C++ PATCH for c++/40746

[Jason Merrill <jason at redhat dot com>]

While working on fixing the standard wording for inline namespaces, I 
noticed what looked like an error in the logic for handling 
using-directives in qualified lookup.  Actually, it seems that Alexandre 
noticed it too, as indicated by his ??? comment.  So I whipped up a 
testcase and fixed it.

Tested x86_64-pc-linux-gnu, applied to trunk.

2009-07-14  Jason Merrill  <jason@redhat.com>

	PR c++/40746
	* name-lookup.c (qualified_lookup_using_namespace): Don't stop
	looking in used namespaces just because we found something on
	another branch.

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index c1032e3..7a8016f 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -3929,6 +3929,7 @@ qualified_lookup_using_namespace (tree name, tree scope,
   /* ... and a list of namespace yet to see.  */
   tree todo = NULL_TREE;
   tree todo_maybe = NULL_TREE;
+  tree *todo_weak = &todo_maybe;
   tree usings;
   timevar_push (TV_NAME_LOOKUP);
   /* Look through namespace aliases.  */
@@ -3942,9 +3943,7 @@ qualified_lookup_using_namespace (tree name, tree scope,
 	ambiguous_decl (result, binding, flags);
 
       /* Consider strong using directives always, and non-strong ones
-	 if we haven't found a binding yet.  ??? Shouldn't we consider
-	 non-strong ones if the initial RESULT is non-NULL, but the
-	 binding in the given namespace is?  */
+	 if we haven't found a binding yet.  */
       for (usings = DECL_NAMESPACE_USING (scope); usings;
 	   usings = TREE_CHAIN (usings))
 	/* If this was a real directive, and we have not seen it.  */
@@ -3959,12 +3958,12 @@ qualified_lookup_using_namespace (tree name, tree scope,
 		&& !purpose_member (TREE_PURPOSE (usings), seen)
 		&& !purpose_member (TREE_PURPOSE (usings), todo))
 	      todo = tree_cons (TREE_PURPOSE (usings), NULL_TREE, todo);
-	    else if ((!result->value && !result->type)
+	    else if (!binding
 		     && !purpose_member (TREE_PURPOSE (usings), seen)
 		     && !purpose_member (TREE_PURPOSE (usings), todo)
 		     && !purpose_member (TREE_PURPOSE (usings), todo_maybe))
-	      todo_maybe = tree_cons (TREE_PURPOSE (usings), NULL_TREE,
-				      todo_maybe);
+	      *todo_weak = tree_cons (TREE_PURPOSE (usings), NULL_TREE,
+				      *todo_weak);
 	  }
       if (todo)
 	{
@@ -3977,6 +3976,7 @@ qualified_lookup_using_namespace (tree name, tree scope,
 	  scope = TREE_PURPOSE (todo_maybe);
 	  todo = TREE_CHAIN (todo_maybe);
 	  todo_maybe = NULL_TREE;
+	  todo_weak = &todo;
 	}
       else
 	scope = NULL_TREE; /* If there never was a todo list.  */
diff --git a/gcc/testsuite/g++.dg/lookup/using20.C b/gcc/testsuite/g++.dg/lookup/using20.C
new file mode 100644
index 0000000..dc1d293
--- /dev/null
+++ b/gcc/testsuite/g++.dg/lookup/using20.C
@@ -0,0 +1,18 @@
+// PR c++/40476
+
+namespace A
+{
+  int i;			// { dg-error "i" }
+}
+using namespace A;
+namespace B
+{
+  namespace B2
+  {
+    int i;			// { dg-error "i" }
+  }
+  using namespace B2;
+}
+using namespace B;
+
+int j = ::i;			// { dg-error "ambiguous" }