Fix for bug 1229: Unary operator plus is not allowed ... except for literals.

tests/language/src/LiteralUnaryPlusTest.dart

Index: tests/language/src/LiteralUnaryPlusTest.dart
===================================================================
--- tests/language/src/LiteralUnaryPlusTest.dart	(revision 0)
+++ tests/language/src/LiteralUnaryPlusTest.dart	(revision 0)
@@ -0,0 +1,15 @@
+// Copyright (c) 2012, 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.
+
+// There is no unary plus operator in Dart.
+// Only a number literal can be preceded by a "+'".
+
+main() {
+  var a = + 1;       /// 01: compile-time error
+  var x = +"foo";    /// 02: compile-time error
+  var x = + "foo";   /// 03: compile-time error
+  var z = +12;
+  var y = +.2;
+}
+