PR c++/77339 - ICE with invalid use of alias template.

	* pt.c (lookup_template_class_1): Don't try to enter the scope of an
	alias template.

From-SVN: r246462

gcc/cp/ChangeLog

+2017-03-24  Jason Merrill  <jason@redhat.com>
+
+	PR c++/77339 - ICE with invalid use of alias template.
+	* pt.c (lookup_template_class_1): Don't try to enter the scope of an
+	alias template.
+
 2017-03-24  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/80119

gcc/cp/pt.c

@@ -8682,9 +8682,9 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
 	  || !PRIMARY_TEMPLATE_P (gen_tmpl)
 	  || currently_open_class (template_type))
 	{
-	  tree tinfo = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (template_type);
+	  tree tinfo = TYPE_TEMPLATE_INFO (template_type);
 
-	  if (comp_template_args (TI_ARGS (tinfo), arglist))
+	  if (tinfo && comp_template_args (TI_ARGS (tinfo), arglist))
 	    return template_type;
 	}
 

gcc/testsuite/g++.dg/cpp0x/alias-decl-58.C

+// PR c++/77339
+// { dg-do compile { target c++11 } }
+
+template < typename > using A = int;
+
+//OK: template < typename X > A < X > a; 
+template < typename X > A < X >::a; // { dg-error "" }