Currently mirrors are stored in the rust-lang-ci2 S3 bucket along with
CI toolchains. This is problematic for multiple reasons:

- CI IAM credentials are allowed to both edit and delete those files.
  A malicious user gaining access to those credentials would be able to
  change our mirrored dependencies, possibly backdooring the compiler.

- Contents of the rust-lang-ci2 bucket are disposable except for the
  mirrors' content. When we implement backups for S3 buckets we'd have
  to replicate just that part of the bucket, complicating the backup
  logic and increasing the chance of mistakes. A standalone bucket will
  be way easier to backup.

This commit switches our CI to use the new rust-lang-ci-mirrors bucket.

Closes rust-lang#62632

This fixes handling default configuration for the `crate_blacklist`
RLS configuration.

Technically this isn't needed, as the VS Code extension can be
configured to accept a predefined blacklist that's equal to the default
one but it's best that it also lands so that we don't need to work
around that.

cc rust-lang#63472

This commit prohibits return position `impl Trait` types that "inherit
lifetimes" from the parent scope. The intent is to forbid cases that are
challenging until they can be addressed properly.

This is needed to permit us building core_arch which is a submodule dep
(so we can't snap it to the new beta compiler).

…ackmdavis

Deduplicate error messages in `librsctc_mir`

Deduplicated the error messages in `librustc_mir`. rust-lang#62022

…imes, r=nikomatsakis

typeck: Prohibit RPIT types that inherit lifetimes

Part of rust-lang#61949.

This PR prohibits return position `impl Trait` types that "inherit
lifetimes" from the parent scope. The intent is to forbid cases that are
challenging until they can be addressed properly.

cc @nikomatsakis

…s, r=nikomatsakis

`async fn` lifetime elision tests

Add `async fn` version of the tests in rust-lang#61207 per the first checkbox in rust-lang#62121 (comment).
Works towards resolving blockers in rust-lang#63209.

r? @nikomatsakis
cc @cramertj

Implement Clone, Display for ascii::EscapeDefault

This will mimic the same behaviour as the `char` version; `Display`ing the iterator will give its string representation without advancing it.

syntax: account for CVarArgs being in the argument list.

Fixes rust-lang#63430 by testing for `1` argument (the `CVarArgs` itself) instead of `0`.

Note that the error has basically been impossible to trigger since the change that caused rust-lang#63430, so perhaps we need an audit of untested errors.

Also, this check probably belongs in AST validation/HIR lowering, but I'd rather fix it in place for now.

r? @petrochenkov cc @dlrobertson

…xcrichton

Utilize -Zbinary-dep-depinfo in rustbuild

The last commit moves us over to using binary-dep-depinfo while the first two permit us to bootstrap from what will become future beta, to be released in the next week (it's the `cfg(bootstrap)` processing).

We no longer utilize stamp-file mtimes at all inside rustbuild, and a future PR may be able to entirely eliminate them by eagerly copying to the appropriate sysroot. The only mtime-based dependency tracking left is for documentation because we lie to Cargo about the rustdoc binary, so Cargo does not track changes to the real binary, and codegen-backends because binary-dep-depinfo does not emit that information into the depfiles.

Both of these are fixable in the longer term but this existing patch gives us the following benefits:
 * We no longer delete Cargo target directories manually within a stage. Cross-stage, changes to codegen backends will still clear out target directories. This means that incremental state persists across individual steps (e.g., rebuilding libstd does not clear out librustc incremental state). Fixes rust-lang#54712.
 * Dependency tracking across steps within a given stage is now fully precise. We will not clear out all codegen backend dependencies due to changes in librustc_driver, for example, only deleting the final librustc_codegen_llvm crate. Fixes rust-lang#54008, fixes rust-lang#50481.
 * We properly track codegen backends as a dependency (equivalent to rustc) across changes. Fixes rust-lang#53284, and fixes rust-lang#52719.
 * Cross-stage dependency tracking of crates is also much more accurate and reliable. Most likely fixes rust-lang#49979 (but no reproduction steps in that issue). Fixes rust-lang#59105.

cc rust-lang#63012

Bring back suggestion for splitting `<-` into `< -`

Closes rust-lang#62632

…lexcrichton

ci: move mirrors to their standalone bucket

Currently mirrors are stored in the rust-lang-ci2 S3 bucket along with
CI toolchains. This is problematic for multiple reasons:

- CI IAM credentials are allowed to both edit and delete those files.
  A malicious user gaining access to those credentials would be able to
  change our mirrored dependencies, possibly compromising the compiler.

- Contents of the rust-lang-ci2 bucket are disposable except for the
  mirrors' content. When we implement backups for S3 buckets we'd have
  to replicate just that part of the bucket, complicating the backup
  logic and increasing the chance of mistakes. A standalone bucket will
  be way easier to backup.

This commit switches our CI to use the new rust-lang-ci-mirrors bucket.

r? @alexcrichton

improve DiagnosticBuilder docs

Cc @estebank @oli-obk

Is there any way to do something like `span_note` but with a label attached to the span? I thought `.span_note().span_label()` would do it, but no, that does not work.

Update RLS

This fixes handling default configuration for the `crate_blacklist`
RLS configuration.

Technically this isn't needed, as the VS Code extension can be
configured to accept a predefined blacklist that's equal to the default
one but it's best that it also lands so that we don't need to work
around that.

Without this, manually passing a `null` value as the configuration
unfortunately crashes the RLS. This is the last fix related to configuration.

cc rust-lang#63472

r? @Mark-Simulacrum

Bump to 1.39

r? @Centril