Fix test style in unused parentheses lint test
I think this fixes#63237
I'm not sure if I had to add text after the `//~ ERROR` comments.
This is my first pull request, so I'm open to feedback.
This issues already received one pull request [here](https://github.com/rust-lang/rust/pull/63257) but it was marked as closed for inactivity.
r? @nikomatsakis
Add more coherence tests
I've wrote the missing test cases listed in [this google doc](https://docs.google.com/spreadsheets/d/1WlroTEXE6qxxGvEOhICkUpqguYZP9YOZEvnmEtSNtM0/edit#gid=0)
> The other thing that might be useful is to rename the existing tests so they all fit the new naming scheme we were using.
I'm not entirely sure how to do this. If everything from the google sheet is covered could I just remove the remaining tests in `src/test/ui/coherence` or is there something in there that should remain?
cc #63599
r? @nikomatsakis
Mention keyword closing policy
closes#59233 / https://github.com/rust-lang/rust/issues/59233#issuecomment-478362693
rewording suggestions welcome
> Also in the referenced issue, the commit number of the new commit
> that could close that issue is not really informative. The PR number itself appeared in the issue
> is more informative and concise.
@lzutao what do you mean with that? Is this fixed by the new "May be fixed by #XXXXX"?
Refactor libtest
## Short overview
`libtest` got refactored and splitted into smaller modules
## Description
`libtest` module is already pretty big and hard to understand. Everything is mixed up: CLI, console output, test execution, etc.
This PR splits `libtest` into smaller logically-consistent modules, makes big functions smaller and more readable, and adds more comments, so `libtest` will be easier to understand and maintain.
Although there are a lot of changes, all the refactoring is "soft", meaning that no public interfaces were affected and nothing should be broken.
Thus this PR (at least should be) completely backward-compatible.
r? @wesleywiser
cc @Centril
Remove `src/llvm-emscripten` submodule
With #65251 landed there's no need to build two LLVM backends and ship
them with rustc, every target we have now uses the same LLVM backend!
This removes the `src/llvm-emscripten` submodule and additionally
removes all support from rustbuild for building the emscripten LLVM
backend. Multiple codegen backend support is left in place for now, and
this is intended to be an easy 10-15 minute win on CI times by avoiding
having to build LLVM twice.
