Fix type of String.fromEnvironment() when the name is undefined.

pkg/analyzer/lib/src/generated/constant.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.constant;
 
 import 'dart:collection';
@@ skipping 2407 matching lines @@
    * `null` if the variable is not defined. Return the value of the variable with the given
    * name interpreted as a String value. If the variable is not defined (or [variableName] is
    * null), a DartObject representing "unknown" is returned.
    *
    * @param typeProvider the type provider used to find the type 'String'
    * @param variableName the name of the variable whose value is to be returned
    */
   DartObject getString(TypeProvider typeProvider, String variableName) {
     String value = _declaredVariables[variableName];
     if (value == null) {
-      return new DartObjectImpl(typeProvider.intType, IntState.UNKNOWN_VALUE);
+      return new DartObjectImpl(typeProvider.stringType,
+          StringState.UNKNOWN_VALUE);
     }
     return new DartObjectImpl(typeProvider.stringType, new StringState(value));
   }
 }
 
 /**
  * Instances of the class `DoubleState` represent the state of an object representing a
  * double.
  */
 class DoubleState extends NumState {
@@ skipping 2248 matching lines @@
 
   @override
   String get typeName => "Type";
 
   @override
   int get hashCode => _element == null ? 0 : _element.hashCode;
 
   @override
   String toString() => _element == null ? "-unknown-" : _element.name;
 }