RFR: 8208752: Calling a deserialized Lambda might fail with ClassCastException [v4]

[Jan Lahoda]

On Thu, 22 Jan 2026 11:45:08 GMT, Liam Miller-Cushon <cushon at openjdk.org> wrote:

>> See [JDK-8208752: Calling a deserialized Lambda might fail with ClassCastException](https://bugs.openjdk.org/browse/JDK-8208752).
>> 
>> Lambda deserialization currently does not consider `SerializedLambda#getInstantiatedMethodType` when deserializing lambdas, which can lead to method references that differ only in `getInstantiatedMethodType` being merged into the same lambda instance, and can result in `ClassCastException`s like the one reported in the bug.
>> 
>> This depends on the fix for [JDK-8374654: Inconsistent handling of lambda deserialization for Object method references on interfaces](https://bugs.openjdk.org/browse/JDK-8374654) in https://github.com/openjdk/jdk/pull/29075.
>
> Liam Miller-Cushon has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains nine commits:
> 
>  - Merge branch 'JDK-8374654' into JDK-8208752
>  - Test cleanup
>  - Updates for --debug=dumpLambdaDeserializationStats
>  - Merge branch 'JDK-8374654' into JDK-8208752
>  - Merge branch 'JDK-8374654' into JDK-8208752
>  - Update test
>  - Merge branch 'JDK-8374654' into JDK-8208752
>  - Don't rely on the iteration order of Map.of entries
>  - 8208752: Calling a deserialized Lambda might fail with ClassCastException

This looks reasonable to me, and I don't see how this could break anything (although that does not mean nothing will be broken, of course). Aside for making the method a bit bigger, of course, but that hopefully shouldn't be a big deal. So, overall, I am OK with this patch.

What I am not as OK with is the dependency on PR #29075 - that PR without this one will cause a regression, and even if it was a transient/short-term regression, I don't think we should knowingly do it.

So, my proposal would be to do one of these:
- change the order of the patches. Integrate this one (which should be OK, right?), and then PR #29075
- do both this and #29075 together

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

PR Comment: https://git.openjdk.org/jdk/pull/28943#issuecomment-3785329343