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|
{-# LANGUAGE
ScopedTypeVariables
, DataKinds
, GADTs
, RankNTypes
, TypeOperators
, PolyKinds -- Comment out PolyKinds and the bug goes away.
#-}
{-# OPTIONS_GHC -O #-}
-- The bug is in GHC.Core.Op.Simplify.Utils.abstractFloats, so we need -O to trigger it
module KeyValue where
import Data.Kind
data AccValidation err a = AccFailure err | AccSuccess a
data KeyValueError = MissingValue
type WithKeyValueError = AccValidation [KeyValueError]
missing :: forall f rs. RecApplicative rs => Rec (WithKeyValueError :. f) rs
missing = rpure missingField
where
missingField :: forall x. (WithKeyValueError :. f) x
missingField = Compose $ AccFailure [MissingValue]
data Rec :: (u -> Type) -> [u] -> Type where
RNil :: Rec f '[]
(:&) :: !(f r) -> !(Rec f rs) -> Rec f (r ': rs)
newtype Compose (f :: l -> Type) (g :: k -> l) (x :: k)
= Compose { getCompose :: f (g x) }
type (:.) f g = Compose f g
class RecApplicative rs where
rpure
:: (forall x. f x)
-> Rec f rs
|
