Understanding the Effect Monad. Erroneous example

[JohnGurin]

Section:
  Hello-World

Issue Type:
  Bug

Folder/File(s):
  - Hello-World/Effect-and-Aff/src/Effect/Native-Side-Effects-via-Effect.md

data Unit = Unit
unit :: Unit
unit = Unit

type PendingComputation a = (Unit -> a)
data Effect a = Box (PendingComputation a -> a)

unsafePerformEffect :: {- forall a. -} Effect a -> a
unsafePerformEffect (Box pendingComputation) = pendingComputation unit
--                                                                ^^^^
{-
 Could not match type

    Unit

  with type

    Unit -> a0
-}

source

try.purescript.org

As a suggestion

import Prelude

unsafePerformEffect :: forall a. Semiring a => Effect a -> a
unsafePerformEffect (Box pendingComputation) = pendingComputation (\_ -> one)

[JordanMartinez]

The issue is here:

type PendingComputation a = (Unit -> a)
 -- expands to    Box (Unit -> a -> a)
-data Effect a = Box (PendingComputation a -> a)
 -- expands to    Box (Unit -> a)
+data Effect a = Box (PendingComputation a)