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.unaliased_typ is $struct {
        $for field in T.fields {
            decoder.decode_value(mut val.$(field.name))!
        }
    }
}

fn (mut decoder Decoder) decode_array[T](mut val []T) ! {}

struct Foo {
    int  []int
    oint []?int
}

fn test_main() {
    decode[Foo]('')!
}