Build script tags.

dart/frog/leg/scanner/scanner_task.dart

 // Copyright (c) 2011, 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 scan(CompilationUnitElement compilationUnit) {
     measure(() {
-      Link<Element> elements = scanElements(compilationUnit);
-      for (Link<Element> link = elements; !link.isEmpty(); link = link.tail) {
-        Element existing = compiler.universe.find(link.head.name);
-        if (existing !== null) {
-          Node node = link.head.parseNode(compiler, compiler);
-          // TODO(ahe): Is this the right place to handle this?
-          compiler.cancel('Duplicate definition', node: node);
-        }
-        compiler.universe.define(link.head);
+      scanElements(compilationUnit);
+      for (Element element in compilationUnit.topLevelElements) {
+        compiler.universe.define(element, compiler);
+      }
+      for (ScriptTag tag in compilationUnit.tags) {
+        compiler.reportWarning(tag, "library tags are not implemented");
       }
     });
   }
 
-  Link<Element> scanElements(CompilationUnitElement compilationUnit) {
+  void scanElements(CompilationUnitElement compilationUnit) {
     Script script = compilationUnit.script;
     Token tokens;
     try {
       tokens = new StringScanner(script.text).tokenize();
     } catch (MalformedInputException ex) {
       Token token;
       var message;
       if (ex.position is num) {
         // TODO(ahe): Always use tokens in MalformedInputException.
         token = new Token(EOF_INFO, ex.position);
       } else {
         token = ex.position;
       }
       compiler.cancel(ex.message, token: token);
     }
     ElementListener listener = new ElementListener(compiler, compilationUnit);
     PartialParser parser = new PartialParser(listener);
     parser.parseUnit(tokens);
-    return listener.topLevelElements;
   }
 }