pub struct Two_data {
pub mut:
    title   string
    content string
}

pub struct Page {
pub mut:
    lang      string
    page      string
    var_one   string
    var_two   string
    var_three Two_data
}

fn get_keys_and_values[T](mut keys []string, mut values []string, mut data T) ([]string, []string, T) {
    $for field in T.fields {
        $if field.typ is string {
            keys << field.name
            values << data.$(field.name)
        }
    }
    return keys, values, data
}

fn awesome[T](mut data T) {
    mut keys := []string{}
    mut values := []string{}
    keys, values, data = get_keys_and_values(mut keys, mut values, mut data)
    println(keys)
    assert keys == ['lang', 'page', 'var_one', 'var_two']
    println(values)
    assert values == ['vlang', 'one', 'variable one', 'variable two']
    println(data)
    assert '${data}'.contains("title: 'what a title'")
}

fn test_generic_fn_infer_multi_paras() {
    mut page := Page{
        lang:      'vlang'
        page:      'one'
        var_one:   'variable one'
        var_two:   'variable two'
        var_three: Two_data{
            title:   'what a title'
            content: 'what a content'
        }
    }
    awesome(mut page)
}