Fix most warnings and other minor cleanups.

lib/compiler/implementation/tree/nodes.dart

Index: lib/compiler/implementation/tree/nodes.dart
diff --git a/lib/compiler/implementation/tree/nodes.dart b/lib/compiler/implementation/tree/nodes.dart
index 3444c1f8e6b046fde5f1c0ae7a1998d0d7792187..fa36ce4cddb9e200eb68fc175d4c662a8f5fed9c 100644
--- a/lib/compiler/implementation/tree/nodes.dart
+++ b/lib/compiler/implementation/tree/nodes.dart
@@ -675,12 +675,9 @@ class LiteralBool extends Literal<bool> {
   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);