Open-closed principle violation example

main.dart

sealed class Shape {}

class Circle extends Shape {
 Circle(this.radius);

 final double radius;
}

class Rectangle extends Shape {
 Rectangle(this.width, this.height);
    
    final double width;
    final double height;
}

class SquareCalculator {
 double calcSquare(Shape shape) {
  if (shape is Circle) {
       return 3.14 * shape.radius * shape.radius;
    }
    if (shape is Rectangle) {
       return shape.width * shape.height;
    }
    throw 'Unrecognized Shape';
 }
}

void main() {
 final calculator = SquareCalculator();
    
    final circle = Circle(25);
    
    // prints 1962,5
    print(calculator.calcSquare(circle)); 
    
    final rectangle = Rectangle(10, 20);
    
    /// prints 200
    print(calculator.calcSquare(rectangle));
}