Add validation of private symbols to the dart2js mirrors.

tests/lib/mirrors/symbol_validation_test.dart

 // 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.
 
 library symbol_validation_test;
 
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 validSymbol(String string) {
   Expect.equals(string,
                 MirrorSystem.getName(new Symbol(string)),
                 'Valid symbol "$string" should be invertable');
-  return;  /// 01: ok
   Expect.equals(string,
                 MirrorSystem.getName(MirrorSystem.getSymbol(string)),
                 'Valid symbol "$string" should be invertable');
 }
 
 invalidSymbol(String string) {
   Expect.throws(() => new Symbol(string),
                 (e) => e is ArgumentError,
                 'Invalid symbol "$string" should be rejected');
-  return;  /// 01: continued
   Expect.throws(() => MirrorSystem.getSymbol(string),
-               (e) => e is ArgumentError,
+                (e) => e is ArgumentError,
                 'Invalid symbol "$string" should be rejected');
 }
 
+validPrivateSymbol(String string) {
+  ClosureMirror closure = reflect(main);
+  LibraryMirror library = closure.function.owner;
+  Expect.equals(string,
+                MirrorSystem.getName(MirrorSystem.getSymbol(string, library)),
+                'Valid private symbol "$string" should be invertable');
+}
+
 main() {
   // Operators that can be declared as class member operators.
   // These are all valid as symbols.
   var operators = [
     '%', '&', '*', '+', '-', '/', '<', '<<', '<=', '==', '>',
     '>=', '>>', '[]', '[]=', '^', 'unary-', '|', '~', '~/'
   ];
   operators.expand((op) => [op, "x.$op"]).forEach(validSymbol);
   operators.expand((op) => [".$op", "$op.x", "x$op", "_x.$op"])
            .forEach(invalidSymbol);
   operators.expand((op) => operators.contains("$op=") ? [] : ["x.$op=", "$op="])
            .forEach(invalidSymbol);
 
   var simpleSymbols = [
     'foo', 'bar_', 'baz.quz', 'fisk1', 'hest2fisk', 'a.b.c.d.e',
     r'$', r'foo$', r'bar$bar', r'$.$', r'x6$_', r'$6_', r'x.$$6_',
-    'x_', 'x_.x_',
+    'x_', 'x_.x_', 'unary', 'x.unary'
   ];
   simpleSymbols.expand((s) => [s, "s="]).forEach(validSymbol);
 
   var nonSymbols = [
     // Non-identifiers.
     '6', '0foo', ',', 'S with M', '_invalid&private', "#foo", " foo", "foo ",
     // Operator variants.
     '+=', '()', 'operator+', 'unary+', '>>>', "&&", "||", "!", "@", "#", "[",
     // Private symbols.
     '_', '_x', 'x._y', 'x._',
@@ skipping 58 matching lines @@
     "library",
     "operator",
     "part",
     "set",
     "static",
     "typedef"
   ];
   builtInIdentifiers.expand((w) => [w, "$w=", "x.$w" , "$w.x", "x.$w.x",
                                     "$w=", "x.$w="])
                     .forEach(validSymbol);
+
+  var privateSymbols = [
+    '_', '_x', 'x._y', 'x._', 'x.y._', 'x._.y', '_true'
+  ];
+  privateSymbols.forEach(invalidSymbol);
+  privateSymbols.forEach(validPrivateSymbol);   /// 01: ok
 }