rust-clippy/tests/ui/patterns.rs

#![feature(tool_lints)]

#![allow(unused)]
#![warn(clippy::all)]

fn main() {
    let v = Some(true);
    match v {
        Some(x) => (),
        y @ _   => (),
    }
    match v {
        Some(x)  => (),
        y @ None => (),  // no error
    }
}