re PR c++/6492 (New boost regression (friends))

	PR c++/6492
	* pt.c (tsubst_friend_class): If the friend has an explicit scope,
	enter that scope before name lookup.

From-SVN: r52951

gcc/cp/pt.c

@@ -4831,12 +4831,19 @@ tsubst_friend_class (friend_tmpl, args)
 {
   tree friend_type;
   tree tmpl;
+  tree context;
 
-  /* First, we look for a class template.  */
-  if (DECL_CONTEXT (friend_tmpl))
-    tmpl = friend_tmpl;
-  else
+  context = DECL_CONTEXT (friend_tmpl);
+
+  if (context)
     {
+      if (TREE_CODE (context) == NAMESPACE_DECL)
+	push_nested_namespace (context);
+      else
+	push_nested_class (context, 2);
+    }
+
+  /* First, we look for a class template.  */
   tmpl = lookup_name (DECL_NAME (friend_tmpl), /*prefer_type=*/0); 
 
   /* But, if we don't find one, it might be because we're in a
@@ -4855,7 +4862,6 @@ tsubst_friend_class (friend_tmpl, args)
       tmpl = lookup_name (DECL_NAME (friend_tmpl), /*prefer_type=*/1);
       tmpl = maybe_get_template_decl_from_type_decl (tmpl);
     }
-    }
 
   if (tmpl && DECL_CLASS_TEMPLATE_P (tmpl))
     {
@@ -4865,12 +4871,15 @@ tsubst_friend_class (friend_tmpl, args)
 	 of course.  We only need the innermost template parameters
 	 because that is all that redeclare_class_template will look
 	 at.  */
-      tree parms 
-	= tsubst_template_parms (DECL_TEMPLATE_PARMS (friend_tmpl),
+      if (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (friend_tmpl))
+	  > TMPL_ARGS_DEPTH (args))
+	{
+	  tree parms;
+	  parms = tsubst_template_parms (DECL_TEMPLATE_PARMS (friend_tmpl),
 					 args, tf_error | tf_warning);
-      if (!parms)
-        return error_mark_node;
 	  redeclare_class_template (TREE_TYPE (tmpl), parms);
+	}
+
       friend_type = TREE_TYPE (tmpl);
     }
   else
@@ -4892,6 +4901,14 @@ tsubst_friend_class (friend_tmpl, args)
       friend_type = TREE_TYPE (pushdecl_top_level (tmpl));
     }
 
+  if (context) 
+    {
+      if (TREE_CODE (context) == NAMESPACE_DECL)
+	pop_nested_namespace (context);
+      else
+	pop_nested_class ();
+    }
+
   return friend_type;
 }