[llvm] Improve diagnostic for malformed constant vectors (PR #216253)

[via llvm-commits]

zhangweize9-cyber wrote:

> Hi @zhangweize9-cyber a gentle ping on this PR when you have a moment... No rush, just wanted to make sure it didnt drop off the radar 😄... Thanks

Write your conditional logic in the `case lltok::APSInt` conditional branch under the `parseValID` function. The approach is correct, but the conditional branch needs fine-tuning.

https://github.com/llvm/llvm-project/pull/216253