anchor.diff:  }
   
   /**
  - * Used to mark scope exit.
  + * Used to mark scope exit. [scope] is the return value of a call to [enter].
    */
  -dynamic leave(scope) {
  +void leave(scope) {
     if (wtfEnabled) {
       _arg1[0] = scope;
       _leaveScope.apply(_arg1, thisArg: _trace);
  
positive.code: /**
   * Create trace scope. Scopes must be strictly nested and are analogous to stack frames, but
   * do not have to follow the stack frames. Instead it is recommended that they follow logical
   * nesting.
   */
  dynamic createScope(String signature, [flags]) {
    if (wtfEnabled) {
  
negative.code: 
  /**
   * Used to mark Async start. Async are similar to scope but they don't have to be strictly nested.
   * The return value is used in the call to [endAsync]. Async ranges only work if WTF has been enabled.
   *
   *     someMethod() {
   *        var s = startAsync('HTTP:GET', 'some.url');
  