re PR c++/34751 (ICE with pointer to member and variadic templates)

2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>

	PR c++/34751
	* pt.c (coerce_template_parameter_pack): When substituting into
	the type of a non-type template parameter pack. use the
	deduced/substituted arguments.
	* parser.c (declarator_can_be_parameter_pack): A pointer-to-member
	can be a parameter pack with the ellipsis following it.  When we
	have an erroneous declaration, allow it to be a parameter pack.
	(cp_parser_template_parameter): Complain about default
	arguments on non-type template parameter packs, and parse them
	using the new cp_parser_default_argument.
	(cp_parser_parameter_declaration): Complain about parameter packs
	with default arguments. Move parsing of default arguments into a
	new function, cp_parser_default_argument.
	(cp_parser_default_argument): New; extracted from
	cp_parser_parameter_declaration.

2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>

	PR c++/34751
	* g++.dg/cpp0x/vt-34751.C: New.

From-SVN: r131548

gcc/cp/ChangeLog

 2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>
 
+	PR c++/34751
+	* pt.c (coerce_template_parameter_pack): When substituting into
+	the type of a non-type template parameter pack. use the
+	deduced/substituted arguments.
+	* parser.c (declarator_can_be_parameter_pack): A pointer-to-member
+	can be a parameter pack with the ellipsis following it.  When we
+	have an erroneous declaration, allow it to be a parameter pack.
+	(cp_parser_template_parameter): Complain about default
+	arguments on non-type template parameter packs, and parse them
+	using the new cp_parser_default_argument.
+	(cp_parser_parameter_declaration): Complain about parameter packs
+	with default arguments. Move parsing of default arguments into a
+	new function, cp_parser_default_argument.
+	(cp_parser_default_argument): New; extracted from
+	cp_parser_parameter_declaration.
+
+2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>
+
 	PR c++/34051
 	PR c++/34055
 	PR c++/34102

gcc/cp/parser.c

@@ -1071,12 +1071,13 @@ declarator_can_be_parameter_pack (cp_declarator *declarator)
       switch ((int)declarator->kind)
 	{
 	case cdk_id:
-	case cdk_error:
 	case cdk_array:
-	case cdk_ptrmem:
 	  found = true;
 	  break;
-	  
+
+	case cdk_error:
+	  return true;
+
 	default:
 	  declarator = declarator->declarator;
 	  break;
@@ -1734,6 +1735,8 @@ static cp_parameter_declarator *cp_parser_parameter_declaration_list
   (cp_parser *, bool *);
 static cp_parameter_declarator *cp_parser_parameter_declaration
   (cp_parser *, bool, bool *);
+static tree cp_parser_default_argument 
+  (cp_parser *, bool);
 static void cp_parser_function_body
   (cp_parser *);
 static tree cp_parser_initializer
@@ -9385,16 +9388,39 @@ cp_parser_template_parameter (cp_parser* parser, bool *is_non_type,
 
   /* If the next token is an ellipsis, and we don't already have it
      marked as a parameter pack, then we have a parameter pack (that
-     has no declarator); */
+     has no declarator).  */
   if (!*is_parameter_pack
       && cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS)
       && declarator_can_be_parameter_pack (parameter_declarator->declarator))
     {
-      /* Consume the `...'. */
+      /* Consume the `...'.  */
       cp_lexer_consume_token (parser->lexer);
       maybe_warn_variadic_templates ();
       
       *is_parameter_pack = true;
+
+      /* Parameter packs cannot have default arguments.  However, a
+	 user may try to do so, so we'll parse them and give an
+	 appropriate diagnostic here.  */
+      if (cp_lexer_next_token_is (parser->lexer, CPP_EQ))
+	{
+	  /* Consume the `='.  */
+	  cp_lexer_consume_token (parser->lexer);
+
+	  /* Find the name of the parameter pack.  */     
+	  cp_declarator *id_declarator = parameter_declarator->declarator;
+	  while (id_declarator && id_declarator->kind != cdk_id)
+	    id_declarator = id_declarator->declarator;
+	  
+	  if (id_declarator && id_declarator->kind == cdk_id)
+	    error ("template parameter pack %qD cannot have a default argument",
+		   id_declarator->u.id.unqualified_name);
+	  else
+	    error ("template parameter pack cannot have a default argument");
+
+          /* Parse the default argument, but throw away the result.  */
+          cp_parser_default_argument (parser, /*template_parm_p=*/true);
+	}
     }
 
   parm = grokdeclarator (parameter_declarator->declarator,
@@ -13540,7 +13566,6 @@ cp_parser_parameter_declaration (cp_parser *parser,
   /* If the next token is `=', then process a default argument.  */
   if (cp_lexer_next_token_is (parser->lexer, CPP_EQ))
     {
-      bool saved_greater_than_is_operator_p;
       /* Consume the `='.  */
       cp_lexer_consume_token (parser->lexer);
 
@@ -13646,39 +13671,9 @@ cp_parser_parameter_declaration (cp_parser *parser,
       /* Outside of a class definition, we can just parse the
 	 assignment-expression.  */
       else
-	{
-	  bool saved_local_variables_forbidden_p;
-
-	  /* Make sure that PARSER->GREATER_THAN_IS_OPERATOR_P is
-	     set correctly.  */
-	  saved_greater_than_is_operator_p
-	    = parser->greater_than_is_operator_p;
-	  parser->greater_than_is_operator_p = greater_than_is_operator_p;
-	  /* Local variable names (and the `this' keyword) may not
-	     appear in a default argument.  */
-	  saved_local_variables_forbidden_p
-	    = parser->local_variables_forbidden_p;
-	  parser->local_variables_forbidden_p = true;
-	  /* The default argument expression may cause implicitly
-	     defined member functions to be synthesized, which will
-	     result in garbage collection.  We must treat this
-	     situation as if we were within the body of function so as
-	     to avoid collecting live data on the stack.  */
-	  ++function_depth;
-	  /* Parse the assignment-expression.  */
-	  if (template_parm_p)
-	    push_deferring_access_checks (dk_no_deferred);
-	  default_argument
-	    = cp_parser_assignment_expression (parser, /*cast_p=*/false);
-	  if (template_parm_p)
-	    pop_deferring_access_checks ();
-	  /* Restore saved state.  */
-	  --function_depth;
-	  parser->greater_than_is_operator_p
-	    = saved_greater_than_is_operator_p;
-	  parser->local_variables_forbidden_p
-	    = saved_local_variables_forbidden_p;
-	}
+        default_argument 
+          = cp_parser_default_argument (parser, template_parm_p);
+
       if (!parser->default_arg_ok_p)
 	{
 	  if (!flag_pedantic_errors)
@@ -13689,6 +13684,26 @@ cp_parser_parameter_declaration (cp_parser *parser,
 	      default_argument = NULL_TREE;
 	    }
 	}
+      else if ((declarator && declarator->parameter_pack_p)
+	       || (decl_specifiers.type
+		   && PACK_EXPANSION_P (decl_specifiers.type)))
+	{
+	  const char* kind = template_parm_p? "template " : "";
+	  
+	  /* Find the name of the parameter pack.  */     
+	  cp_declarator *id_declarator = declarator;
+	  while (id_declarator && id_declarator->kind != cdk_id)
+	    id_declarator = id_declarator->declarator;
+	  
+	  if (id_declarator && id_declarator->kind == cdk_id)
+	    error ("%sparameter pack %qD cannot have a default argument",
+		   kind, id_declarator->u.id.unqualified_name);
+	  else
+	    error ("%sparameter pack cannot have a default argument",
+		   kind);
+	  
+	  default_argument = NULL_TREE;
+	}
     }
   else
     default_argument = NULL_TREE;
@@ -13698,6 +13713,46 @@ cp_parser_parameter_declaration (cp_parser *parser,
 				    default_argument);
 }
 
+/* Parse a default argument and return it.
+
+   TEMPLATE_PARM_P is true if this is a default argument for a
+   non-type template parameter.  */
+static tree
+cp_parser_default_argument (cp_parser *parser, bool template_parm_p)
+{
+  tree default_argument = NULL_TREE;
+  bool saved_greater_than_is_operator_p;
+  bool saved_local_variables_forbidden_p;
+
+  /* Make sure that PARSER->GREATER_THAN_IS_OPERATOR_P is
+     set correctly.  */
+  saved_greater_than_is_operator_p = parser->greater_than_is_operator_p;
+  parser->greater_than_is_operator_p = !template_parm_p;
+  /* Local variable names (and the `this' keyword) may not
+     appear in a default argument.  */
+  saved_local_variables_forbidden_p = parser->local_variables_forbidden_p;
+  parser->local_variables_forbidden_p = true;
+  /* The default argument expression may cause implicitly
+     defined member functions to be synthesized, which will
+     result in garbage collection.  We must treat this
+     situation as if we were within the body of function so as
+     to avoid collecting live data on the stack.  */
+  ++function_depth;
+  /* Parse the assignment-expression.  */
+  if (template_parm_p)
+    push_deferring_access_checks (dk_no_deferred);
+  default_argument
+    = cp_parser_assignment_expression (parser, /*cast_p=*/false);
+  if (template_parm_p)
+    pop_deferring_access_checks ();
+  /* Restore saved state.  */
+  --function_depth;
+  parser->greater_than_is_operator_p = saved_greater_than_is_operator_p;
+  parser->local_variables_forbidden_p = saved_local_variables_forbidden_p;
+
+  return default_argument;
+}
+
 /* Parse a function-body.
 
    function-body:

gcc/cp/pt.c

@@ -5138,7 +5138,7 @@ coerce_template_parameter_pack (tree parms,
     {
       argument_pack = make_node (NONTYPE_ARGUMENT_PACK);
       TREE_TYPE (argument_pack) 
-        = tsubst (TREE_TYPE (TREE_VALUE (parm)), args, complain, in_decl);
+        = tsubst (TREE_TYPE (TREE_VALUE (parm)), new_args, complain, in_decl);
       TREE_CONSTANT (argument_pack) = 1;
     }
 

gcc/testsuite/ChangeLog

 2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>
 
+	PR c++/34751
+	* g++.dg/cpp0x/vt-34751.C: New.
+
+2008-01-15  Douglas Gregor  <doug.gregor@gmail.com>
+
 	PR c++/34051
 	PR c++/34055
 	PR c++/34102

gcc/testsuite/g++.dg/cpp0x/vt-34751.C

+// { dg-options "-std=c++0x" }
+// PR c++/34751
+struct A {};
+
+template<typename... Args = int>  // { dg-error "cannot have a default" }
+void f(Args... args = 0); // { dg-error "cannot have a default argument" }
+
+template<typename... Args> 
+void g(Args... = 0); // { dg-error "cannot have a default argument" }
+
+
+template<int, typename T = A, int T::*...p = 0 > struct B {}; // { dg-error "cannot have a default argument|no default argument" }
+
+B<0> b;
+
+template<int, typename T = A, int T::*... = 0 > struct C {}; // { dg-error "cannot have a default argument|no default argument" }
+
+C<0> c;
+