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

lib/compiler/implementation/tree/nodes.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.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCascade(Cascade node);
   R visitCascadeReceiver(CascadeReceiver node);
   R visitCatchBlock(CatchBlock node);
@@ skipping 1354 matching lines @@
       return statements.getEndToken();
     }
   }
 
   Link<Token> caseKeywords() {
     Token token = startToken;
     if (label !== null) {
       // Skip past the label: <Identifier> ':'.
       token = token.next.next;
     }
-    Link<Token> recursiveGetCases(Token token, Link<Expression> expressions) {
-      if (token.stringValue === 'case') {
-        Token colon = expressions.head.getEndToken().next;
-        return new Link<Token>(token,
-                               recursiveGetCases(colon.next, expressions.tail));
-      }
-      return const EmptyLink<Token>();
+    LinkBuilder<Token> builder = new LinkBuilder<Token>();
+    Link<Expression> link = expressions.nodes;
+    while (token.stringValue === 'case') {
+      assert(token.next === link.head.getBeginToken(0));
+      builder.addLast(token);
+      Token colon = link.head.getEndToken().next;
+      token = colon.next;
+      link = link.tail;
     }
-    return recursiveGetCases(token, expressions.nodes);
+    return builder.toLink();
   }
 }
 
 class GotoStatement extends Statement {
   final Identifier target;
   final Token keywordToken;
   final Token semicolonToken;
 
   GotoStatement(this.target, this.keywordToken, this.semicolonToken);
 
@@ skipping 167 matching lines @@
 
   Token getBeginToken() => tryKeyword;
 
   Token getEndToken() {
     if (finallyBlock !== null) return finallyBlock.getEndToken();
     if (!catchBlocks.isEmpty()) return catchBlocks.getEndToken();
     return tryBlock.getEndToken();
   }
 }
 
-class Cascade extends Node {
-  final Node expression;
+class Cascade extends Expression {
+  final Expression expression;
   Cascade(this.expression);
 
   Cascade asCascade() => this;
   accept(Visitor visitor) => visitor.visitCascade(this);
 
   void visitChildren(Visitor visitor) {
     expression.accept(visitor);
   }
 
   Token getBeginToken() => expression.getBeginToken();
 
   Token getEndToken() => expression.getEndToken();
 }
 
-class CascadeReceiver extends Node {
-  final Node expression;
+class CascadeReceiver extends Expression {
+  final Expression expression;
   final Token cascadeOperator;
   CascadeReceiver(this.expression, this.cascadeOperator);
 
   CascadeReceiver asCascadeReceiver() => this;
   accept(Visitor visitor) => visitor.visitCascadeReceiver(this);
 
   void visitChildren(Visitor visitor) {
     expression.accept(visitor);
   }
 
@@ skipping 81 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send !== null) return f(send.arguments.head);
 }