Make sure that libraries loaded from dart:core gets dart:core implicitly loaded.

lib/compiler/implementation/compiler.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.
 
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
 final bool REPORT_EXCESS_RESOLUTION = false;
@@ skipping 331 matching lines @@
     }
 
     jsIndexingBehaviorInterface =
         findHelper(const SourceString('JavaScriptIndexingBehavior'));
   }
 
   void scanBuiltinLibraries() {
     coreImplLibrary = scanBuiltinLibrary('coreimpl');
     jsHelperLibrary = scanBuiltinLibrary('_js_helper');
     interceptorsLibrary = scanBuiltinLibrary('_interceptors');
-    coreLibrary = scanBuiltinLibrary('core');
 
-    // Since coreLibrary import the libraries "coreimpl", "js_helper",
-    // and "interceptors", coreLibrary is null when they are being
-    // built. So we add the implicit import of coreLibrary now. This
-    // can be cleaned up when we have proper support for "dart:core"
-    // and don't need to access it through the field "coreLibrary".
-    // TODO(ahe): Clean this up as described above.
-    scanner.importLibrary(coreImplLibrary, coreLibrary, null);
-    scanner.importLibrary(jsHelperLibrary, coreLibrary, null);
-    scanner.importLibrary(interceptorsLibrary, coreLibrary, null);
     addForeignFunctions(jsHelperLibrary);
     addForeignFunctions(interceptorsLibrary);
 
     libraries['dart:core'] = coreLibrary;
     libraries['dart:coreimpl'] = coreImplLibrary;
 
     assertMethod = coreLibrary.find(const SourceString('assert'));
 
     initializeSpecialClasses();
 
     //patchDartLibrary(coreLibrary, 'core');
     //patchDartLibrary(coreImplLibrary, 'coreimpl');
   }
 
+  void importCoreLibrary(LibraryElement library) {
+    Uri coreUri = new Uri.fromComponents(scheme: 'dart', path: 'core');
+    if (coreLibrary === null) {
+      coreLibrary = scanner.loadLibrary(coreUri, null, coreUri);
+    }
+    scanner.importLibrary(library,
+                          coreLibrary,
+                          null,
+                          library.entryCompilationUnit);
+  }
+
   void patchDartLibrary(LibraryElement library, String dartLibraryPath) {
     if (library.isPatched) return;
     Uri patchUri = resolvePatchUri(dartLibraryPath);
     if (patchUri !== null) {
        patchParser.patchLibrary(patchUri, library);
       // We allow foreign functions in patched libraries.
       addForeignFunctions(library);  // Is safe even if already added.
       // TODO(lrn): Make this lazy.
       applyClassPatches(library);
     }
@@ skipping 548 matching lines @@
     final endOffset = end.charOffset + end.slowCharCount;
 
     // [begin] and [end] might be the same for the same empty token. This
     // happens for instance when scanning '$$'.
     assert(endOffset >= beginOffset);
     return f(beginOffset, endOffset);
   }
 
   String toString() => 'SourceSpan($uri, $begin, $end)';
 }