anchor.diff:  /// If applied to a class method, or parameter of such,
   /// any method implementing that interface method is also annotated.
   /// If multiple `Since` annotations apply to the same declaration or
  -/// parameter, the latest version takes precendence.
  +/// parameter, the latest version takes precedence.
   ///
   /// Any use of a marked API may trigger a warning if the using code
   /// does not require an SDK version guaranteeing that the API is available,
  
positive.code: /// Can be used internally in platform library implementations of
  /// data structures, where a value is known to have a type different
  /// from its static type (like knowing that a string is definitely
  /// a "_OneByteString" or that the value stored into a heterogenous
  /// list is really a value of the surrounding map).
  ///
  /// Must only be used for casts which would definitely *succeed*
  
negative.code:   return digit1 * 16 + digit2 - (digit2 & 256);
  }
  
  /// A reusable `null`-valued future used by `dart:async`.
  ///
  /// **DO NOT USE.**
  ///
  