frog: detect when getter/setter has incorrect number of arguments.

tests/language/src/SetterDeclarationNegativeTest.dart

Index: tests/language/src/SetterDeclarationNegativeTest.dart
diff --git a/tests/language/src/SetterDeclarationNegativeTest.dart b/tests/language/src/SetterDeclarationNegativeTest.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f1389d180dcec77c914365affae3102b79b3cd57
--- /dev/null
+++ b/tests/language/src/SetterDeclarationNegativeTest.dart
@@ -0,0 +1,13 @@
+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// Test that a setter has a single argument
+
+// too many arguments
+set m(var value, var extra) { }
+
+main() {
+  m = 1;
+}
+