`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]] ------------- Commit messages: - 8199149: Improve the exception message thrown by VarHandle of unsupported operation Changes: https://git.openjdk.org/jdk/pull/14928/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14928&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8199149 Stats: 35 lines in 3 files changed: 31 ins; 0 del; 4 mod Patch: https://git.openjdk.org/jdk/pull/14928.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/14928/head:pull/14928 PR: https://git.openjdk.org/jdk/pull/14928
