Per rust-lang/rfcs#3671.

We can replace some tricky iterator-mutation code with a much simpler version
that uses `while let` to shrink a slice.

We also check whether a subpattern would be a wildcard _before_ hoisting it,
which will be very useful when trying to get rid of `print::PatKind` later.

Rather than writing character at a time, optimise Debug implementation
for core::ascii::Char such that it writes the entire representation as
with a single write_str call.

With that, add tests for Display and Debug implementations.

core: optimise Debug impl for ascii::Char

Rather than writing character at a time, optimise Debug implementation
for core::ascii::Char such that it writes the entire representation
with a single write_str call.

With that, add tests for Display and Debug.

Issue: rust-lang#110998

Preliminary cleanup of `WitnessPat` hoisting/printing

Follow-up to rust-lang#128430.

The eventual goal is to remove `print::Pat` entirely, but in the course of working towards that I made so many small improvements that it seems wise to let those be reviewed/merged on their own first.

Best reviewed commit-by-commit, most of which should be pretty simple and straightforward.

r? ``@Nadrieril``

…imulacrum

Promote aarch64-apple-darwin to Tier 1

This promotes aarch64-apple-darwin to Tier 1 status as per rust-lang/rfcs#3671 and tracking issue rust-lang#73908. Not sure what else is necessary for this to impement the aforementioned RFC, however I figured I'd try. I did read in previous issues and PRs that the necessary infrastructure was already in place for the aarch64-apple-darwin target, and the RFC mentions the same. So this should be all thats necessary in order for the target to be promoted.

This is a recreation of my previous PR because I accidentally did an incorrect git rebase which caused unnecessary changes to various commit SHAs. So this PR is a recreation of my previous PR without said stumble. My bad.

…iler-errors

Use more slice patterns inside the compiler

Nothing super noteworthy. Just replacing the common 'fragile' pattern of "length check followed by indexing or unwrap" with slice patterns for legibility and 'robustness'.

r? ghost

…rochenkov

rm `import.used`

By the way, `import_used_map` will only be used during `build_reduced_graph` and `finalize`, so it can be split from `Resolver` in the future.

r? ``@petrochenkov``

…cuviper

make LocalWaker::will_wake consistent with Waker::will_wake

This mirrors rust-lang#119863 for `LocalWaker`. Looks like that got missed in the initial `LocalWaker` PR (rust-lang#118960).