Fix crash while parsing variable template with variadic template arguments

It is only a crash if the compiler optimize for this!=nullptr because
LocalInstantiationScope::getPartiallySubstitutedPack checks if 'this' is null
(This is crashing when clang is compiled with GCC6)

Differential Revision: http://reviews.llvm.org/D20511

llvm-svn: 270845

2 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index 52a1ad545a5..06afe87f515 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -604,7 +604,7 @@ bool Sema::CheckParameterPacksForExpansion(
     //   Template argument deduction can extend the sequence of template 
     //   arguments corresponding to a template parameter pack, even when the
     //   sequence contains explicitly specified template arguments.
-    if (!IsFunctionParameterPack) {
+    if (!IsFunctionParameterPack && CurrentInstantiationScope) {
       if (NamedDecl *PartialPack 
                     = CurrentInstantiationScope->getPartiallySubstitutedPack()){
         unsigned PartialDepth, PartialIndex;
diff --git a/clang/test/SemaCXX/cxx1y-variable-templates_top_level.cpp b/clang/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
index 1e5c98beb9c..496ae888732 100644
--- a/clang/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
+++ b/clang/test/SemaCXX/cxx1y-variable-templates_top_level.cpp
@@ -458,3 +458,9 @@ namespace PR19169 {
   template<> int g<double>; // expected-error {{no variable template matches specialization; did you mean to use 'g' as function template instead?}}
 }
 
+#ifndef PRECXX11
+template <typename... Args> struct Variadic_t { };
+template <typename... Args> Variadic_t<Args...> Variadic;
+auto variadic1 = Variadic<>;
+auto variadic2 = Variadic<int, int>;
+#endif