runtime/lib/symbol_patch.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.

patch class Symbol {
  /* patch */ const Symbol(String name)
      : this._name = _validate(name);

  static final RegExp _validationPattern =
      new RegExp(r'^(?:[a-zA-Z$][a-zA-Z$0-9_]*\.)*(?:[a-zA-Z$][a-zA-Z$0-9_]*=?|'
                 r'-|'
                 r'unary-|'
                 r'\[\]=|'
                 r'~|'
                 r'==|'
                 r'\[\]|'
                 r'\*|'
                 r'/|'
                 r'%|'
                 r'~/|'
                 r'\+|'
                 r'<<|'
                 r'>>|'
                 r'>=|'
                 r'>|'
                 r'<=|'
                 r'<|'
                 r'&|'
                 r'\^|'
                 r'\|'
                 r')$');

  static _validate(String name) {
    if (name is! String) throw new ArgumentError('name must be a String');
    if (name.isEmpty) return name;
    if (name.startsWith('_')) {
      throw new ArgumentError('"$name" is a private identifier');
    }
    if (!_validationPattern.hasMatch(name)) {
      throw new ArgumentError(
          '"$name" is not an identifier or an empty String');
    }
    return name;
  }
}