Made dart2js constructor lookup logic "private"-aware, fixed 4740 bug.

lib/compiler/implementation/elements/elements.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.
 
 #library('elements');
 
 #import('dart:uri');
 
 #import('../tree/tree.dart');
 #import('../scanner/scannerlib.dart');
@@ skipping 1257 matching lines @@
     }
     SourceString fieldName = fieldMember.name;
     while (true) {
       Element foundMember = lookupClass.lookupMember(fieldName);
       if (foundMember == fieldMember) return false;
       if (foundMember.isField()) return true;
       lookupClass = foundMember.getEnclosingClass().superclass;
     }
   }
 
-  Element lookupConstructor(SourceString className,
+  Element lookupConstructor(LibraryElement fromLibrary,

[kasperl, 2012/09/19 05:59:17]

In general, I think we should start using selectors as keys for these kind of
lookups.

+                            SourceString className,
                             [SourceString constructorName =
                                  const SourceString(''),
                             Element noMatch(Element)]) {
     // TODO(karlklose): have a map from class names to a map of constructors
     //                  instead of creating the name here?
     SourceString normalizedName;
     if (constructorName !== const SourceString('')) {
       normalizedName = Elements.constructConstructorName(className,
                                                          constructorName);
     } else {
       normalizedName = className;
     }
     Element result = localLookup(normalizedName);
-    if (result === null || !result.isConstructor()) {
+    if (result === null
+        || !result.isConstructor()
+        || (constructorName.isPrivate()
+            && result.getLibrary() != fromLibrary)) {
       result = noMatch !== null ? noMatch(result) : null;
     }
     return result;
   }
 
   bool get hasConstructor {
     // Search in scope to be sure we search patched constructors.
     for (var element in localScope.getValues()) {
       if (element.isConstructor()) return true;
     }
@@ skipping 388 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }