`|| () as ()()` is no longer supposed to parse

[dtolnay]

fn main() {
    || () as ()();
}

This used to compile successfully in rustc versions 1.42.0 and older. It was parsed as (|| () as ())(). But since 1.43.0 it is no longer parsed by rustc: rust-lang/rust#68985.

error: casts cannot be followed by a function call
 --> src/main.rs:2:8
  |
2 |     || () as ()();
  |        ^^^^^^^^
  |
help: try surrounding the expression in parentheses
  |
2 |     || (() as ())();
  |        +        +