Implement support for null non-type template arguments for non-type
template parameters of pointer, pointer-to-member, or nullptr_t
type in C++11. Fixes PR9700 / <rdar://problem/11193097>.

llvm-svn: 154219
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 15f85ba..acf5e0b 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -3313,8 +3313,11 @@
     case TemplateArgument::Expression:
       return Arg;
 
-    case TemplateArgument::Declaration:
-      return TemplateArgument(Arg.getAsDecl()->getCanonicalDecl());
+    case TemplateArgument::Declaration: {
+      if (Decl *D = Arg.getAsDecl())
+          return TemplateArgument(D->getCanonicalDecl());
+      return TemplateArgument((Decl*)0);
+    }
 
     case TemplateArgument::Template:
       return TemplateArgument(getCanonicalTemplateName(Arg.getAsTemplate()));