[clang] [Sema] Reject unqualified lookup of local nested class name (PR #192678)

[via cfe-commits]

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arrowten wrote:

@zwuis This tells the compiler it has to ignore the names which belong inside a class, like A::B when you are searching from outside the class. So when you use B, the compiler cannot find A::B and the lookup fails.

https://github.com/llvm/llvm-project/pull/192678