move csslib into dart svn

pkg/csslib/lib/src/tree_base.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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 dart abstract syntax tree.
+ * The base type for all nodes in a CSS abstract syntax tree.
  */
-class ASTNode {
-  /** The source code this [ASTNode] represents. */
-  SourceSpan span;
+abstract class TreeNode {
+  /** The source code this [TreeNode] represents. */
+  Span span;
 
-  ASTNode(this.span) {}
+  TreeNode(this.span) {}
 
   /** Classic double-dispatch visitor for implementing passes. */
-  abstract visit(TreeVisitor visitor);
+  visit(VisitorBase visitor);
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
     var to = new TreeOutput();
-    var tp = new TreePrinter(to);
+    var tp = new _TreePrinter(to, true);
     this.visit(tp);
     return to.buf.toString();
   }
 }
 
-// TODO(jimhug): Clean-up and factor out of core.
+/** 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;
-  StringBuffer buf;
-
+  int depth = 0;
+  final StringBuffer buf = new StringBuffer();
   var printer;
 
-  static void dump(ASTNode node) {
-    var o = new TreeOutput();
-    node.visit(new TreePrinter(o));
-    print(o.buf);
-  }
-
-  TreeOutput(): this.depth = 0, this.buf = new StringBuffer() {
-  }
-
   void write(String s) {
     for (int i=0; i < depth; i++) {
       buf.write(' ');
     }
     buf.write(s);
   }
 
   void writeln(String s) {
-    buf.writeln(s);
+    write(s);
+    buf.write('\n');
   }
 
-  void heading(String name, span) {
+  void heading(String name, [span]) {
     write(name);
-    buf.writeln('  (${span.locationText})');
+    if (span != null) {
+      buf.write('  (${span.getLocationMessage('')})');
+    }
+    buf.write('\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, ASTNode node) {
-    write(label + ': ');
+  void writeNode(String label, TreeNode node) {
+    write('${label}: ');
     depth += 1;
     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) {
-    write(label + ': ');
+    write('${label}: ');
     if (list == null) {
-      buf.writeln('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) {
     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();
 }