Support !=.

dart/frog/leg/resolver.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 TreeElements {
   Map<Node, Element> map;
   TreeElements() : map = new LinkedHashMap<Node, Element>();
   operator []=(Node node, Element element) => map[node] = element;
   operator [](Node node) => map[node];
 }
@@ skipping 245 matching lines @@
     if (name.stringValue === '&') return const SourceString('and');
     if (name.stringValue === '^') return const SourceString('xor');
 
     // Relational operators.
     if (name.stringValue === '<') return const SourceString('lt');
     if (name.stringValue === '<=') return const SourceString('le');
     if (name.stringValue === '>') return const SourceString('gt');
     if (name.stringValue === '>=') return const SourceString('ge');
 
     if (name.stringValue === '==') return const SourceString('eq');
+    if (name.stringValue === '!=') return const SourceString('eq');
 
     // Index operator.
     if (name.stringValue === '[]') return const SourceString('index');
-    unreachable();
+    compiler.unimplemented("mapOperatorToMethodName");
   }
 
   SourceString mapAssignmentOperatorToMethodName(SourceString name) {
     if (name.stringValue === '+=') return const SourceString('add');
     if (name.stringValue === '-=') return const SourceString('sub');
     if (name.stringValue === '*=') return const SourceString('mul');
     if (name.stringValue === '/=') return const SourceString('div');
     if (name.stringValue === '~/=') return const SourceString('tdiv');
     if (name.stringValue === '%=') return const SourceString('mod');
     if (name.stringValue === '<<=') return const SourceString('shl');
     if (name.stringValue === '>>=') return const SourceString('shr');
     if (name.stringValue === '|=') return const SourceString('or');
     if (name.stringValue === '&=') return const SourceString('and');
     if (name.stringValue === '^=') return const SourceString('xor');
     if (name.stringValue === '++') return const SourceString('add');
     if (name.stringValue === '--') return const SourceString('sub');
-    unreachable();
+    compiler.unimplemented("mapAssignmentOperatorToMethodName");
   }
 
   Element resolveSend(Send node) {
     Element receiver = visit(node.receiver);
     visit(node.argumentsNode);
 
     Identifier selector = node.selector;
     SourceString name = selector.source;
     // No need to assign an element for a logical operation.
     if (isLogicalOperator(selector)) return null;
@@ skipping 314 matching lines @@
 class TopScope extends Scope {
   Universe universe;
 
   TopScope(Universe this.universe) : super(null, null);
   Element lookup(SourceString name) => universe.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }