[clang] [clang-tools-extra] [libcxx] [clang] improved preservation of template keyword (PR #133610)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

We're seeing another problem after this commit: seemingly bogus `class member cannot be redeclared` errors. I'll try to provide a reduced repro on Monday.

https://github.com/llvm/llvm-project/pull/133610