fn with_optional_delta(base int, delta ?int) int {
    actual_delta := delta or { 0 }
    return base + actual_delta
}

fn optional_only(value ?int) int {
    return value or { -1 }
}

struct OptionalGreeter {}

fn (_ OptionalGreeter) add(base int, delta ?int) int {
    return with_optional_delta(base, delta)
}

type OptionalGreeterFn = fn (int, ?int) int

fn test_trailing_optional_params_can_be_omitted_in_free_function_calls() {
    assert with_optional_delta(5) == 5
    assert with_optional_delta(5, 2) == 7
    assert optional_only() == -1
    assert optional_only(8) == 8
}

fn test_trailing_optional_params_can_be_omitted_in_method_calls() {
    greeter := OptionalGreeter{}
    assert greeter.add(5) == 5
    assert greeter.add(5, 2) == 7
}

fn test_trailing_optional_params_can_be_omitted_in_fn_variable_calls() {
    handler := OptionalGreeterFn(with_optional_delta)
    assert handler(5) == 5
    assert handler(5, 2) == 7
}