Add Symbol class.

dart/tests/corelib/symbol_test.dart

Index: dart/tests/corelib/symbol_test.dart
diff --git a/dart/tests/corelib/symbol_test.dart b/dart/tests/corelib/symbol_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..53387a2a465d2ec1bbf66f311897e7592f35380b
--- /dev/null
+++ b/dart/tests/corelib/symbol_test.dart
@@ -0,0 +1,59 @@
+// Copyright (c) 2013, 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.
+
+notString() => const Symbol(0);
+
+notIdentifier() => const Symbol('0');
+
+privateIdentifier() => const Symbol('_');
+
+main() {
+  var x;
+  print(x = const Symbol('fisk'));

[kasperl, 2013/04/11 10:48:58]

Maybe turn x into a list of symbols and check more legal identifiers with $, _,
digits in them?

+
+  try {
+    print(notString()); /// 01: compile-time error
+  } on ArgumentError {
+    print('Caught ArgumentError');
+  } on TypeError {
+    print('Caught TypeError');
+  }
+
+  try {
+    print(notIdentifier()); /// 02: compile-time error
+  } on ArgumentError catch (e) {
+    print('Caught $e');
+  }
+
+  try {
+    print(privateIdentifier()); /// 03: compile-time error
+  } on ArgumentError catch (e) {
+    print('Caught $e');
+  }
+
+  try {
+    print(new Symbol(0));
+    throw 'Expected an ArgumentError or a TypeError';
+  } on ArgumentError {
+    print('Caught ArgumentError');
+  } on TypeError {
+    print('Caught TypeError');
+  }
+
+  try {
+    print(new Symbol('0'));
+    throw 'Expected an ArgumentError';
+  } on ArgumentError catch (e) {
+    print('Caught $e');
+  }
+
+  try {
+    print(new Symbol('_'));
+    throw 'Expected an ArgumentError';
+  } on ArgumentError catch (e) {
+    print('Caught $e');
+  }
+
+  print(identical(const Symbol('fisk'), x));
+}