New CSS parser written in Dart to replace pyparser

frog/tree.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.
 /**
  * The base type for all nodes in a dart abstract syntax tree.
  */
 class Node {
   /** The source code this [Node] represents. */
   SourceSpan span;
 
@@ skipping 61 matching lines @@
     }
     buf.add(s);
   }
 
   void writeln(String s) {
     write(s);
     buf.add('\n');
   }
 
   void heading(String name, span) {
-    buf.add(name);
+    write(name);
+    buf.add('  (${span.locationText})');
     buf.add('\n');
   }
 
   String toValue(value) {
     if (value == null) return 'null';
     else if (value is Identifier) return value.name;
     else return value.toString();
   }
 
   void writeNode(String label, Node node) {
@@ skipping 17 matching lines @@
     } else {
       for (var item in list) {
         buf.add(item.toString());
         buf.add(', ');
       }
       buf.add('\n');
     }
   }
 
   void writeNodeList(String label, List list) {
-    writeln(label + ':...');
+    writeln('${label} [');
     if (list != null) {
       depth += 1;
       for (var node in list) {
         if (node != null) {
           node.visit(printer);
         } else {
           writeln('null');
         }
       }
       depth -= 1;
+      writeln(']');
     }
   }
 }