Implement fromEnvironment on bool, int and String

sdk/lib/core/int.dart

 // 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.
 
 part of dart.core;
 
 /**
  * An arbitrarily large integer.
  *
  * **Note:** When compiling to JavaScript, integers are
@@ skipping 234 matching lines @@
    * sign, the [onError] is called with the [source] as argument, and its return
    * value is used instead. If no [onError] is provided, a [FormatException]
    * is thrown.
    *
    * The [onError] function is only invoked if [source] is a [String]. It is
    * not invoked if the [source] is, for example, `null`.
    */
   external static int parse(String source,
                             { int radix,
                               int onError(String source) });
+
+  /**

[Lasse Reichstein Nielsen, 2013/10/31 06:55:38]

Comments need reformatting. I'll look at it today.

+   * Returns the integer value for the given environment variable
+   * [name] or [defaultValue] if [name] is not present. If the value
+   * of the environment variable is not a valid integer literal a
+   * [FormatException] is thrown.
+   */
+  external const factory int.fromEnvironment(String name, {int defaultValue});
 }