Summary:
Invoking `rev` does not add a trailing newline when none is present in
the input (at least on my Debian). Nearby examples use `echo` rather
than `rev`, which probably explains the source of the discrepancy.

Also, a `mut` qualifier is unused.

Test Plan:
Copy the code block into <https://play.rust-lang.org> with a `fn main`
wrapper, and run it. Note that it compiles and runs cleanly; prior to
this commit, it would emit an `unused_mut` warning and then panic.

wchargin-branch: stdio-piped-docs

…ngs_named_same_as_variants`.

…ns`.

…tern<'_>`.

Pacify `tidy`. It's also more correct in this context.

Fixes rust-lang#64412

Also tweak walkers on `Pat`.

It was never used

…errors

also removed some duplicated logic from TypeRelation methods.

…crichton

panic=abort support in libtest

Add experimental support for tests compiled with panic=abort. Enabled with `-Z panic_abort_tests`.

r? @alexcrichton
cc @cramertj

… r=Dylan-DPC

Fix `Stdio::piped` example code and lint

Summary:
Invoking `rev` does not add a trailing newline when none is present in
the input (at least on my Debian). Nearby examples use `echo` rather
than `rev`, which probably explains the source of the discrepancy.

Also, a `mut` qualifier is unused.

Test Plan:
Copy the code block into <https://play.rust-lang.org> with a `fn main`
wrapper, and run it. Note that it compiles and runs cleanly; prior to
this commit, it would emit an `unused_mut` warning and then panic.

wchargin-branch: stdio-piped-docs

or-patterns: Push `PatKind/PatternKind::Or` at top level to HIR & HAIR

Following up on work in rust-lang#64111, rust-lang#63693, and rust-lang#61708, in this PR:

- We change `hair::Arm.patterns: Vec<Pattern<'_>>` into `hir::Arm.pattern: Pattern<'_>`.

   - `fn hair::Arm::top_pats_hack` is introduced as a temporary crutch in MIR building to avoid more changes.

- We change `hir::Arm.pats: HirVec<P<Pat>>` into `hir::Arm.pat: P<Pat>`.

   - The hacks in `rustc::hir::lowering` are removed since the representation hack is no longer necessary.

   - In some places, `fn hir::Arm::top_pats_hack` is introduced to leave some things as future work.

   - Misc changes: HIR pretty printing is adjusted to behave uniformly wrt. top/inner levels, rvalue promotion is adjusted, regionck, and dead_code is also.

   - Type checking is adjusted to uniformly handle or-patterns at top/inner levels.
      To make things compile, `p_0 | ... | p_n` is redefined as a "reference pattern" in [`fn is_non_ref_pat`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_typeck/check/struct.FnCtxt.html#method.is_non_ref_pat) for now. This is done so that reference types are not eagerly stripped from the `expected: Ty<'tcx>`.

    - Liveness is adjusted wrt. the `unused_variables` and `unused_assignments` lints to handle top/inner levels uniformly and the handling of `fn` parameters, `let` locals, and `match` arms are unified in this respect. This is not tested for now as exhaustiveness checks are reachable and will ICE.

    - In `check_match`, checking `@` and by-move bindings is adjusted. However, exhaustiveness checking is not adjusted the moment and is handled by @dlrobertson in rust-lang#63688.

    - AST borrowck (`construct.rs`) is not adjusted as AST borrowck will be removed soon.

r? @matthewjasper
cc @dlrobertson @varkor @oli-obk

…e-tests, r=nikomatsakis

Bugfix/rfc 2451 rerebalance tests

r? @nikomatsakis

Fixes rust-lang#64412
Depends/Contains on rust-lang#64414

cc rust-lang#55437 and rust-lang#63599

… r=petrochenkov

Cleanup syntax::ext::build

I suspect most of this code could be inlined but I only removed the bits where the inlining didn't really hurt readability (i.e., method call -> function call) or the completely unused code.

…tril

Propagate `types.err` in locals further to avoid spurious knock-down errors

Fix rust-lang#33575, fix rust-lang#44504.

…c, r=petrochenkov

Parse assoc type bounds in generic params and provide custom diagnostic

Fix rust-lang#26271.

remove outdated comment

Infer consts more consistently

Moved some duplicated logic in `TypeRelation` methods into `super_combined_consts`. Before some `TypeRelation`s like `Lub` wasn't using `replace_if_possible`, meaning some inference types were staying around longer than they should be.

Fixes rust-lang#64519

r? @varkor