impl Parse for ExprArray

[dtolnay]

ExprArray can be parsed directly rather than going through impl_by_parsing_expr. This makes the following type of thing possible:

let x: ExprArray = input.parse()?;
let _: Token![+] = input.parse()?;
let y: ExprArray = input.parse()?;

which previously would have failed due to the + being eagerly consumed as part of x, making it into ExprBinary, and thereby failing to parse x as ExprArray.