When parsing typename specifiers (with either the identifier or
simple-template-id form), check whether the scope specifier is
computable as a declaration context rather than checking whether it is
dependent, so that we properly cope with members of the current
instantiation. 

Improve testing for typename specifiers that terminate in a
simpe-template-id.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@80783 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed