Handle operators correctly.

pkg/front_end/test/fasta/operators.dart

+// Copyright (c) 2017, 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.
+
+class Operators {
+  operator +(other) => null;
+  operator &(other) => null;
+  operator ~() => null;
+  operator |(other) => null;
+  operator ^(other) => null;
+  operator /(other) => null;
+  operator ==(other) => null;
+  operator >(other) => null;
+  operator >=(other) => null;
+  operator [](index) => null;
+  void operator []=(index, value) {}
+  operator <<(other) => null;
+  operator <(other) => null;
+  operator <=(other) => null;
+  operator *(other) => null;
+  operator %(other) => null;
+  operator >>(other) => null;
+  operator -(other) => null;
+  operator ~/(other) => null;
+  operator -() => null;
+}
+
+main(arguments) {
+  var a = new Operators();
+  var b = new Operators();
+  a + b;
+  a & b;
+  ~a;
+  a | b;
+  a ^ b;
+  a / b;
+  a == b;
+  a > b;
+  a >= b;
+  a[0];
+  a[0] = b;
+  a << b;
+  a < b;
+  a <= b;
+  a * b;
+  a % b;
+  a >> b;
+  a - b;
+  a ~/ b;
+  -a;
+}