Reapply "Convert HashSet, LinkedHashSet to factory methods and custom implementations."

tests/corelib/map_test.dart

 // Copyright (c) 2011, 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.
 
 library map_test;
 import "package:expect/expect.dart";
 import 'dart:collection';
 
 void main() {
   test(new HashMap());
@@ skipping 438 matching lines @@
     if (key.isNaN) count++;
   });
   Expect.equals(2, count);
 
   map.clear();
   Expect.isTrue(map.isEmpty);
 }
 
 void testLength(int length, Map map) {
   Expect.equals(length, map.length);
-  (length == 0 ? Expect.isTrue : Expect.isFalse)(map.isEmpty);
-  (length != 0 ? Expect.isTrue : Expect.isFalse)(map.isNotEmpty);
+  Expect.equals(length, map.keys.length);
+  Expect.equals(length, map.values.length);
+  // Check being-empty.
+  var ifEmpty = (length == 0) ? Expect.isTrue : Expect.isFalse;
+  var ifNotEmpty = (length != 0) ? Expect.isTrue : Expect.isFalse;
+  ifEmpty(map.isEmpty);
+  ifNotEmpty(map.isNotEmpty);
+  ifEmpty(map.keys.isEmpty);
+  ifNotEmpty(map.keys.isNotEmpty);
+  ifEmpty(map.values.isEmpty);
+  ifNotEmpty(map.values.isNotEmpty);
+  // Test key/value iterators match their isEmpty/isNotEmpty.
+  ifNotEmpty(map.keys.iterator.moveNext());
+  ifNotEmpty(map.values.iterator.moveNext());
+  if (length == 0) {
+    for (var k in map.keys) Expect.fail("contains key when iterating: $k");
+    for (var v in map.values) Expect.fail("contains values when iterating: $v");
+  }
 }
 
 
 testIdentityMap(Map map) {
   Expect.isTrue(map.isEmpty);
 
   var nan = double.NAN;
   // TODO(11551): Remove guard when dart2js makes identical(NaN, NaN) true.
   if (identical(nan, nan)) {
     map[nan] = 42;
@@ skipping 219 matching lines @@
   map[0] = 0;
   map[1] = 1;
   map[2] = 2;
   Expect.isFalse(map.containsKey("not an int"));
   Expect.isFalse(map.containsKey(1.5));
   Expect.isNull(map.remove("not an int"));
   Expect.isNull(map.remove(1.5));
   Expect.isNull(map["not an int"]);
   Expect.isNull(map[1.5]);
 }