rust/tests/ui/let_underscore_future.rs

use std::future::Future;
//@no-rustfix
async fn some_async_fn() {}

fn sync_side_effects() {}
fn custom() -> impl Future<Output = ()> {
    sync_side_effects();
    async {}
}

fn do_something_to_future(future: &mut impl Future<Output = ()>) {}
//~^ ERROR: this argument is a mutable reference, but not used mutably
//~| NOTE: `-D clippy::needless-pass-by-ref-mut` implied by `-D warnings`

fn main() {
    let _ = some_async_fn();
    //~^ ERROR: non-binding `let` on a future
    let _ = custom();
    //~^ ERROR: non-binding `let` on a future

    let mut future = some_async_fn();
    do_something_to_future(&mut future);
    let _ = future;
    //~^ ERROR: non-binding `let` on a future
}