[clang] [Clang] Disallow explicit object parameters irrespective of whether return type is valid (PR #174603)

[via cfe-commits]

Sirraide wrote:

> Next time your summary needs to explain how you are fixing the problem and explain why it is correct.
> 
> The diff makes it tricky to see what changed and explaining more details in the summary would speed up review. Reviewers is very precious and a good summary is important to making code review more effective.
> 
> CC @Sirraide

Ah, yeah, that’s partly on me; I had to edit this particular part of the codebase not too long ago, so it didn’t occur to me that this change might not be obvious

https://github.com/llvm/llvm-project/pull/174603