struct MyStruct[T] {
    arr []T
}

fn (mut s MyStruct[T]) get_data(pos int) T {
    return s.arr[pos]
}

fn (mut s MyStruct[T]) iterate(handler fn (T) int) int {
    mut sum := 0
    mut i := 0
    for {
        k := s.get_data[T](i)
        sum += handler(k)
        i++
        if i > 4 {
            break
        }
    }
    return sum
}

pub fn consume(data int) int {
    return data
}

pub fn consume_str(data string) string {
    return data
}

fn call[T](f fn (T) T, v T) T {
    return f(v)
}

struct Pair[T, U] {
    a T
    b U
}

fn test_generics_with_anon_generics_fn() {
    mut s := MyStruct[int]{
        arr: [1, 2, 3, 4, 5]
    }
    y := s.iterate[int](consume)
    println(y)
    assert y == 15

    assert call[int](consume, 1) == 1
    assert call[string](consume_str, '1') == '1'
    assert call(consume, 1) == 1
    assert call(consume_str, '1') == '1'

    pair := Pair[int, string]{1, 's'}
    assert call(fn (v Pair[int, string]) Pair[int, string] {
        return v
    }, pair) == pair
}