SVG

Error

 • Couldn't match type ‘Circle’ with ‘Line’
      Expected type: Tree Line
        Actual type: Tree Circle
    • In the expression: Node (Circle (20, 30) 50) []
      In the second argument of ‘Node’, namely
        ‘[Node (Circle (20, 30) 50) []]’
      In the expression:
        Node (Line (100, 100) (30, 60)) [Node (Circle (20, 30) 50) []]
   |
11 | sampleTree = Node (Line (100,100) (30,60)) [Node (Circle (20,30) 50) []]
   |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^

svg.hs

class SvgNode a where
  toSVG :: a -> String
  element :: a -> String
  
instance SvgNode Circle where
  toSVG (Circle (x,y) radius) = "<circle cx='" ++ show x ++ "' cy='" ++ show y ++ "' r='" ++ show radius ++ "' stroke='red' fill='transparent' stroke-width='5'>"
  element _ = "circle"
  
  
  
instance SvgNode Rectangle where
  toSVG (Rectangle (x,y) width height) = "<rect x='" ++ show x ++ "' y='" ++ show y ++ "' width='" ++ show width ++ "' height='" ++ show height ++ "' stroke='black' fill='transparent' stroke-width='5'>"
  element _ = "rectangle"

-- this is where I get the issue. I want to create a tree of SVGNode with both Line & Circle
sampleTree :: forall a. SvgNode a => Tree a
sampleTree = Node (Line (100,100) (30,60)) [Node (Circle (20,30) 50) []]

Tree.hs

data Tree a = Empty | Node a [Tree a]