1848: Parse `..` as a full pattern r=matklad a=ecstatic-morse
Resolves#1479.
This PR implements [RFC 2707](https://github.com/rust-lang/rfcs/pull/2707) in the parser. It introduces a new `DotDotPat` AST node modeled on `PlaceholderPat` and changes the parsing of tuple and slice patterns to conform to the RFC.
Notably, this PR does *not* change the resulting AST when `..` appears in a struct pattern (e.g. `Struct { a, b: c, .. }`). I *think* this is the behavior mandated by RFC 2707, but someone should confirm this.
Co-authored-by: Dylan MacKenzie <ecstaticmorse@gmail.com>
1661: Parse function parameters attributes r=matklad a=eupn
Fixes#1397. The [RFC-2565](https://github.com/rust-lang/rfcs/blob/master/text/2565-formal-function-parameter-attributes.md) specifies `#[attributes]` to function parameters:
```rust
fn foo(#[attr] a, #[unused] b, #[must_use] ...) {
// ...
}
```
This PR adds those attributes into grammar and to the parser, extending corresponding inline tests.
Co-authored-by: Evgenii P <eupn@protonmail.com>
