fn test_optional(fail bool) ?string {
	if fail {
		return error('false')
	}
	return 'fff'
}

fn main() {
	// a := test_optional(false) or { println(err) }
	test_optional(true) or {
		// must be of the same type of the return
		// type of the `test_optional` function
		123
		// 'I break things'
	}
}