Introduce a new expression kind, SubstNonTypeTemplateParmPackExpr,
that captures the substitution of a non-type template argument pack
for a non-type template parameter pack within a pack expansion that
cannot be fully expanded. This follows the approach taken by
SubstTemplateTypeParmPackType.

llvm-svn: 123506
diff --git a/clang/lib/AST/ExprClassification.cpp b/clang/lib/AST/ExprClassification.cpp
index a9ebe6f..c9f4fa8 100644
--- a/clang/lib/AST/ExprClassification.cpp
+++ b/clang/lib/AST/ExprClassification.cpp
@@ -152,6 +152,7 @@
   case Expr::ParenListExprClass:
   case Expr::InitListExprClass:
   case Expr::SizeOfPackExprClass:
+  case Expr::SubstNonTypeTemplateParmPackExprClass:
     return Cl::CL_PRValue;
 
     // Next come the complicated cases.