src/test/ui/extern/extern-types-not-sync-send.rs

// Make sure extern types are !Sync and !Send.

#![feature(extern_types)]

extern {
    type A;
}

fn assert_sync<T: ?Sized + Sync>() { }
fn assert_send<T: ?Sized + Send>() { }

fn main() {
    assert_sync::<A>();
    //~^ ERROR `A` cannot be shared between threads safely [E0277]

    assert_send::<A>();
    //~^ ERROR `A` cannot be sent between threads safely [E0277]
}