IllegalArgumentException expects a string.

runtime/lib/growable_array.dart

 // Copyright (c) 2011, 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.
 
 class GrowableObjectArray<T> implements Array<T> {
   Array<T> backingArray;
 
   void copyFrom(Array<Object> src, int srcStart, int dstStart, int count) {
     Arrays.copy(src, srcStart, this, dstStart, count);
   }
 
   void setRange(int start, int length, List<T> from, [int startFrom = 0]) {
-    if (length < 0) throw new IllegalArgumentException(length);
+    if (length < 0) {
+      throw new IllegalArgumentException("negative length $length");
+    }
     Arrays.copy(from, startFrom, this, start, length);
   }
 
   void removeRange(int start, int length) {
     if (length == 0) {
       return;
     }
     if (length < 0) {
-      throw const IllegalArgumentException();
+      throw new IllegalArgumentException("negative length $length");
     }
     if (start < 0 || start >= this.length) {
       throw new IndexOutOfRangeException(start);
     }
     if (start + length > this.length) {
       throw new IndexOutOfRangeException(start + length);
     }
     Arrays.copy(backingArray,
                 start + length,
                 backingArray,
@@ skipping 174 matching lines @@
     if (!hasNext()) {
       throw const NoMoreElementsException();
     }
     return _array[_pos++];
   }
 
   final GrowableObjectArray<T> _array;
   int _pos;
 }