RFR: 8199149: Improve the exception message thrown by VarHandle of unsupported operation [v3]

[Chen Liang]

On Wed, 19 Jul 2023 23:48:03 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> `VarForm::getMemberName` currently throws UOE with no information if the requested access mode is unsupported.   To provide the var handle information, move the access mode check to `VarHandle` so that the exception message can include the var handle information.  Changes include:
>> 
>> 1. change `VarHandle::checkAccessModeThenIsDirect` to check if the access mode is unsupported.  This check is only needed for direct var handle.
>> 2. change `VarHandle::getMethodHandleUncached` to call `getMemberNameOrNull` and throw UOE with an informative exception message if the access mode is unsupported
>> 
>> The error message looks like:
>> 
>> java.lang.UnsupportedOperationException: compareAndSet is not supported for VarHandle[varType=java.lang.String, coord=[class Foo$Goo]]
>
> Mandy Chung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review feedback from psandoz

The enum values caching can be applied to `AccessType` as well; can be done in a separate patch, and I've created ticket at https://bugs.openjdk.org/browse/JDK-8312423.

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Marked as reviewed by liach (Author).

PR Review: https://git.openjdk.org/jdk/pull/14928#pullrequestreview-1538211524