anchor.diff:  external T unsafeCast<T>(dynamic value);
   
   // Powers of 10 up to 10^22 are representable as doubles.
  -// Powers of 10 above that are only approximate due to lack of precission.
  +// Powers of 10 above that are only approximate due to lack of precision.
   // Used by double-parsing.
   const POWERS_OF_TEN = const [
     1.0, // 0
  
positive.code:   return digit1 * 16 + digit2 - (digit2 & 256);
  }
  
  /// A resusable `null`-valued future used by `dart:async`.
  ///
  /// **DO NOT USE.**
  ///
  
negative.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 heterogeneous
  /// list is really a value of the surrounding map).
  ///
  /// Must only be used for casts which would definitely *succeed*
  