shape property Null safety
The shape cannot be interpolated; animating between two BoxDecorations with different shapes will result in a discontinuity in the rendering. To interpolate between two shapes, consider using ShapeDecoration and different ShapeBorders; in particular, CircleBorder instead of BoxShape.circle and RoundedRectangleBorder instead of BoxShape.rectangle.
The shape or the borderRadius won't clip the children of the decorated Container. If the clip is required, insert a clip widget (e.g., ClipRect, ClipRRect, ClipPath) as the child of the Container. Be aware that clipping may be costly in terms of performance.
final BoxShape shape;