Question about JEP 406

[Remi Forax]

It can be reduced to

  sealed interface Exp<T> { }
  record Add() implements Exp<Integer> {}
  record Lit<T>(T obj) implements Exp<T> {}

Yes, we have missed that case.

When a subtype of a sealed type is not a subtype of the type switch upon, it should be discarded when testing exhaustiveness.

Thanks,
Rémi

----- Mail original -----
> De: "Jim Laskey" <james.laskey at oracle.com>
> À: "amber-dev" <amber-dev at openjdk.java.net>
> Cc: "Tesla Ice Zhang" <ice1000kotlin at foxmail.com>
> Envoyé: Mardi 15 Juin 2021 18:59:39
> Objet: Re: Question about JEP 406

> [HTML messed up in original code]
> 
> sealed interface Exp<T> {
>  record Add(Exp<Integer> lhs, Exp<Integer> rhs) implements Exp<Integer> {}
>  record Lit<T>(T obj) implements Exp<T> {}
> }
> 
> 
>> On May 21, 2021, at 2:06 AM, Tesla Ice Zhang <ice1000kotlin at foxmail.com> wrote:
>> 
>> Hi OpenJDK developers,
>> 
>> I'm very excited about JEP 406. Sealed classes are taken into account in switch
>> expressions, which is great! However, there is one special case not mentioned
>> in the JEP, about generic sealed interfaces:
>> 
>> 
>> sealed interface Exp<T> {
>>  record Add(Exp<Integer> lhs, Exp<Integer> rhs) implements
>> Exp<Integer> {}
>>  record Lit<T>(T obj) implements Exp<T> {}
>> }
>> 
>> 
>> 
>> In the above example, if we do a switch on an expression of type
>> Exp<Boolean>, do we need to provide a case for Add?
>> 
>> 
>> Best regards,
> > Tesla