Unresolved super-send is not a compile-time error.

dart/frog/leg/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);
 }
 
 class TreeElementMapping implements TreeElements {
@@ skipping 705 matching lines @@
     SourceString name = node.selector.asIdentifier().source;
     if (node.isSuperCall) {
       if (isUserDefinableOperator(name.stringValue)) {
         name = Elements.constructOperatorName(const SourceString('operator'),
                                               name);
       }
       if (!inInstanceContext) {
         error(node.receiver, MessageKind.NO_INSTANCE_AVAILABLE, [name]);
         return null;
       }
+      if (currentClass.supertype === null) {
+        // This is just to guard against internal errors, so no need
+        // for a real error message.
+        error(node.receiver, MessageKind.GENERIC, "Object has no superclass");
+      }
       target = currentClass.lookupSuperMember(name);
-      if (target === null) {
-        error(node.selector, MessageKind.METHOD_NOT_FOUND,
-              [currentClass.superclass.name, name]);
-      }
+      // [target] may be null which means invoking noSuchMethod on
+      // super.

[ngeoffray, 2012/03/13 11:32:30]

No warning?

     } else if (resolvedReceiver === null) {
       return null;
     } else if (resolvedReceiver.kind === ElementKind.CLASS) {
       ClassElement receiverClass = resolvedReceiver;
       target = receiverClass.ensureResolved(compiler).lookupLocalMember(name);
       if (target === null) {
         error(node, MessageKind.METHOD_NOT_FOUND, [receiverClass.name, name]);
       } else if (target.isInstanceMember()) {
         error(node, MessageKind.MEMBER_NOT_STATIC, [receiverClass.name, name]);
       }
@@ skipping 817 matching lines @@
 class TopScope extends Scope {
   LibraryElement get library() => element;
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) => library.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }