anchor.diff:    /**
      * Checks whether [actual] is null.
      */
  -  @deprecated
     static void isNull(actual, [String reason = null]) {
       if (null == actual) return;
       String msg = _getMessage(reason);
  
positive.code:   /**
     * Checks whether the actual value is a bool and its value is false.
     */
    @deprecated
    static void isFalse(var actual, [String reason = null]) {
      if (_identical(actual, false)) return;
      String msg = _getMessage(reason);
  
negative.code:    * Specialized equality test for strings. When the strings don't match,
     * this method shows where the mismatch starts and ends.
     */
    static void stringEquals(String expected,
                             String actual,
                             [String reason = null]) {
  