I think the initial version of r293172 was trying:
std::forward<Args...>(args)...
which doesn't compile. This seems like the correct way:
std::forward<Args>(args)...
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293214 91177308-0d34-0410-b5e6-96231b3b80d8