Add ImportElement and ExportElement

pkg/compiler/lib/src/dart_backend/outputter.dart

 // Copyright (c) 2014, 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.
 
 part of dart_backend;
 
 typedef bool IsSafeToRemoveTypeDeclarations(
     Map<ClassElement, Iterable<Element>> classMembers);
 typedef void ElementCallback<E>(E element);
 typedef void ElementPostProcessFunction(
@@ skipping 249 matching lines @@
             }
           });
         }
         // Even class names are added due to a delicate problem we have:
         // if one imports dart:core with a prefix, we cannot tell prefix.name
         // from dynamic invocation (alas!).  So we'd better err on preserving
         // those names.
         fixedStaticNames.add(element.name);
       });
 
-      for (Element export in library.exports) {
+      library.forEachExport((Element export) {
         if (!library.isInternalLibrary &&
             export.library.isInternalLibrary) {
           // If an element of an internal library is reexported by a platform
           // library, we have to import the reexporting library instead of the
           // internal library, because the internal library is an
           // implementation detail of dart2js.
           reexportingLibraries[export] = library;
         }
-      }
+      });
     }
 
     // Map to keep track of names of enum classes. Since these cannot be renamed
     // we ensure that they are unique.
     Map<String, ClassElement> enumClassMap = <String, ClassElement>{};
 
     // As of now names of named optionals are not renamed. Therefore add all
     // field names used as named optionals into [fixedMemberNames].
     for (final element in resolvedElements) {
       if (!element.isConstructor) continue;
@@ skipping 229 matching lines @@
         }
       }
 
       /// Rewrites imports/exports to refer to the paths given in [outputPaths].
       for(LibraryElement outputLibrary in libraryInfo.userLibraries) {
         EmitterUnparser unparser = new EmitterUnparser(
             placeholderRenamer.renames,
             stripTypes: forceStripTypes,
             minify: enableMinification);
         unparsers[outputLibrary] = unparser;
-        LibraryName libraryName = outputLibrary.libraryTag;
-        if (libraryName != null) {
-          unparser.visitLibraryName(libraryName);
+        if (outputLibrary.hasLibraryName) {
+          unparser.unparseLibraryName(outputLibrary.libraryName);
         }
-        for (LibraryTag tag in outputLibrary.tags) {
-          if (tag is! LibraryDependency) continue;
-          LibraryDependency dependency = tag;
-          LibraryElement libraryElement =
-              outputLibrary.getLibraryFromTag(dependency);
+        for (ImportElement import in outputLibrary.imports) {
+          LibraryElement libraryElement = import.importedLibrary;
           String uri = outputPaths.containsKey(libraryElement)
               ? "${outputPaths[libraryElement]}.dart"
               : libraryElement.canonicalUri.toString();
-          if (dependency is Import) {
-            unparser.unparseImportTag(uri);
-          } else {
-            unparser.unparseExportTag(uri);
-          }
+          unparser.unparseImportTag(uri);
+        }
+        for (ExportElement export in outputLibrary.exports) {
+          LibraryElement libraryElement = export.exportedLibrary;
+          String uri = outputPaths.containsKey(libraryElement)
+              ? "${outputPaths[libraryElement]}.dart"
+              : libraryElement.canonicalUri.toString();
+          unparser.unparseExportTag(uri);
         }
       }
     } else {
       placeholderRenamer.platformImports.forEach(
           (LibraryElement library, String prefix) {
         assert(library.isPlatformLibrary && !library.isInternalLibrary);
         mainUnparser.unparseImportTag(library.canonicalUri.toString());
         if (prefix != null) {
           // Adding a prefixed import because (some) top-level access need
           // it to avoid shadowing.
@@ skipping 33 matching lines @@
       outputProvider("", "dart")
            ..add(code)
            ..close();
 
       totalSize = code.length;
     }
 
     return totalSize;
   }
 }