pkg/csslib: types, fixes, cleanup

pkg/csslib/lib/src/tree_base.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.
 
 part of csslib.visitor;
 
 /**
  * The base type for all nodes in a CSS abstract syntax tree.
  */
 abstract class TreeNode {
   /** The source code this [TreeNode] represents. */
-  Span span;
+  final Span span;
 
-  TreeNode(this.span) {}
+  TreeNode(this.span);
 
   TreeNode clone();
 
   /** Classic double-dispatch visitor for implementing passes. */
-  visit(VisitorBase visitor);
+  void visit(VisitorBase visitor);
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
     var to = new TreeOutput();
     var tp = new _TreePrinter(to, true);
     this.visit(tp);
     return to.buf.toString();
   }
 }
 
 /** The base type for expressions. */
 abstract class Expression extends TreeNode {
   Expression(Span span): super(span);
 }
 
 /** Simple class to provide a textual dump of trees for debugging. */
 class TreeOutput {
   int depth = 0;
   final StringBuffer buf = new StringBuffer();
-  var printer;
+  VisitorBase printer;
 
   void write(String s) {
     for (int i=0; i < depth; i++) {
       buf.write(' ');
     }
     buf.write(s);
   }
 
   void writeln(String s) {
     write(s);
@@ skipping 20 matching lines @@
     if (node != null) node.visit(printer);
     else writeln('null');
     depth -= 1;
   }
 
   void writeValue(String label, value) {
     var v = toValue(value);
     writeln('${label}: ${v}');
   }
 
-  void writeList(String label, List list) {
+  void writeList(String label, List<TreeNode> list) {
     write('${label}: ');
     if (list == null) {
       buf.write('null');
       buf.write('\n');
     } else {
       for (var item in list) {
         buf.write(item.toString());
         buf.write(', ');
       }
       buf.write('\n');
     }
   }
 
-  void writeNodeList(String label, List list) {
+  void writeNodeList(String label, List<TreeNode> list) {
     writeln('${label} [');
     if (list != null) {
       depth += 1;
       for (var node in list) {
         if (node != null) {
           node.visit(printer);
         } else {
           writeln('null');
         }
       }
       depth -= 1;
       writeln(']');
     }
   }
 
   String toString() => buf.toString();
 }