Operators.

frog/tests/leg_only/src/CompoundOperatorIndexTest.dart

+// Copyright (c) 2012, 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 A {
+  List<int> list;
+  A(int a, int b) : list = <int>[a, b];
+  operator [](index) => list[index];
+  operator []=(index, value) => list[index] = value;
+}
+
+class B {
+  int value;
+  List trace;
+  B(this.trace) : value = 100;
+  operator [](index) {
+    trace.add(-3);
+    trace.add(index);
+    trace.add(this.value);
+    this.value = this.value + 1;
+    return this;
+  }
+
+  operator []=(index, value) {
+    trace.add(-5);
+    trace.add(index);
+    trace.add(value.value);
+    this.value = this.value + 1;
+  }
+
+  operator +(int value) {
+    trace.add(-4);
+    trace.add(this.value);
+    trace.add(value);
+    this.value = this.value + 1;
+    return this;
+  }
+}
+
+B getB(trace) {
+  trace.add(-1);
+  return new B(trace);
+}
+int getIndex(trace) {
+  trace.add(-2);
+  return 42;
+}
+
+main() {
+  A a = new A(1, 2);
+  Expect.equals(1, a[0]);
+  Expect.equals(2, a[1]);
+
+  Expect.equals(1, a[0]++);
+  Expect.equals(2, a[0]);
+
+  Expect.equals(2, a[0]--);
+  Expect.equals(1, a[0]);
+
+  Expect.equals(0, --a[0]);
+  Expect.equals(0, a[0]);
+
+  Expect.equals(1, ++a[0]);
+  Expect.equals(1, a[0]);
+
+  a[0] += 2;
+  Expect.equals(3, a[0]);
+
+  List trace = new List();
+  getB(trace)[getIndex(trace)] += 37;
+
+  Expect.listEquals([-1, -2, -3, 42, 100, -4, 101, 37, -5, 42, 102], trace);
+}