Fix assert hit when tree-transforming template template parameter packs.

[klimek]

Summary

Covers significantly more code in the template template pack argument
test and fixes the resulting assert problem.

[dblaikie]

test/SemaTemplate/temp_arg_template.cpp

80 ↗

(On Diff #43523)

It would be good if we tested for some specific behavior here other than "don't crash" (doing anything other than crashing is a bit underspecified) - maybe we should be testing that N has the right value?

(don't have quite enough context on the fix itself to sign off on it though, unfortunately :/)

[klimek]

Expand test.

[klimek]

test/SemaTemplate/temp_arg_template.cpp

80 ↗

(On Diff #43523)

Done.

[bkramer]

This looks good. getAsTemplateOrTemplatePattern mirrors the existing switch in TreeTransform.

cfe/trunk/lib/Sema/TreeTransform.h

case TemplateArgument::Type:
     Output = TemplateArgumentLoc(Arg,
                SemaRef.Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
 
     break;
 
   case TemplateArgument::Template:
   case TemplateArgument::TemplateExpansion: {
     NestedNameSpecifierLocBuilder Builder;
-    TemplateName Template = Arg.getAsTemplate();
+    TemplateName Template = Arg.getAsTemplateOrTemplatePattern();
     if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
       Builder.MakeTrivial(SemaRef.Context, DTN->getQualifier(), Loc);
     else if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
       Builder.MakeTrivial(SemaRef.Context, QTN->getQualifier(), Loc);
 
     if (Arg.getKind() == TemplateArgument::Template)
       Output = TemplateArgumentLoc(Arg,
                                    Builder.getWithLocInContext(SemaRef.Context),

cfe/trunk/test/SemaTemplate/temp_arg_template.cpp

struct unbox_args {
   typedef typename Primitive::template call<F> x;
 };
 
 template <template <typename> class... Templates>
 #if __cplusplus <= 199711L
 // expected-warning@-2 {{variadic templates are a C++11 extension}}
 #endif
 
-struct template_tuple {};
+struct template_tuple {
+#if __cplusplus >= 201103L
+  static constexpr int N = sizeof...(Templates);
+#endif
+};
 template <typename T>
 struct identity {};
 template <template <typename> class... Templates>
 #if __cplusplus <= 199711L
 // expected-warning@-2 {{variadic templates are a C++11 extension}}
 #endif
 
 template_tuple<Templates...> f7() {}
 
+#if __cplusplus >= 201103L
+struct S : public template_tuple<identity, identity> {
+  static_assert(N == 2, "Number of template arguments incorrect");
+};
+#endif
+
 void foo() {
   f7<identity>();
 }