Add a missing ExpressionEvaluationContext for template default arguments.  Fixes PR12581.

llvm-svn: 155670
diff --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index f8204d9..5c3e2ba 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -652,6 +652,7 @@
     //   end of the template-parameter-list rather than a greater-than
     //   operator.
     GreaterThanIsOperatorScope G(GreaterThanIsOperator, false);
+    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
 
     DefaultArg = ParseAssignmentExpression();
     if (DefaultArg.isInvalid())