Co-Authored-By: kennytm <[email protected]>

Co-Authored-By: Ralf Jung <[email protected]>

Co-Authored-By: Ralf Jung <[email protected]>

Co-Authored-By: kennytm <[email protected]>

- Make sure we ban duplicate '..'.
- Avoid ICEs on PatKind::Rest that doesn't generate HIR nodes.

- Make sure extra `x @ ..` do not cause ICEs.

Implement RFC 2707 + Parser recovery for range patterns

Implement rust-lang/rfcs#2707.

- Add a new basic syntactic pattern form `ast::PatKind::Rest` (parsed as `..` or `DOTDOT`) and simplify `ast::PatKind::{Slice, Tuple, TupleStruct}` as a result.

- Lower `ast::PatKind::Rest` in combination with the aforementioned `PatKind` variants as well as `PatKind::Ident`. The HIR remains unchanged for now (may be advisable to make slight adjustments later).

- Refactor `parser.rs` wrt. parsing sequences and lists of things in the process.

- Add parser recovery for range patterns of form `X..`, `X..=`, `X...`, `..Y`, `..=Y`, and `...Y`.
   This should make it easy to actually support these patterns semantically later if we so desire.

cc rust-lang#62254

r? @petrochenkov

…k, r=kennytm

Actually add rustc-guide to toolstate, don't fail builds for the guide

cc @ehuss

r? @kennytm

Fix few Clippy warnings

bump crossbeam-epoch dependency

The new crossbeam-epoch release depends on a memoffset with a whole bunch of soundness holes fixed.

The old memoffset is still indirectly depended on (at least) by rustc-rayon, though -- a crate that looks rather unmaintained (no change in more than a year).

Avoid ICE when referencing desugared local binding in borrow error

To avoid leaking the names of local bindings from expressions like for loops, rust-lang#60984 explicitly ignored them, but an assertion that `LocalKind::Var` *must* have a name would trigger an ICE.

Before this change, the binding generated by desugaring the for loop would leak into the diagnostic (rust-lang#63027):
```
error[E0515]: cannot return value referencing local variable `__next`
  --> return-local-binding-from-desugaring.rs:LL:CC
   |
LL |     for ref x in xs {
   |         ----- `__next` is borrowed here
...
LL |     result
   |     ^^^^^^ returns a value referencing data owned by the current function
```

Ideally `LocalKind` would carry more information to more accurately explain the problem, but for now, in order to avoid the ICE (fix rust-lang#63026), we accept `LocalKind::Var` without a name and produce the following output:

```
error[E0515]: cannot return value referencing local binding
  --> $DIR/return-local-binding-from-desugaring.rs:30:5
   |
LL |     for ref x in xs {
   |                  -- local binding introduced here
...
LL |     result
   |     ^^^^^^ returns a value referencing data owned by the current function
```

…ttmcm

In which we constantly improve the Vec(Deque) array PartialEq impls

Use the same approach as in rust-lang#62435 as sanctioned by rust-lang#61415 (comment).

r? @scottmcm

Add test for issue-50900

Closes rust-lang#50900

…albini

Allow rustbot to add `F-*` + `requires-nightly`.

r? @pietroalbini