anchor.diff:          b.darkColor,
           b.textColor,
           b.style,
  +        b.margin * t,
           b._position,
           b._opacity * t.clamp(0.0, 1.0),
  -        b.margin * t,
         );
       }
       if (b == null) {
  
positive.code:   // set the internal _position property.
    final FlutterLogoStyle style;
  
    // The following are set when lerping, to represent states that can't be
    // represented by the constructor.
    final double _position; // -1.0 for stacked, 1.0 for horizontal, 0.0 for no logo
    final double _opacity; // 0.0 .. 1.0
  
    /// How far to inset the logo from the edge of the container.
    final EdgeInsets margin;
  
    bool get _inTransition => _opacity != 1.0 || (_position != -1.0 && _position != 0.0 && _position != 1.0);
  
  
negative.code:   /// controls whether and where to draw the "Flutter" label. If one is shown,
    /// the [textColor] controls the color of the label.
    ///
    /// The [lightColor], [darkColor], [textColor], [style], and [margin]
    /// arguments must not be null.
    const FlutterLogoDecoration({
      this.lightColor: const Color(0xFF42A5F5), // Colors.blue[400]
      this.darkColor: const Color(0xFF0D47A1), // Colors.blue[900]
      this.textColor: const Color(0xFF616161),
      this.style: FlutterLogoStyle.markOnly,
      this.margin: EdgeInsets.zero,
    }) : assert(lightColor != null),
         assert(darkColor != null),
         assert(textColor != null),
         assert(style != null),
         assert(margin != null),
         _position = style == FlutterLogoStyle.markOnly ? 0.0 : style == FlutterLogoStyle.horizontal ? 1.0 : -1.0, // ignore: CONST_EVAL_TYPE_BOOL_NUM_STRING
         // (see https://github.com/dart-lang/sdk/issues/26980 for details about that ignore statement)
         _opacity = 1.0;
  
    const FlutterLogoDecoration._(this.lightColor, this.darkColor, this.textColor, this.style, this.margin, this._position, this._opacity);
  
    /// The lighter of the two colors used to paint the logo.
    ///
  