[clang] [ObjC] Enable diagnose_if on Objective-C methods (PR #115056)

[Akira Hatanaka via cfe-commits]

ahatanak wrote:

> There is almost certainly value in introducing a base class beneath ObjCMethodDecl and FunctionDecl that is both a NamedDecl and a DeclContext, because I'm not the first person to run into this problem. If I do the work, whose review/approval do we need? Is it deep enough in the guts of clang that it will take an RFC or is it something that we can reasonably thumbs-up in a PR?

@AaronBallman @rjmccall any thoughts?


https://github.com/llvm/llvm-project/pull/115056