[PATCH] cpp11-migrate: Fix crash in AddOverride due to template instantiations (PR15827)

[Edwin Vane]

  The important difference is the template arg is not used in the base class specifier. If you can't alter the inheritance of the class then we know when it's safe to add override. The non-risky example you gave is still possibly risky since that template arg might be provided to the base class which may use that arg to alter **it's** inheritance. That is the problem has just been moved up the inheritance chain.

  I think with a bit of extra work we can fix this revision to just check for template arg dependence in the base class specifier. If so, don't transform. If not, transform away.

  Then the only XFAIL we have is that pure specifier case. Feel free to log an enhancement against clang to get the source location for the pure specifier recorded.

http://llvm-reviews.chandlerc.com/D769