struct Decoder {}

pub fn decode[T](val string) !T {
    mut decoder := Decoder{}
    mut result := T{}
    decoder.decode_value(mut result)!
    return result
}

fn (mut decoder Decoder) decode_value[T](mut val T) ! {
    $if T.unaliased_typ is $array {
        decoder.decode_array(mut val)!
        return
    } $else $if T is $option {
        val = none
    }
}

fn (mut decoder Decoder) decode_array[T](mut val []T) ! {
    $if T is $option {
        val << none
        val << 1
    } $else {
        val << 1
    }

    mut array_element := T{}
    decoder.decode_value(mut array_element)!
    val << array_element
}

fn test_main() {
    assert decode[[]int]('')! == [1, 0]
    x := decode[[]?int]('')!
    assert x[0] == ?int(none)
    assert x[1] == ?int(1)
    assert x[2] == none
}