c++: alias template of non-template class [PR112633]

The entering_scope adjustment in tsubst_aggr_type assumes if an alias is
dependent, then so is the aliased type (and therefore it has template info)
but that's not true for the dependent alias template specialization ty1<T>
below which aliases the non-template class A.  In this case no adjustment
is needed anyway, so we can just punt.

	PR c++/112633

gcc/cp/ChangeLog:

	* pt.cc (tsubst_aggr_type): Handle empty TYPE_TEMPLATE_INFO
	in the entering_scope adjustment.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/alias-decl-75.C: New test.

gcc/cp/pt.cc

@@ -13976,6 +13976,7 @@ tsubst_aggr_type (tree t,
       if (entering_scope
 	  && CLASS_TYPE_P (t)
 	  && dependent_type_p (t)
+	  && TYPE_TEMPLATE_INFO (t)
 	  && TYPE_CANONICAL (t) == TREE_TYPE (TYPE_TI_TEMPLATE (t)))
 	t = TYPE_CANONICAL (t);
 

gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C

@@ -0,0 +1,13 @@
+// PR c++/112633
+// { dg-do compile { target c++11 } }
+
+struct A { using type = void; };
+
+template<class>
+using ty1 = A;
+
+template<class T>
+using ty2 = typename ty1<T>::type;
+
+template<class T>
+ty2<T> f();