anchor.diff:         assert(onError != null),
          assert(brightness != null);
   
  +  /// Create a ColorScheme based on a purple primary color that matches the
  +  /// [baseline Material color scheme](https://material.io/design/color/the-color-system.html#color-theme-creation).
     const ColorScheme.light({
       this.primary = const Color(0xff6200ee),
       this.primaryVariant = const Color(0xff3700b3),
  
positive.code: /// with [ColorScheme.fromSwatch].
  @immutable
  class ColorScheme extends Diagnosticable {
    const ColorScheme({
      @required this.primary,
      @required this.primaryVariant,
  
negative.code:     );
    }
  
    /// Linearly interpolate between two [ColorScheme] objects.
    ///
    /// {@macro flutter.material.themeData.lerp}
    static ColorScheme lerp(ColorScheme a, ColorScheme b, double t) {
      return ColorScheme(
        primary: Color.lerp(a.primary, b.primary, t),
  