rustc/tests/ui/coroutine/drop-yield-twice.rs

#![feature(negative_impls, coroutines)]

struct Foo(i32);
impl !Send for Foo {}

fn main() {
    assert_send(|| { //~ ERROR coroutine cannot be sent between threads safely
        let guard = Foo(42);
        yield;
        drop(guard);
        yield;
    })
}

fn assert_send<T: Send>(_: T) {}