llvm-project

03d04497 - [ADT] Use a dedicated empty type for StringSet (NFC) (#165967)

[ADT] Use a dedicated empty type for StringSet (NFC) (#165967) This patch introduces StringSetTag, a dedicated empty struct to serve as the "value type" for llvm::StringSet. This change is part of an effort to reduce the use of std::nullopt_t outside the context of std::optional.