dart2dart: Logical operators and related rewrite rules in dart_tree.

tests/language/if_flatten1_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';
+
+var global;
+
+setGlobal(v) {
+  global = v;
+}
+
+check_true_true(x, y, v) {
+  if (x) {
+    if (y) {
+      setGlobal(v);
+    }
+  }
+}
+
+check_false_true(x, y, v) {
+  if (x) {
+
+  } else {
+    if (y) {
+      setGlobal(v);
+    }
+  }
+}
+
+check_true_false(x, y, v) {
+  if (x) {
+    if (y) {
+
+    } else {
+      setGlobal(v);
+    }
+  }
+}
+
+check_false_false(x, y, v) {
+  if (x) {
+
+  } else {
+    if (y) {
+
+    } else {
+      setGlobal(v);
+    }
+  }
+}
+
+
+main() {
+  check_true_true(true,  true,  4);
+  check_true_true(false, false, 1);
+  check_true_true(false, true,  2);
+  check_true_true(true,  false, 3);
+
+  Expect.equals(4, global);
+
+  check_true_false(false, false, 1);
+  check_true_false(false, true,  2);
+  check_true_false(true,  false, 3);
+  check_true_false(true,  true,  4);
+
+  Expect.equals(3, global);
+
+  check_false_true(false, false, 1);
+  check_false_true(false, true,  2);
+  check_false_true(true,  false, 3);
+  check_false_true(true,  true,  4);
+
+  Expect.equals(2, global);
+
+  check_false_false(false, false, 1);
+  check_false_false(false, true,  2);
+  check_false_false(true,  false, 3);
+  check_false_false(true,  true,  4);
+
+  Expect.equals(1, global);
+}