Destructurable data type using getAt() to associate a result with an object in a service method call

Destructurable.groovy

class Destructurable<E> {
    E obj
    Boolean result
    
    def getAt(idx) {
        if (idx == 0) return obj
        if (idx == 1) return result
        throw new RuntimeException("Only two parameters are returnable")
    }
}

User.groovy

class User {
    String email
    String password
    
    boolean save() {
        if (!email || !password) {
            return false
        }
        return true
    }
}

UserScript.groovy

def userService = new UserService()

def (user, success) = userService.register("dan.i.el.p.woods@gmail.com", null)
assert !success

(user, success) = userService.register("dan.i.el.p.woods@gmail.com", "1234")
assert success

UserService.groovy

class UserService {
    Destructurable<User> register(email, password) {
        def user = new User(email: email, password: password)
        def result = true
        if (!user.save()) {
            result = false
        }
        return [obj: user, result: result] as Destructurable<User>
    }
}