4b362f152e
This came up in https://github.com/llvm/llvm-project/issues/155691. For `std::basic_string` our formatter matching logic required the allocator template parameter to be a `std::allocator`. There is no compelling reason (that I know of) why this would be required for us to apply the existing formatter to the string. We don't check the `allocator` parameter for other STL containers either. This meant that `std::string` that used custom allocators wouldn't be formatted. This patch relaxes the regex for `basic_string`.