use std::borrow::Borrow;

pub trait IntoIterExt: IntoIterator {
    fn contains_any_of<U>(self, other: U) -> bool where Self::Item: PartialEq,
                                                        U: IntoIterator,
                                                        U::Item: Borrow<Self::Item>;
}

impl<T: IntoIterator> IntoIterExt for T {
    fn contains_any_of<U>(self, _other: U) -> bool where Self::Item: PartialEq,
                                                         U: IntoIterator,
                                                         U::Item: Borrow<Self::Item> {
        true
    }
}

#[test]
fn contains_empty_coll_contains_empty_vec_yields_true() {
    // given an empty collection
    let coll = Vec::<i32>::new();

    // when `contains()` invoked with `Vec` empty set
    let result = coll.contains_any_of(Vec::<i32>::new());

    // then the result should be true
    assert_eq!(true, result);
}

#[test]
fn contains_empty_coll_contains_empty_slice_yields_true() {
    // given an empty collection
    let coll = Vec::<i32>::new();

    // when `contains()` invoked with `slice` empty set
    let result = coll.contains_any_of(&[]);

    // then the result should be true
    assert_eq!(true, result);
}