re PR c++/9127 (Confusing diagnostic on specialization not introduced by "template<>")

PR c++/9127
	* cp-tree.h (at_namespace_scope_p): New function.
	* parser.c (cp_parser_class_head): Handle invalid explicit
	specializations.
	* search.c (at_namespace_scope_p): New function.

	PR c++/9127
	* g++.dg/template/error6.C: New test.

From-SVN: r74274

gcc/cp/ChangeLog

@@ -5,6 +5,12 @@
 
 2003-12-03  Mark Mitchell  <mark@codesourcery.com>
 
+	PR c++/9127
+	* cp-tree.h (at_namespace_scope_p): New function.
+	* parser.c (cp_parser_class_head): Handle invalid explicit
+	specializations.
+	* search.c (at_namespace_scope_p): New function.
+
 	PR c++/13179
 	* semantics.c (finish_handler_parms): Do not call eh_type_info for
 	types used in templates.

gcc/cp/cp-tree.h

@@ -3966,6 +3966,7 @@ extern void reinit_search_statistics		(void);
 extern tree current_scope			(void);
 extern int at_function_scope_p                  (void);
 extern bool at_class_scope_p                    (void);
+extern bool at_namespace_scope_p                (void);
 extern tree context_for_name_lookup		(tree);
 extern tree lookup_conversions			(tree);
 extern tree binfo_for_vtable			(tree);

gcc/cp/parser.c

@@ -11584,6 +11584,7 @@ cp_parser_class_head (cp_parser* parser,
   bool template_id_p = false;
   bool qualified_p = false;
   bool invalid_nested_name_p = false;
+  bool invalid_explicit_specialization_p = false;
   unsigned num_templates;
 
   /* Assume no nested-name-specifier will be present.  */
@@ -11732,12 +11733,31 @@ cp_parser_class_head (cp_parser* parser,
   else if (invalid_nested_name_p)
     cp_parser_error (parser,
 		     "qualified name does not name a class");
+  /* An explicit-specialization must be preceded by "template <>".  If
+     it is not, try to recover gracefully.  */
+  if (at_namespace_scope_p () 
+      && parser->num_template_parameter_lists == 0
+      && num_templates == 1)
+    {
+      error ("an explicit specialization must be preceded by 'template <>'");
+      invalid_explicit_specialization_p = true;
+      /* Take the same action that would have been taken by
+	 cp_parser_explicit_specialization.  */
+      ++parser->num_template_parameter_lists;
+      begin_specialization ();
+    }
+  /* There must be no "return" statements between this point and the
+     end of this function; set "type "to the correct return value and
+     use "goto done;" to return.  */
   /* Make sure that the right number of template parameters were
      present.  */
   if (!cp_parser_check_template_parameters (parser, num_templates))
-    /* If something went wrong, there is no point in even trying to
-       process the class-definition.  */
-    return NULL_TREE;
+    {
+      /* If something went wrong, there is no point in even trying to
+	 process the class-definition.  */
+      type = NULL_TREE;
+      goto done;
+    }
 
   /* Look up the type.  */
   if (template_id_p)
@@ -11789,7 +11809,8 @@ cp_parser_class_head (cp_parser* parser,
 	{
 	  error ("declaration of `%D' in `%D' which does not "
 		 "enclose `%D'", type, scope, nested_name_specifier);
-	  return NULL_TREE;
+	  type = NULL_TREE;
+	  goto done;
 	}
       /* [dcl.meaning]
 
@@ -11848,6 +11869,12 @@ cp_parser_class_head (cp_parser* parser,
   if (nested_name_specifier)
     pop_scope (nested_name_specifier);
 
+ done:
+  if (invalid_explicit_specialization_p)
+    {
+      end_specialization ();
+      --parser->num_template_parameter_lists;
+    }
   return type;
 }
 

gcc/cp/search.c

@@ -580,6 +580,16 @@ at_class_scope_p (void)
   return cs && TYPE_P (cs);
 }
 
+/* Returns true if the innermost active scope is a namespace scope.  */
+
+bool
+at_namespace_scope_p (void)
+{
+  /* We are in a namespace scope if we are not it a class scope or a
+     function scope.  */
+  return !current_scope();
+}
+
 /* Return the scope of DECL, as appropriate when doing name-lookup.  */
 
 tree

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2003-12-03  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/9127
+	* g++.dg/template/error6.C: New test.
+
 2003-12-03  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.dg/20031202-1.c: New test.

gcc/testsuite/g++.dg/template/error6.C

@@ -0,0 +1,13 @@
+template<int n>
+struct tento {
+  enum {value = 10*tento<n-1>::value};
+};
+
+struct tento<0> { // { dg-error "" }
+   enum {value=1};
+};
+
+int main() {
+  if (tento<4>::value != 10000) return -1;
+}
+