PR c++/53540 - using fails to be equivalent to typedef

In the example of this problem report, during the substituting of int
into 'function', tsubst_aggr_type fails for the alias ctxt1.  This is
because TYPE_TEMPLATE_INFO looks for the TEMPLATE_INFO of the ctxt1
alias at the wrong place and was wrongly finding it to be NULL.
Namely, it was looking for it in the DECL_TEMPLATE_INFO of the
declaration of the type -- as if ctxt1 was an alias template
specialization -- rather than looking for it in its
CLASSTYPE_TEMPLATE_INFO.

Fixed thus.  The other hunks of the patch are a cleanup to make a
better use of alias_template_specialization_p.

Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp

	* cp-tree.h (TYPE_TEMPLATE_INFO): For an alias that is not an
	instance of alias template, don't look for its TEMPLATE_INFO in
	its declaration.
	(alias_template_specialization_p): Take const_tree.
	* pt.c (alias_template_specialization_p): Take a const_tree.
	Don't call primary_template_instantiation_p.
	(primary_template_instantiation_p): Call
	alias_template_specialization_p.

gcc/testsuite/

	* g++.dg/cpp0x/alias-decl-24.C: New test.

From-SVN: r192304

gcc/cp/ChangeLog

+2012-10-09  Dodji Seketeli  <dodji@redhat.com>
+
+	PR c++/53540 - using fails to be equivalent to typedef
+	* cp-tree.h (TYPE_TEMPLATE_INFO): For an alias that is not an
+	instance of alias template, don't look for its TEMPLATE_INFO in
+	its declaration.
+	(alias_template_specialization_p): Take const_tree.
+	* pt.c (alias_template_specialization_p): Take a const_tree.
+	Don't call primary_template_instantiation_p.
+	(primary_template_instantiation_p): Call
+	alias_template_specialization_p.
+
 2012-10-10  Dodji Seketeli  <dodji@redhat.com>
 
 	* parser (cp_parser_statement): Parse c++11 attributes

gcc/cp/cp-tree.h

@@ -2646,8 +2646,8 @@ extern void decl_shadowed_for_var_insert (tree, tree);
    template info for the alias template, not the one (if any) for the
    template of the underlying type.  */
 #define TYPE_TEMPLATE_INFO(NODE)					\
-  (TYPE_ALIAS_P (NODE)							\
-   ? ((TYPE_NAME (NODE) && DECL_LANG_SPECIFIC (TYPE_NAME (NODE)))	\
+  ((TYPE_ALIAS_P (NODE) && DECL_LANG_SPECIFIC (TYPE_NAME (NODE)))	\
+   ? (DECL_LANG_SPECIFIC (TYPE_NAME (NODE))				\
       ? DECL_TEMPLATE_INFO (TYPE_NAME (NODE))				\
       : NULL_TREE)							\
    : ((TREE_CODE (NODE) == ENUMERAL_TYPE)				\
@@ -5437,7 +5437,7 @@ extern bool reregister_specialization		(tree, tree, tree);
 extern tree fold_non_dependent_expr		(tree);
 extern tree fold_non_dependent_expr_sfinae	(tree, tsubst_flags_t);
 extern bool alias_type_or_template_p            (tree);
-extern bool alias_template_specialization_p     (tree);
+extern bool alias_template_specialization_p     (const_tree);
 extern bool explicit_class_specialization_p     (tree);
 extern int push_tinst_level                     (tree);
 extern void pop_tinst_level                     (void);

gcc/cp/pt.c

@@ -2929,10 +2929,7 @@ primary_template_instantiation_p (const_tree t)
   else if (CLASS_TYPE_P (t) && !TYPE_DECL_ALIAS_P (TYPE_NAME (t)))
     return CLASSTYPE_TEMPLATE_INSTANTIATION (t)
 	   && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (t));
-  else if (TYPE_P (t)
-	   && TYPE_TEMPLATE_INFO (t)
-	   && PRIMARY_TEMPLATE_P (TYPE_TI_TEMPLATE (t))
-	   && DECL_TEMPLATE_INSTANTIATION (TYPE_NAME (t)))
+  else if (alias_template_specialization_p (t))
     return true;
   return false;
 }
@@ -5077,11 +5074,14 @@ alias_type_or_template_p (tree t)
 /* Return TRUE iff is a specialization of an alias template.  */
 
 bool
-alias_template_specialization_p (tree t)
+alias_template_specialization_p (const_tree t)
 {
   if (t == NULL_TREE)
     return false;
-  return (primary_template_instantiation_p (t)
+  
+  return (TYPE_P (t)
+	  && TYPE_TEMPLATE_INFO (t)
+	  && PRIMARY_TEMPLATE_P (TYPE_TI_TEMPLATE (t))
 	  && DECL_ALIAS_TEMPLATE_P (TYPE_TI_TEMPLATE (t)));
 }
 
@@ -10945,10 +10945,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
     {
       tree decl = TYPE_NAME (t);
 
-      if (TYPE_DECL_ALIAS_P (decl)
-	  && DECL_LANG_SPECIFIC (decl)
-	  && DECL_TEMPLATE_INFO (decl)
-	  && PRIMARY_TEMPLATE_P (DECL_TI_TEMPLATE (decl)))
+      if (alias_template_specialization_p (t))
 	{
 	  /* DECL represents an alias template and we want to
 	     instantiate it.  */

gcc/testsuite/ChangeLog

+2012-10-09  Dodji Seketeli  <dodji@redhat.com>
+
+	PR c++/53540 - using fails to be equivalent to typedef
+	* g++.dg/cpp0x/alias-decl-24.C: New test.
+
 2012-10-10  Dodji Seketeli  <dodji@redhat.com>
 
 	* g++.dg/cpp0x/gen-attrs-8.C: Update the test to reflect the fact

gcc/testsuite/g++.dg/cpp0x/alias-decl-24.C

+// Origin: PR c++/53540
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct context
+{
+  typedef int type;
+};
+
+template <typename T>
+void function()
+{
+  using ctx1 = context<T>;
+  typename ctx1::type f1;
+
+  typedef context<T> ctx2;
+  typename ctx2::type f2;
+}
+
+int main()
+{
+  function<int>();
+}
+