rustc/tests/ui/traits/safety-fn-body.rs

// Check that an unsafe impl does not imply that unsafe actions are
// legal in the methods.

unsafe trait UnsafeTrait : Sized {
    fn foo(self) { }
}

unsafe impl UnsafeTrait for *mut isize {
    fn foo(self) {
        // Unsafe actions are not made legal by taking place in an unsafe trait:
        *self += 1;
        //~^ ERROR E0133
    }
}

fn main() { }