Clean up exceptions thrown in pkg/fixnum.

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.
  */
@@ skipping 46 matching lines @@
     }
   }
 
   /**
    * Parses a [String] in a given [radix] between 2 and 16 and returns an
    * [Int32].
    */
   // TODO(rice) - Make this faster by converting several digits at once.
   static Int32 parseRadix(String s, int radix) {
     if ((radix <= 1) || (radix > 16)) {
-      throw "Bad radix: $radix";
+      throw new ArgumentError("Bad radix: $radix");
     }
     Int32 x = ZERO;
     for (int i = 0; i < s.length; i++) {
       int c = s.codeUnitAt(i);
       int digit = _decodeHex(c);
       if (digit < 0 || digit >= radix) {
         throw new Exception("Non-radix code unit: $c");
       }
       x = (x * radix) + digit;
     }
@@ skipping 150 matching lines @@
     if (other is Int64) {
       return (this.toInt64() ^ other).toInt32();
     }
     return new Int32.fromInt(_i ^ _toInt(other));
   }
 
   Int32 operator ~() => new Int32.fromInt(~_i);
 
   Int32 operator <<(int n) {
     if (n < 0) {
-      throw new ArgumentError("$n");
+      throw new ArgumentError(n);
     }
     n &= 31;
     return new Int32.fromInt(_i << n);
   }
 
   Int32 operator >>(int n) {
     if (n < 0) {
-      throw new ArgumentError("$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 ArgumentError("$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 72 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);
 }