New const traits syntax

[oli-obk]

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of ~const outside of libcore have been replaced by [const]. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler.

Caveat discovered during impl: there is no legacy bare trait object recovery for [const] Trait as that snippet in type position goes down the slice /array parsing code and will error

r? @fee1-dead

cc @nikomatsakis @traviscross @compiler-errors

[rustbot]

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[bors]

☔ The latest upstream changes (presumably #140695) made this pull request unmergeable. Please resolve the merge conflicts.

[compiler-errors]

Have we actually settled on a syntax here? Sorry for punting it back over, but would like to get an update here if it's actually ready to review :> ping me when it's ready, sorry for the delays!

@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[traviscross]

Have we actually settled on a syntax here?

No. Discussion is ongoing.

[rustbot]

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

This PR modifies run-make tests.

cc @jieyouxu

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

Some changes occurred to constck

cc @fee1-dead

HIR ty lowering was modified

cc @fmease