Change IllegalArgumentException to ArgumentError.

pkg/fixnum/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.
 
 /**
  * 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 {
 
@@ skipping 220 matching lines @@
     if (other is int64) {
       return (this.toInt64() ^ other).toInt32();
     }
     return new int32.fromInt(_i ^ _convert(other));
   }
 
   int32 operator ~() => new int32.fromInt(~_i);
 
   int32 operator <<(int n) {
     if (n < 0) {
-      throw new IllegalArgumentException("$n");
+      throw new ArgumentError("$n");
     }
     n &= 31;
     return new int32.fromInt(_i << n);
   }
 
   int32 operator >>(int n) {
     if (n < 0) {
-      throw new IllegalArgumentException("$n");
+      throw new ArgumentError("$n");
     }
     n &= 31;
     int value;
     if (_i >= 0) {
       value = _i >> n;
     } else {
       value = (_i >> n) | (0xffffffff << (32 - n));
     }
     return new int32.fromInt(value);
   }
 
   int32 shiftRightUnsigned(int n) {
     if (n < 0) {
-      throw new IllegalArgumentException("$n");
+      throw new ArgumentError("$n");
     }
     n &= 31;
     int value;
     if (_i >= 0) {
       value = _i >> n;
     } else {
       value = (_i >> n) & ((1 << (32 - n)) - 1);
     }
     return new int32.fromInt(value);
   }
@@ skipping 71 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);
 }