dart2dart: Test cases for better code coverage in dart_tree rewritings.

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);
-}