When recursively instantiating function templates, keep track of the
instantiation stack so that we provide a full instantiation
backtrace. Previously, we performed all of the instantiations implied
by the recursion, but each looked like a "top-level" instantiation.

The included test case tests the previous fix for the instantiation of
DeclRefExprs. Note that the "instantiated from" diagnostics still
don't tell us which template arguments we're instantiating with.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74540 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed