]

Is ItemRibKind the right RibKind?

[sunjay]

Is ItemRibKind the right RibKind? Is this the right way to visit these types? I copied what was done for methods a few lines above this.

[bors]

☔ The latest upstream changes (presumably #45771) made this pull request unmergeable. Please resolve the merge conflicts.

[sunjay]

This has been completed and merged into the other PR I had open for parsing (#45904).