SOLID: Open-Closed Principle `bad`

badImplShapes.go

package main

import (
	"fmt"
	"math"
)

type badRect struct {
	Width, Height float64
}

type badCircle struct {
	Radius float64
}

// Must be changed for every new struct.
func badMeasureArea(i any) {
	fmt.Println("calculating area for: ")
	switch i.(type) {
	case badRect:
		r := i.(badRect)
		fmt.Println("Rectangle")
		fmt.Println(r.Width * r.Height)
	case badCircle:
		c := i.(badCircle)
		fmt.Println("Circle")
		fmt.Println(math.Pi * c.Radius * c.Radius)
	}
	fmt.Println()
}

// ---
func main() {
	r := badRect{Width: 3, Height: 4}
	c := badCircle{Radius: 5}

	badMeasureArea(r)
	badMeasureArea(c)
}