Teach TreeTransform how to transform a pack expansion type into
another pack expansion type. This can happen when rebuilding types in
the current instantiation.

Fixes <rdar://problem/8848837> (Clang crashing on libc++ <functional>).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123316 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed