Fix type warnings and a few other warnings, and probably even an error.

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 14 matching lines @@
       if (printDebugInfo) sb.add(']');
     } else if (printDebugInfo) {
       sb.add('[null]');
     }
   }
 
   visitBlock(Block node) {
     visit(node.statements);
   }
 
+  visitCascade(Cascade node) {
+    visit(node.expression);
+  }
+
+  visitCascadeReceiver(CascadeReceiver node) {
+    visit(node.expression);
+  }
+
   visitClassNode(ClassNode node) {
     node.beginToken.value.printOn(sb);
     sb.add(' ');
     visit(node.name);
     sb.add(' ');
     if (node.extendsKeyword !== null) {
       node.extendsKeyword.value.printOn(sb);
       sb.add(' ');
       visit(node.superclass);
       sb.add(' ');
@@ skipping 348 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }