Fix unparse for empty initializer or conditionStatement.

lib/compiler/implementation/tree/unparser.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.
 
 class Unparser implements Visitor {
   StringBuffer sb;
   final bool printDebugInfo;
 
   Unparser([this.printDebugInfo = false]);
 
@@ skipping 58 matching lines @@
   }
 
   visitExpressionStatement(ExpressionStatement node) {
     visit(node.expression);
     add(node.endToken.value);
   }
 
   visitFor(For node) {
     add(node.forToken.value);
     sb.add('(');
-    visit(node.initializer);
-    visit(node.conditionStatement);
+    visitPart(part) {

[Anton Muhin, 2012/06/07 15:31:29]

another option would be to yield empty statements out of parser for those.

+      if (part === null) {
+        sb.add(';');
+      } else {
+        visit(part);
+      }
+    }
+    visitPart(node.initializer);
+    visitPart(node.conditionStatement);
     visit(node.update);
     sb.add(')');
     visit(node.body);
   }
 
   visitFunctionDeclaration(FunctionDeclaration node) {
     visit(node.function);
   }
 
   visitFunctionExpression(FunctionExpression node) {
@@ skipping 347 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }