Only generate assert in checked mode.

lib/compiler/implementation/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Type getType(TypeAnnotation annotation);
 }
 
@@ skipping 1034 matching lines @@
       mapping.setSelector(node, Selector.INDEX);
     } else if (node.isPropertyAccess) {
       mapping.setSelector(node, Selector.GETTER);
     } else {
       handleArguments(node);
     }
     if (target != null && target.kind == ElementKind.ABSTRACT_FIELD) {
       AbstractFieldElement field = target;
       target = field.getter;
     }
+    if (target == compiler.assertMethod && !node.isCall) {

[kasperl, 2012/06/08 05:34:05]

===

[ngeoffray, 2012/06/08 09:40:58]

Done.

+      // We can only use assert by calling it.
+      if (!inInstanceContext) error(node, MessageKind.CANNOT_RESOLVE, [node]);

[ahe, 2012/06/08 07:59:14]

I'm not sure about this error message.

I think it is more likely that the user is using assert incorrectly, so saying
something like "missing arguments to assert".

[ngeoffray, 2012/06/08 09:40:58]

Done.

+      target = null;
+    }
     // TODO(ngeoffray): Warn if target is null and the send is
     // unqualified.
     useElement(node, target);
     if (node.isPropertyAccess) return target;
   }
 
   visitSendSet(SendSet node) {
     Element target = resolveSend(node);
     Element setter = null;
     Element getter = null;
@@ skipping 939 matching lines @@
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) {
     return library.find(name);
   }
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";
   }
 }