[clang] [clang][Sema] Ignore the parentheses in the guard of DiagnoseUnexpandedParameterPack (PR #86401)

[David Blaikie via cfe-commits]

dwblaikie wrote:

Yep, the original code still crashes with this PR applied, and the reduced test case comes down to something identical to the code shown in https://github.com/llvm/llvm-project/pull/86401#issuecomment-2024151742 with a stack trace that looks the same as the one caused by the test case this patch is addressing.

I tend to think this patch is insufficiently general - that there's any number of ways an unexpanded pack could appear inside an expression and ignoring parens is only one fairly narrow case of a broader issue?

https://github.com/llvm/llvm-project/pull/86401