Int32 constants should be const.

pkg/fixnum/lib/src/int32.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 fixnum;
 
 /**
  * An immutable 32-bit signed integer, in the range [-2^31, 2^31 - 1].
  * Arithmetic operations may overflow in order to maintain this range.
  */
 class Int32 implements IntX {
 
   /**
    * The maximum positive value attainable by an [Int32], namely
    * 2147483647.
    */
   static const Int32 MAX_VALUE = const Int32._internal(0x7FFFFFFF);
 
   /**
    * The minimum positive value attainable by an [Int32], namely
    * -2147483648.
    */
-  static Int32 MIN_VALUE = const Int32._internal(-0x80000000);
+  static const Int32 MIN_VALUE = const Int32._internal(-0x80000000);
 
   /**
    * An [Int32] constant equal to 0.
    */
-  static Int32 ZERO = const Int32._internal(0);
+  static const Int32 ZERO = const Int32._internal(0);
 
   /**
    * An [Int32] constant equal to 1.
    */
-  static Int32 ONE = const Int32._internal(1);
+  static const Int32 ONE = const Int32._internal(1);
 
   /**
    * An [Int32] constant equal to 2.
    */
-  static Int32 TWO = const Int32._internal(2);
+  static const Int32 TWO = const Int32._internal(2);
 
   // Hex digit char codes
   static const int _CC_0 = 48; // '0'.codeUnitAt(0)
   static const int _CC_9 = 57; // '9'.codeUnitAt(0)
   static const int _CC_a = 97; // 'a'.codeUnitAt(0)
   static const int _CC_z = 122; // 'z'.codeUnitAt(0)
   static const int _CC_A = 65; // 'A'.codeUnitAt(0)
   static const int _CC_Z = 90; // 'Z'.codeUnitAt(0)
 
   static int _decodeHex(int c) {
@@ skipping 294 matching lines @@
   }
 
   int toInt() => _i;
   Int32 toInt32() => this;
   Int64 toInt64() => new Int64.fromInt(_i);
 
   String toString() => _i.toString();
   String toHexString() => _i.toRadixString(16);
   String toRadixString(int radix) => _i.toRadixString(radix);
 }