re PR c++/36797 (ICE mangling __is_empty)

	PR c++/36797
	* mangle.c (write_expression): Improve diagnostic for TRAIT_EXPR.

From-SVN: r184874

gcc/cp/ChangeLog

 2012-03-03  Jason Merrill  <jason@redhat.com>
 
+	PR c++/36797
+	* mangle.c (write_expression): Improve diagnostic for TRAIT_EXPR.
+
 	* class.c (add_method): Always build an OVERLOAD for using-decls.
 	* search.c (lookup_member): Handle getting an OVERLOAD for a
 	single function.

gcc/cp/mangle.c

@@ -2808,7 +2808,17 @@ write_expression (tree expr)
 
       if (name == NULL)
 	{
-	  sorry ("mangling %C", code);
+	  switch (code)
+	    {
+	    case TRAIT_EXPR:
+	      error ("use of built-in trait %qE in function signature; "
+		     "use library traits instead", expr);
+	      break;
+
+	    default:
+	      sorry ("mangling %C", code);
+	      break;
+	    }
 	  return;
 	}
       else

gcc/testsuite/ChangeLog

+2012-03-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/36797
+	* g++.dg/ext/is_empty2.C: New.
+
 2012-03-03  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/48820

gcc/testsuite/g++.dg/ext/is_empty2.C

+// PR c++/36797
+
+template <int> struct A { };
+
+template <class T>
+int foo (A<__is_empty (T)>* = 0); // { dg-error "built-in trait" }
+
+int main ()
+{
+    foo<int>();
+}