Report arity errors on user definable operators.

sdk/lib/_internal/compiler/implementation/util/link_implementation.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.
 
 part of util_implementation;
 
 class LinkIterator<T> implements Iterator<T> {
   T _current;
   Link<T> _link;
 
@@ skipping 50 matching lines @@
   }
 
   Link<T> reversePrependAll(Link<T> from) {
     Link<T> result;
     for (result = this; !from.isEmpty; from = from.tail) {
       result = result.prepend(from.head);
     }
     return result;
   }
 
+  Link<T> skip(int n) {
+    Link<T> link = this;
+    for (int i = 0 ; i < n ; i++) {
+      if (link.isEmpty) {
+        throw new RangeError('Index $n out of range');
+      }
+      link = link.tail;
+    }
+    return link;
+  }
 
   bool get isEmpty => false;
 
   List<T> toList() {
     List<T> list = new List<T>();
     for (Link<T> link = this; !link.isEmpty; link = link.tail) {
       list.addLast(link.head);
     }
     return list;
   }
@@ skipping 40 matching lines @@
     if (head == null) {
       head = entry;
     } else {
       lastLink.tail = entry;
     }
     lastLink = entry;
   }
 
   bool get isEmpty => length == 0;
 }