re PR c++/66850 (Adding a forward declaration of a template containing a template template parm causes ICE on valid code)

Fix PR c++/66850

gcc/cp/ChangeLog:

	PR c++/66850
	* pt.c (redeclare_class_template): Set the DECL_CONTEXTs of each
	template template parm in the redeclaration.
	(lookup_template_class_1): Peel off irrelevant template levels
	from current_template_parms before augmenting the argument
	list.

gcc/testsuite/ChangeLog:

	PR c++/66850
	* g++.dg/template/pr66850.C: New test.

From-SVN: r225801

gcc/cp/ChangeLog

@@ -1,3 +1,12 @@
+2015-07-14  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/66850
+	* pt.c (redeclare_class_template): Set the DECL_CONTEXTs of each
+	template template parm in the redeclaration.
+	(lookup_template_class_1): Peel off irrelevant template levels
+	from current_template_parms before augmenting the argument
+	list.
+
 2015-07-14  Andrea Azzarone  <azzaronea@gmail.com>
 
 	PR c++/65071

gcc/cp/pt.c

@@ -5302,6 +5302,14 @@ redeclare_class_template (tree type, tree parms)
 	/* Update the new parameters, too; they'll be used as the
 	   parameters for any members.  */
 	TREE_PURPOSE (TREE_VEC_ELT (parms, i)) = tmpl_default;
+
+      /* Give each template template parm in this redeclaration a
+	 DECL_CONTEXT of the template for which they are a parameter.  */
+      if (TREE_CODE (parm) == TEMPLATE_DECL)
+	{
+	  gcc_assert (DECL_CONTEXT (parm) == NULL_TREE);
+	  DECL_CONTEXT (parm) = tmpl;
+	}
     }
 
     return true;
@@ -7754,9 +7762,20 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
       if (outer)
 	outer = TI_ARGS (get_template_info (DECL_TEMPLATE_RESULT (outer)));
       else if (current_template_parms)
-	/* This is an argument of the current template, so we haven't set
+	{
-	   DECL_CONTEXT yet.  */
+	  /* This is an argument of the current template, so we haven't set
-	outer = current_template_args ();
+	     DECL_CONTEXT yet.  */
+	  tree relevant_template_parms;
+
+	  /* Parameter levels that are greater than the level of the given
+	     template template parm are irrelevant.  */
+	  relevant_template_parms = current_template_parms;
+	  while (TMPL_PARMS_DEPTH (relevant_template_parms)
+		 != TEMPLATE_TYPE_LEVEL (TREE_TYPE (templ)))
+	    relevant_template_parms = TREE_CHAIN (relevant_template_parms);
+
+	  outer = template_parms_to_args (relevant_template_parms);
+	}
 
       if (outer)
 	arglist = add_to_template_args (outer, arglist);

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2015-07-14  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/66850
+	* g++.dg/template/pr66850.C: New test.
+
 2015-07-14  Sandra Loosemore  <sandra@codesourcery.com>
 	    Cesar Philippidis  <cesar@codesourcery.com>
 	    Chung-Lin Tang  <cltang@codesourcery.com>

gcc/testsuite/g++.dg/template/pr66850.C

@@ -0,0 +1,44 @@
+// PR c++/66850
+// Each namespace contains an otherwise standalone test case, none of which
+// should cause an ICE.
+
+namespace X {
+  template <template <typename U, U> class> struct Sort;
+
+  template <template <typename U, U> class Comparator>
+  struct Sort
+  {
+    template <int I>
+    struct less_than
+    {
+      Comparator<int, I> a;
+    };
+  };
+}
+
+namespace Y {
+  template <typename C, C> struct integral_constant {};
+
+  template <typename T, template <typename U, U> class> struct Sort;
+
+  template <template <typename U, U> class Comparator>
+  struct Sort<int, Comparator>
+  {
+      template <int I> struct less_than:
+          integral_constant<bool, Comparator<int, I>::value> {};
+  };
+}
+
+namespace Z {
+  template <typename T, template <typename U, U> class> struct Sort;
+
+  template <template <typename U, U> class Comparator>
+  struct Sort<int, Comparator>
+  {
+    template <int I>
+    struct less_than
+    {
+      Comparator<int, I> a;
+    };
+  };
+}