anchor.diff:  ///
   /// Typically used as the outline of a 'host' widget to make a notch that
   /// accommodates a 'guest' widget. e.g the [BottomAppBar] may have a notch to
  -/// accomodate the [FloatingActionBar].
  +/// accommodate the [FloatingActionButton].
   
   /// See also: [ShapeBorder], which defines a shaped border without a dynamic
   /// notch.
  
positive.code: import 'dart:math' as math;
  
  import 'basic_types.dart';
  
negative.code:   /// `host` is the bounding box for the returned shape. Conceptually this is
    /// the rectangle to which the notch will be applied.
    ///
    /// `guest` is the bounding box of a circle that the notch accommodates. All
    /// points in the circle bounded by `guest` will be outside of the returned
    /// path.
    ///
  