Enable it for USRs and names when indexing.
Forward references can have different template argument names; including them
makes USRs and names unstable, since the name depends on whether we saw a forward reference or not.
llvm-svn: 260866
These codepaths would generate warnings with GCC on linux even though the switch
was covered. Add llvm_unreachable markers to indicate that the switch should be
covered. NFC.
llvm-svn: 260865
Argyrios Kyrtzidis