dart2dart: Use implicit 'this' when generating Dart code.

tests/language/rewrite_implicit_this_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";
+
+String toplevel = 'A';
+
+class Foo {
+    String x = 'x';
+
+    easy(z) {
+        return x + y + z;
+    }
+
+    // Shadow the 'y' field in various ways
+    shadow_y_parameter(y) {
+        return x + this.y + y;
+    }
+
+    shadow_y_local(z) {
+        var y = z;
+        return x + this.y + y;
+    }
+
+    shadow_y_capturedLocal(z) {
+        var y = z;
+        foo() {
+            return x + this.y + y;
+        }
+        return foo();
+    }
+
+    shadow_y_closureParam(z) {
+        foo(y) {
+            return x + this.y + y;
+        }
+        return foo(z);
+    }
+
+    shadow_y_localInsideClosure(z) {
+        foo() {
+            var y = z;
+            return x + this.y + y;
+        }
+        return foo();
+    }
+
+    // Shadow the 'x' field in various ways
+    shadow_x_parameter(x) {
+        return this.x + y + x;
+    }
+
+    shadow_x_local(z) {
+        var x = z;
+        return this.x + y + x;
+    }
+
+    shadow_x_capturedLocal(z) {
+        var x = z;
+        foo() {
+            return this.x + y + x;
+        }
+        return foo();
+    }
+
+    shadow_x_closureParam(z) {
+        foo(x) {
+            return this.x + y + x;
+        }
+        return foo(z);
+    }
+
+    shadow_x_localInsideClosure(z) {
+        foo() {
+            var x = z;
+            return this.x + y + x;
+        }
+        return foo();
+    }
+
+    shadow_x_toplevel() {
+        return x + this.y + toplevel + this.toplevel;
+    }
+    
+}
+
+class Sub extends Foo {
+    String y = 'y';
+    String toplevel = 'B';
+}
+
+main() {
+    Expect.equals('xyz', new Sub().easy('z'));
+    Expect.equals('xyz', new Sub().shadow_y_parameter('z'));
+    Expect.equals('xyz', new Sub().shadow_y_local('z'));
+    Expect.equals('xyz', new Sub().shadow_y_capturedLocal('z'));
+    Expect.equals('xyz', new Sub().shadow_y_closureParam('z'));
+    Expect.equals('xyz', new Sub().shadow_y_localInsideClosure('z'));
+    Expect.equals('xyz', new Sub().shadow_x_parameter('z'));
+    Expect.equals('xyz', new Sub().shadow_x_local('z'));
+    Expect.equals('xyz', new Sub().shadow_x_capturedLocal('z'));
+    Expect.equals('xyz', new Sub().shadow_x_closureParam('z'));
+    Expect.equals('xyz', new Sub().shadow_x_localInsideClosure('z'));
+
+    Expect.equals('xyAB', new Sub().shadow_x_toplevel());
+}