Re: [C++ Patch] PR 53856

[Paolo Carlini <paolo.carlini@oracle.com>]

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Hi,

On 10/05/2015 07:10 PM, Jason Merrill wrote:
> On 10/05/2015 12:50 PM, Paolo Carlini wrote:
>> +  else if (!current_class_type || CLASSTYPE_IS_TEMPLATE 
>> (current_class_type))
>> +    msg = G_("default argument for template parameter for class 
>> enclosing %qD");
>
> Why would this be right when !current_class_type?
Yes, it doesn't make much sense, but at least it's conservatively 
correct ;) I'm finishing regtesting the below, everything seems fine so 
far. Ok if it passes?

Thanks,
Paolo.

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Index: cp/pt.c
===================================================================
--- cp/pt.c	(revision 228467)
+++ cp/pt.c	(working copy)
@@ -4940,8 +4940,15 @@ check_default_tmpl_args (tree decl, tree parms, bo
   else if (is_partial)
     msg = G_("default template arguments may not be used in "
 	     "partial specializations");
+  else if (current_class_type && CLASSTYPE_IS_TEMPLATE (current_class_type))
+    msg = G_("default argument for template parameter for class enclosing %qD");
   else
-    msg = G_("default argument for template parameter for class enclosing %qD");
+    /* Per [temp.param]/9, "A default template-argument shall not be
+       specified in the template-parameter-lists of the definition of
+       a member of a class template that appears outside of the member's
+       class.", thus if we aren't handling a member of a class template
+       there is no need to examine the parameters.  */
+    return true;
 
   if (current_class_type && TYPE_BEING_DEFINED (current_class_type))
     /* If we're inside a class definition, there's no need to
Index: testsuite/g++.dg/template/defarg19.C
===================================================================
--- testsuite/g++.dg/template/defarg19.C	(revision 0)
+++ testsuite/g++.dg/template/defarg19.C	(working copy)
@@ -0,0 +1,15 @@
+// PR c++/53856
+
+template<typename T>
+struct A
+{
+  struct B;
+};
+
+template<typename T = int>
+struct A<T>::B  // { dg-error "default argument" }
+{
+  int i;
+};
+
+A<int>::B b = { };
Index: testsuite/g++.dg/template/defarg20.C
===================================================================
--- testsuite/g++.dg/template/defarg20.C	(revision 0)
+++ testsuite/g++.dg/template/defarg20.C	(working copy)
@@ -0,0 +1,15 @@
+// PR c++/53856
+
+struct A
+{
+  template<typename T>
+  struct B;
+};
+
+template<typename T = int>
+struct A::B
+{
+  int i;
+};
+
+A::B<int> b = { };