Flutter decorators using callables

main.dart

class Key {}
class Size {}
class Widget {}

// Decorator uses Dart callable magic
// https://dart.dev/language/callable-objects
class SizedBoxDecorator {
  SizedBoxDecorator(this.child);
 
  final Widget child;
  
  Widget call({
    Key? key,
    double? width,
    double? height,
  }) => Widget();
  
  Widget expand({Key? key}) => Widget();
  Widget fromSize({Key? key, Size? size}) => Widget();
  Widget shrink({Key? key}) => Widget();
  Widget square({Key? key, double? dimension}) => Widget();
}

extension BasicDecorators on Widget {
  // Gross allocation :(
  SizedBoxDecorator get sizedBox => SizedBoxDecorator(this);
}

void main() {
  Widget()
    .sizedBox.square(dimension: 50)
    .sizedBox.shrink()
    .sizedBox.fromSize(size: Size())
    .sizedBox.expand()
    .sizedBox(width: 100, height: 100);
}