Parse/unparse library combinators.

dart/lib/compiler/implementation/scanner/scanner_task.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.
 
 class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name => 'Scanner';
 
   void scanLibrary(LibraryElement library) {
     var compilationUnit = library.entryCompilationUnit;
@@ skipping 22 matching lines @@
         return tagState;
       }
       return TagState.NEXT[value];
     }
 
     LinkBuilder<Import> imports = new LinkBuilder<Import>();
     Uri base = library.entryCompilationUnit.script.uri;
     for (LibraryTag tag in library.tags.reverse()) {
       if (tag.isImport) {
         tagState = checkTag(TagState.IMPORT, tag);
+        if (tag.combinators != null) {
+          compiler.unimplemented('combinators', node: tag.combinators);
+        }
         // It is not safe to import other libraries at this point as
         // another library could then observe the current library
         // before it fully declares all the members that are sourced
         // in.
         imports.addLast(tag);
       } else if (tag.isLibraryName) {
         tagState = checkTag(TagState.LIBRARY, tag);
         if (library.libraryTag !== null) {
           compiler.cancel("duplicated library declaration", node: tag);
         } else {
@@ skipping 156 matching lines @@
   static const int RESOURCE = 4;
 
   /** Next state. */
   static const List<int> NEXT =
       const <int>[NO_TAG_SEEN,
                   IMPORT, // Only one library tag is allowed.
                   IMPORT,
                   SOURCE,
                   RESOURCE];
 }