weeder-2.7.0: test/Spec/ApplicativeDo/ApplicativeDo.hs

{-# LANGUAGE ApplicativeDo #-}
module Spec.ApplicativeDo.ApplicativeDo where

newtype Foo a = Foo a

instance Functor Foo where
  fmap f (Foo a) = Foo (f a)

instance Applicative Foo where
  pure = Foo
  Foo f <*> Foo a = Foo (f a)

root :: Foo Int
root = do
  a <- Foo 1
  b <- Foo 2
  pure (a + b)