Emit read-modify-write of fields as assignment op.

tests/compiler/dart2js/field_update_test.dart

+// Copyright (c) 2014, 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.
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+import 'compiler_helper.dart';
+
+// Test for emitting JavaScript pre- and post-increment and assignment ops.
+
+const String TEST_1 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a + 1; return r; }  // this.a++
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+const String TEST_2 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a + 1; return a; }  // ++this.a
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+const String TEST_3 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a - 1; return r; }  // this.a--
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+const String TEST_4 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a - 1; return a; }  // --this.a
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+const String TEST_5 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a - 2; return a; }  // this.a -= 2
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+const String TEST_6 = """
+class A {
+  var a = 42;
+  int foo() { var r = a; a = a * 2; return a; }  // this.a *= 2
+}
+
+void main() {
+  var a = new A();
+  print(a.foo());
+}
+""";
+
+
+main() {
+  test(String code, Function f) {
+    asyncTest(() => compileAll(code, disableInlining: true).then((generated) {
+      Expect.isTrue(f(generated));
+    }));
+  }
+
+  test(TEST_1, (generated) => generated.contains(r'return this.a++;'));
+  test(TEST_2, (generated) => generated.contains(r'return ++this.a;'));
+  test(TEST_3, (generated) => generated.contains(r'return this.a--;'));
+  test(TEST_4, (generated) => generated.contains(r'return --this.a;'));
+  test(TEST_5, (generated) => generated.contains(r' this.a -= 2;'));
+  test(TEST_6, (generated) => generated.contains(r' this.a *= 2;'));
+}