Fix most warnings and other minor cleanups.

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 visitCaseMatch(CaseMatch node);
@@ skipping 657 matching lines @@
 
   accept(Visitor visitor) => visitor.visitLiteralDouble(this);
 }
 
 class LiteralBool extends Literal<bool> {
   LiteralBool(Token token, DecodeErrorHandler handler) : super(token, handler);
 
   LiteralBool asLiteralBool() => this;
 
   bool get value() {
-    switch (token.value) {
-      case Keyword.TRUE: return true;
-      case Keyword.FALSE: return false;
-      default:
-        (this.handler)(token, "not a bool ${token.value}");
-    }
+    if (token.value == Keyword.TRUE) return true;
+    if (token.value == Keyword.FALSE) return false;
+    (this.handler)(token, "not a bool ${token.value}");
   }
 
   accept(Visitor visitor) => visitor.visitLiteralBool(this);
 }
 
 
 class StringQuoting {
   static final StringQuoting SINGLELINE_DQ =
       const StringQuoting($DQ, raw: false, leftQuoteLength: 1);
   static final StringQuoting RAW_SINGLELINE_DQ =
@@ skipping 1015 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);
 }