re PR c++/78701 (ICE: unexpected expression N of kind template_parm_index)

	PR c++/78701
	* pt.c (type_unification_real): Check tsubst arg doesn't have
	remaining template parms before converting it.

	PR c++/78701
	* g++.dg/cpp0x/pr78701.C: New.

From-SVN: r243657

gcc/cp/ChangeLog

 2016-12-14  Nathan Sidwell  <nathan@acm.org>
 
+	PR c++/78701
+	* pt.c (type_unification_real): Check tsubst arg doesn't have
+	remaining template parms before converting it.
+
 	PR c++/69481
 	* cp-tree.h (TYPE_TEMPLATE_INFO_MAYBE_ALIAS): Always use
 	TYPE_ALIAS_TEMPLATE_INFO for aliases.

gcc/cp/pt.c

@@ -18991,14 +18991,19 @@ type_unification_real (tree tparms,
 	  if (DECL_P (parm))
 	    input_location = DECL_SOURCE_LOCATION (parm);
 	  arg = tsubst_template_arg (arg, full_targs, complain, NULL_TREE);
-	  arg = convert_template_argument (parm, arg, full_targs, complain,
-					   i, NULL_TREE);
+	  if (!uses_template_parms (arg))
+	    arg = convert_template_argument (parm, arg, full_targs, complain,
+					     i, NULL_TREE);
+	  else if (saw_undeduced < 2)
+	    arg = NULL_TREE;
+	  else
+	    arg = error_mark_node;
 	  input_location = save_loc;
 	  *checks = get_deferred_access_checks ();
 	  pop_deferring_access_checks ();
 	  if (arg == error_mark_node)
 	    return 1;
-	  else
+	  else if (arg)
 	    {
 	      TREE_VEC_ELT (targs, i) = arg;
 	      /* The position of the first default template argument,
@@ -19006,7 +19011,6 @@ type_unification_real (tree tparms,
 		 Record that.  */
 	      if (!NON_DEFAULT_TEMPLATE_ARGS_COUNT (targs))
 		SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (targs, i);
-	      continue;
 	    }
 	}
 

gcc/testsuite/ChangeLog

+2016-12-14  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/78701
+	* g++.dg/cpp0x/pr78701.C: New.
+
 2016-12-14  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	* gcc/testsuite/gcc.target/powerpc/vec-extract.h: If DO_TRACE is

gcc/testsuite/g++.dg/cpp0x/pr78701.C

+// PR c++/58707
+// { dg-do compile { target c++11 } }
+
+// ICE during deduction of default parms
+
+template <class T, T N = T(), bool B = N>
+  void f(T x) {}
+
+template void f<int> (int);