module FizzBuzz where

data StringInt a = Int a | String a

handleRule:: StringInt a -> a
handleRule x
    | x % 3 == 0 = StringInt "Fizz"
    | x % 5 == 0 = StringInt "Buzz"
    | otherwise = x

run:: [StringInt a] -> [a]
run = map handleRule

module FizzBuzzSpec (spec) where

    import Test.Hspec
    import FizzBuzz

    spec :: Spec
    spec = describe "FizzBuzz#run" $ do
        it "should have displayed Fizz for number 3" $
            run [1..10]:2 `shouldBe` "Fizz"
        it "should have displayed Buzz for number 5" $
            run [1..10]:4 `shouldBe` "Buzz"

• Occurs check: cannot construct the infinite type: a ~ StringInt a
• In the expression: x
  In an equation for ‘handleRule’:
      handleRule x
        | (%) x 3 == 0 = StringInt "Fizz"
        | (%) x 5 == 0 = StringInt "Buzz"
        | otherwise = x
• Relevant bindings include
    x :: StringInt a (bound at src/FizzBuzz.hs:6:12)
    handleRule :: StringInt a -> a (bound at src/FizzBuzz.hs:6:1)