DartType equals converted to operator == and tested.

lib/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.
 
 class LinkIterator<T> implements Iterator<T> {
   Link<T> current;
   LinkIterator(Link<T> this.current);
   bool hasNext() => !current.isEmpty();
   T next() {
     T result = current.head;
@@ skipping 53 matching lines @@
     if (from.isEmpty()) return this;
     return this.prepend(from.head).reversePrependAll(from.tail);
   }
 
   List toList() => const [];
 
   bool isEmpty() => true;
 
   void forEach(void f(T element)) {}
 
-  bool equals(other) {
+  bool operator ==(other) {
     if (other is !Link<T>) return false;
     return other.isEmpty();
   }
 }
 
 class LinkEntry<T> implements Link<T> {
   final T head;
   Link<T> tail;
 
   LinkEntry(T this.head, Link<T> this.tail);
@@ skipping 48 matching lines @@
     }
     return list;
   }
 
   void forEach(void f(T element)) {
     for (Link<T> link = this; !link.isEmpty(); link = link.tail) {
       f(link.head);
     }
   }
 
-  bool equals(other) {
+  bool operator ==(other) {
     if (other is !Link<T>) return false;
     Link<T> myElements = this;
     while (!myElements.isEmpty() && !other.isEmpty()) {
       if (myElements.head != other.head) {
         return false;
       }
       myElements = myElements.tail;
       other = other.tail;
     }
     return myElements.isEmpty() && other.isEmpty();
@@ skipping 20 matching lines @@
     length++;
     LinkEntry<T> entry = new LinkEntry<T>(t, null);
     if (head === null) {
       head = entry;
     } else {
       lastLink.tail = entry;
     }
     lastLink = entry;
   }
 }