RFR: 8369654: javac OutOfMemoryError for complex intersection type [v7]

[Vicente Romero]

On Fri, 31 Oct 2025 17:28:48 GMT, Vicente Romero <vromero at openjdk.org> wrote:

>> Javac is throwing an OOME for the code like:
>> 
>> class Test {
>>     interface WithMixin01<T> {}
>>     // ...
>>     // 20 interfaces here
>>     interface WithMixin20<T> {}
>> 
>>     interface ClientA extends
>>             WithMixin02<ClientA>,
>>             WithMixin01<ClientA>,
>>             WithMixin03<ClientA>,
>>             WithMixin04<ClientA>,
>>             WithMixin05<ClientA>,
>>             WithMixin06<ClientA>,
>>             WithMixin07<ClientA>,
>>             WithMixin08<ClientA>,
>>             WithMixin09<ClientA>,
>>             WithMixin10<ClientA>,
>>             WithMixin11<ClientA>,
>>             WithMixin12<ClientA>,
>>             WithMixin13<ClientA>,
>>             WithMixin14<ClientA>,
>>             WithMixin15<ClientA>,
>>             WithMixin16<ClientA>,
>>             WithMixin17<ClientA>,
>>             WithMixin18<ClientA>,
>>             WithMixin19<ClientA>,
>>             WithMixin20<ClientA> {
>>     }
>> 
>>     interface ClientB extends
>>             WithMixin01<ClientB>,
>>             WithMixin02<ClientB>,
>>             WithMixin03<ClientB>,
>>             WithMixin04<ClientB>,
>>             WithMixin05<ClientB>,
>>             WithMixin06<ClientB>,
>>             WithMixin07<ClientB>,
>>             WithMixin08<ClientB>,
>>             WithMixin09<ClientB>,
>>             WithMixin10<ClientB>,
>>             WithMixin11<ClientB>,
>>             WithMixin12<ClientB>,
>>             WithMixin13<ClientB>,
>>             WithMixin14<ClientB>,
>>             WithMixin15<ClientB>,
>>             WithMixin16<ClientB>,
>>             WithMixin17<ClientB>,
>>             WithMixin18<ClientB>,
>>             WithMixin19<ClientB>,
>>             WithMixin20<ClientB> {
>>     }
>> 
>>     public static void main(String... args) {
>>         ClientA a = null;
>>         ClientB b = null;
>>         String selector = "a";
>>         Object o = switch (selector) {
>>             case "a" -> a;
>>             case "b" -> b;
>>             default -> null;
>>         };
>>     }
>> }
>> 
>> the reason is that after [JDK-8353565](https://bugs.openjdk.org/browse/JDK-8353565) we are using Types::lub when joining jump chains in Code. The result of the lub will be erased anyways so the proposal here is to cut in the result given by lub types that will be erased anyways. The reason for the slow lub invocation here is that in order to obtain the lub in this case, the lub method is invoked several times. Each invocation, minus the first one, with very complex types which makes them very ...
>
> Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:
> 
>   adding more array support

I have updated the PR improving the array support, basically the previous approach was arriving to a wrong supertype for the case of two reference arrays. There is now some code that is common to a portion of lub which we could probably extract to a common method in Types and just reuse it in Code but not without some massage anyways that could slow the general lub a bit so probably not worthy as lub is a very established code that I don't think will change in the near future. Thanks for all the comments so far

-------------

PR Comment: https://git.openjdk.org/jdk/pull/28050#issuecomment-3474119310