module main

struct Demo[T] {
mut:
    val T
}

type DemoType = int | []DemoType

fn test_main() {
    assert decode[Demo[[]DemoType]]() == Demo[[]DemoType]{}
    assert decode[Demo[DemoType]]() == Demo[DemoType]{}
}

fn decode[T]() T {
    mut typ := T{}
    typ.val = decode_x(typ.val)
    return typ
}

fn decode_x[T](_ T) T {
    mut field := T{}
    $if T is int {
        field = 0
    } $else $if T is $array {
        field = []DemoType{}
    }
    return field
}