Added support for exports and re-exports.

lib/compiler/implementation/elements/elements.dart

Index: lib/compiler/implementation/elements/elements.dart
diff --git a/lib/compiler/implementation/elements/elements.dart b/lib/compiler/implementation/elements/elements.dart
index 3775bc740d446d42d288da93064db6a366e48a8f..9a077b51df57da52da3e61ea10077e097d4d7b13 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -104,6 +104,9 @@ class ElementKind {
   static const ElementKind VOID =
     const ElementKind('void', ElementCategory.NONE);
 
+  static const ElementKind ERRONEOUS =

[Lasse Reichstein Nielsen, 2012/09/28 07:45:36]

It should be called ERROR - a noun - and not ERRONEOUS - an adjective.
It represents an error condition. It does so correctly, not erroneously.

[Johnni Winther, 2012/10/09 09:47:10]

Done.

+      const ElementKind('erroneous', ElementCategory.NONE);
+
   toString() => id;
 }
 
@@ -371,7 +374,8 @@ class ErroneousElement extends Element {
 
   ErroneousElement(this.messageKind, this.messageArguments,
                    this.targetName, Element enclosing)
-      : super(const SourceString('erroneous element'), null, enclosing);
+      : super(const SourceString('erroneous element'),
+              ElementKind.ERRONEOUS, enclosing);
 
   isErroneous() => true;
 
@@ -380,7 +384,6 @@ class ErroneousElement extends Element {
   }
 
   SourceString get name => unsupported();
-  ElementKind get kind => unsupported();
   Link<MetadataAnnotation> get metadata => unsupported();
 
   getLibrary() => enclosingElement.getLibrary();
@@ -550,6 +553,25 @@ class LibraryElement extends ScopeContainerElement {
    */
   final Map<SourceString, Element> importScope;
 
+  /**
+   * Map for elements exported either through export declarations or through
+   * declaration.
+   *
+   * [ImportExportHandler] sets this map when the library is loaded.
+   */
+  Map<SourceString, Element> _exportScope;
+
+  Map<SourceString, Element> get exportScope {

[Lasse Reichstein Nielsen, 2012/09/28 07:45:36]

Please don't export the map. Someone will just do bad stuff to it. Can you wrap
it in something opaque that only exposes simple lookup and foreach operations?

[Bob Nystrom, 2012/09/28 16:41:27]

Drive-by comment: I see stuff like this frequently. It makes me wonder if we
should have better support for providing read-only access to collections.

[Johnni Winther, 2012/10/09 09:47:10]

Changed to used a linked list.

+    assert(invariant(this, _exportScope !== null));
+    return _exportScope;
+  }
+
+  void set exportScope(Map<SourceString, Element> map) {
+    assert(invariant(this, _exportScope === null));
+    assert(invariant(this, map !== null));
+    _exportScope = map;
+  }
+
   LibraryElement(Script script, [Uri uri])
     : this.uri = ((uri === null) ? script.uri : uri),
       importScope = new Map<SourceString, Element>(),
@@ -557,7 +579,6 @@ class LibraryElement extends ScopeContainerElement {
     entryCompilationUnit = new CompilationUnitElement(script, this);
   }
 
-
   bool get isPatched => patch !== null;
 
   void addCompilationUnit(CompilationUnitElement element) {
@@ -576,19 +597,19 @@ class LibraryElement extends ScopeContainerElement {
    * detection of ambiguous uses of imported names.
    */
   void addImport(Element element, DiagnosticListener listener) {
-    Element existing = importScope.putIfAbsent(element.name, () => element);
+    SourceString name = element.name;
+    Element existing = importScope.putIfAbsent(name, () => element);
     if (existing !== element && existing !== null) {

[Lasse Reichstein Nielsen, 2012/09/28 07:45:36]

Add a comment that you are not following the current spec here by testing for
(existing !== element). Importing the same element twice is specified as an
error.

[Johnni Winther, 2012/10/09 09:47:10]

Implementation changed to follow spec.

       if (!existing.isErroneous()) {
         // TODO(johnniwinther): Provide access to both the new and existing
         // elements.
-        importScope[element.name] = new ErroneousElement(
+        importScope[name] = new ErroneousElement(
             MessageKind.DUPLICATE_IMPORT,
-            [element.name], element.name, this);
+            [name], name, this);
       }
     }
   }
 
-
   /**
    * Look up a top-level element in this library. The element could
    * potentially have been imported from another library. Returns
@@ -620,6 +641,7 @@ class LibraryElement extends ScopeContainerElement {
         f(e);
       }
     });
+    exportScope.forEach((_, Element e) => f(e));
   }
 
   bool hasLibraryName() => libraryTag !== null;