c++: using overloaded with local decl [PR92918]

The problem here was that the lookup for 'impl' when parsing the template
only found the using-declaration, not the member function declaration.

This happened because when trying to add the member function declaration,
push_class_level_binding_1 saw that the current binding was a USING_DECL and
the new value is an overload, and decided to just return success.

That 'return true' dates back to r69921.  In
https://gcc.gnu.org/pipermail/gcc-patches/2003-July/110632.html Nathan
mentions that we only push dependent USING_DECLs, which is no longer the
case; now that we retain more USING_DECLs, handling this case like the other
overloaded function cases seems like the obvious solution.

gcc/cp/ChangeLog:

	PR c++/92918
	* name-lookup.c (push_class_level_binding_1): Do overload a new
	function with a previous using-declaration.

gcc/testsuite/ChangeLog:

	PR c++/92918
	* g++.dg/lookup/using66.C: New test.

gcc/cp/name-lookup.c

@@ -5520,7 +5520,7 @@ push_class_level_binding_1 (tree name, tree x)
 	old_decl = bval;
       else if (TREE_CODE (bval) == USING_DECL
 	       && OVL_P (target_decl))
-	return true;
+	old_decl = bval;
       else if (OVL_P (target_decl)
 	       && OVL_P (target_bval))
 	old_decl = bval;

gcc/testsuite/g++.dg/lookup/using66.C

@@ -0,0 +1,23 @@
+// PR c++/92918
+// { dg-do compile { target c++11 } }
+
+struct Base03
+{
+    static void impl();
+};
+
+struct Problem : Base03
+{
+    using Base03::impl;
+    static int impl(char const *);
+
+    template <typename T>
+    auto f(const T &t) const
+    -> decltype(impl(t))
+    {
+        return impl(t);
+    }
+};
+
+Problem t;
+int i = t.f("42");