fn foo() ! {
    return error('something')
}

fn test_option_void() {
    foo() or {
        println(err)
        assert err.msg() == 'something'
        return
    }
}

fn bar() ! {
    return error('bar error')
}

fn test_option_void_only_question() {
    bar() or {
        println(err)
        assert err.msg() == 'bar error'
        return
    }
}

fn test_option_void_with_empty_or() {
    foo() or {}
    assert true
}

fn option_void(a int) ! {
    if a != 0 {
        return
    } else {
        return error('zero error')
    }
}

fn test_option_void_with_return() {
    option_void(0) or {
        println(err)
        assert err.msg() == 'zero error'
        return
    }
    option_void(-1) or {
        println(err)
        assert err.msg() == 'zero error'
        return
    }
    assert true
}

fn must_error_for_generic_result() ! {
    return error('boom')
}

fn never_returns_normally[T](value T) !T {
    must_error_for_generic_result()!
}

fn test_generic_result_propagation_from_always_error_fn_does_not_need_placeholder_return() {
    never_returns_normally(42) or {
        assert err.msg() == 'boom'
        return
    }
    assert false
}