Create a DOM node for each token to ensure more precise diagnostics.

dart/site/try/src/editor.dart

 // Copyright (c) 2013, 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.
 
 library trydart.editor;
 
 import 'dart:html';
 
 import '../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart'
   show
@@ skipping 223 matching lines @@
       if (anchorNode == node) {
         hasSelection = true;
         anchorOffset = selection.anchorOffset + offset;
       }
       int newOffset = offset + cdata.length;
       if (offset <= begin && begin < newOffset) {
         hasSelection = node == anchorNode;
         anchorOffset = selection.anchorOffset;
         Node marker = new Text("");
         node.replaceWith(marker);
-        // TODO(ahe): Don't highlight everything in the node.  Find
-        // the relevant token.
+        // TODO(ahe): Don't highlight everything in the node.  Find the
+        // relevant token (works for now as we create a node for each token,
+        // which is probably not great for performance).
         if (kind == 'error') {
           marker.replaceWith(diagnostic(node, error(message)));
         } else if (kind == 'warning') {
           marker.replaceWith(diagnostic(node, warning(message)));
         } else {
           marker.replaceWith(diagnostic(node, info(message)));
         }
         if (hasSelection) {
           selection.collapse(node, anchorOffset);
         }
@@ skipping 38 matching lines @@
   String tokenValue = token.value;
   String tokenInfo = token.info.value;
   if (tokenInfo == 'string') return currentTheme.string;
   // if (tokenInfo == 'identifier') return identifier;
   if (tokenInfo == 'keyword') return currentTheme.keyword;
   if (tokenInfo == 'comment') return currentTheme.singleLineComment;
   if (tokenInfo == 'malformed input') {
     isMalformedInput = true;
     return new DiagnosticDecoration('error', tokenValue);
   }
-  return null;
+  return currentTheme.foreground;
 }
 
 diagnostic(text, tip) {
   if (text is String) {
     text = new Text(text);
   }
   return new AnchorElement()
       ..classes.add('diagnostic')
       ..append(text)
       ..append(tip);
 }