tests/ui/mismatched_types/closure-mismatch.rs

trait Foo {}

impl<T: Fn(&())> Foo for T {}

fn baz<T: Foo>(_: T) {}

fn main() {
    baz(|_| ());
    //~^ ERROR implementation of `FnOnce` is not general enough
    //~| ERROR implementation of `Fn` is not general enough
    baz(|x| ());
    //~^ ERROR implementation of `FnOnce` is not general enough
    //~| ERROR implementation of `Fn` is not general enough
}