[clang] [clang][Sema] Fix false-positive -Wshadow for friend functions (PR #221249)

[Shengxin Pei via cfe-commits]

TPPPP72 wrote:

> Careful, I think this fix drops some true-positive -Wshadow warnings as well. 
> When I test this example in the PR, the warning is gone.


Oh, thank you for pointing out. Fortunately we haven't merged this.

https://github.com/llvm/llvm-project/pull/221249