attributes on binary expressions trigger `unused_parens` lint

[oli-obk]

Yes the following code is pointless, but I needed any attribute to reproduce, so I chose a derive

#![feature(stmt_expr_attributes)]

fn main() {
    let x = #[derive(Foo)](5 + 6);
}

produces

warning: unnecessary parentheses around assigned value
 --> src/main.rs:4:27
  |
4 |     let x = #[derive(Foo)](5 + 6);
  |                           ^^^^^^^
  |
  = note: #[warn(unused_parens)] on by default