Merge #986

Merge #986

986: Fix parse tree of attribute on match arm r=matklad a=pcpthm

```rust
match () {
    #[attr]
    () => (),
}
```
Incorrect parse tree: `MatchArmList(Attr(..), MatchArm(..))`.
Fixed: `MatchArmList(MatchArm(Attr(..), ...))`.

Co-authored-by: pcpthm <pcpthm@gmail.com>