RFR: 8282080: Lambda deserialization fails for Object method references on interfaces [v2]

[Joe Darcy]

On Thu, 28 Apr 2022 18:36:48 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> Per JLS, every interface with no superinterfaces implicitly has all public methods `java.lang.Object` has (unless the interface declares them explicitly). So, having:
>> 
>> interface I {}
>> 
>> the interface has methods like `hashCode()`. But, before https://bugs.openjdk.java.net/browse/JDK-8272564, javac was referring to them as if they were a `java.lang.Object` methods, not the interface methods. E.g. saying `I i = null; i.hashCode()` lead to a reference to `java.lang.Object.hashCode()` not `I.hashCode()`. That was changed in JDK-8272564, and now the reference is to `I.hashCode()`.
>> 
>> There is one issue, though: when the reference is for a serializable (and serialized) method handle, the runtime method is still `java.lang.Object::hashCode`, but the deserialization code generated by javac expects `I::hashCode`, and hence the serialized method handle fails to deserialize.
>> 
>> The proposal here is to fix just this case, by changing the deserialization code to expect the method from `java.lang.Object`, which should revert the deserialization behavior back to JDK 17 behavior.
>
> Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Avoiding a use of a new flag to determine Object methods copied to interfaces.

Please file a CSR for the behavioral compatibility impact.

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PR: https://git.openjdk.java.net/jdk/pull/8054