rust/src/test/compile-fail/block-coerce-no-2.rs

// Make sure that fn-to-block coercion isn't incorrectly lifted over
// other tycons.

fn main() {
    fn f(f: extern fn(extern fn(extern fn()))) {
    }

    fn g(f: extern fn(fn())) {
    }

    f(g);
    //~^ ERROR mismatched types: expected `fn(fn(fn()))`
}