[clang] [Sema] Diagnose use of if/else-if condition variable inside else-if/else branch(s) (PR #156436)

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arrowten wrote:

@Alcaro 

> I agree the worst case would be bad; if I'm reading things correctly, it'd be quadratic for things like

Any specific code changes you want to suggest?

https://github.com/llvm/llvm-project/pull/156436