Core lint error with defer-typed-holes

Another Core Lint error

{-# Options_GHC -dcore-lint -fdefer-typed-holes #-}

{-# Language ViewPatterns, PatternSynonyms, GeneralizedNewtypeDeriving, DeriveTraversable #-}

import Data.Bifunctor.Fix
import Data.Bifunctor.Tannen
import Test.QuickCheck
import Test.QuickCheck.Function
import Control.Applicative

newtype ZL a = ZL { getZL :: Fix (Tannen Maybe (,)) a }
  deriving (Eq, Ord, Read, Show, Functor, Applicative, Foldable, Traversable)

fromList :: [a] -> ZL a
fromList []     = Nil
fromList (x:xs) = x:::fromList xs

pattern Nil :: ZL a
pattern Nil = ZL (In (Tannen Nothing))

foo :: ZL a -> Maybe (a, ZL a)
foo (ZL (In (Tannen (Just (as, a))))) = Just (a, ZL as)

infixr 5 :::
pattern (:::) :: a -> ZL a -> ZL a
pattern a:::as   <- ZL (In (Tannen (Just (ZL -> as, a))))
  where a:::ZL as = ZL (In (Tannen (Just (as, a))))

u (Fn f) as bs = let
  (xs, ys) = (ZipList as, ZipList bs)

  in getZipList (liftA2 f xs ys) == toList (liftA2 f (fromList as) (fromList bs))

unfortunately I don't have time to reduce it

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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