Implement cascaded calls.

frog/tests/leg_only/src/CascadeTest.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.
+
+// Test cascades.
+
+class A {
+  int x;
+  int y;
+  A(this.x, this.y);
+  A setX(int x) { this.x = x; return this; }

[ahe, 2012/04/16 08:55:23]

Would be nice with a single empty line between the various functions, accessors,
and constructors.

[Lasse Reichstein Nielsen, 2012/04/16 12:41:38]

Done.

+  void setY(int y) { this.y = y; }
+  Function swap() {
+    int tmp = x;
+    x = y;
+    y = tmp;
+    return this.swap;
+  }
+  void check(int x, int y) {
+    Expect.equals(x, this.x);
+    Expect.equals(y, this.y);
+  }
+  int operator[](var i) {
+    if (i == 0) return x;
+    if (i == 1) return y;
+    if (i == "swap") return this.swap;
+    return null;
+  }
+  int operator[]=(int i, int value) {
+    if (i == 0) {
+      x = value;
+    } else if (i == 1) {
+      y = value;
+    }
+  }
+}
+
+main() {
+  A a = new A(1, 2);
+  a..check(1, 2)
+   ..swap()..check(2, 1)
+   ..x = 4..y = 9..check(4, 9)
+   ..setX(10)..check(10, 9)
+   ..y = 5..check(10, 5)
+   ..swap()()()..check(5, 10)
+   ..[0] = 2..check(2, 10)
+   ..setX(10).setY(3)..check(10, 3)
+   ..setX(7)["swap"]()..check(3, 7)
+   ..["swap"]()()()..check(7, 3);

[ahe, 2012/04/16 08:55:23]

I think this test will pass if cascades are no-ops, so how about adding:

a.check(7, 3);

[Lasse Reichstein Nielsen, 2012/04/16 12:41:38]

Good point. Done.

+  a..(42);  /// 01: compile-time error

[ahe, 2012/04/16 08:55:23]

Additional suggestions for tests:

a..42; /// 02: compile-time error
a..""; /// 03: compile-time error

[Lasse Reichstein Nielsen, 2012/04/16 12:41:38]

Done.

+}