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{-# LANGUAGE Haskell2010 #-}
{-# OPTIONS_GHC -ddump-types -dsuppress-module-prefixes #-}
{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleContexts #-}
-- See #1456
-- The key thing here is that foo should get the type
-- foo :: forall s b chain. (Zork s (Z [Char]) b)
-- => Q s (Z [Char]) chain -> ST s ()
-- Note the quantification over 'b', which was previously
-- omitted; see Note [Important subtlety in oclose] in GHC.Tc.Instance.FunDeps
-- (Note removed in ecddaca17dccbe1d0b56220d838fce8bc4b97884, but you can
-- find it in the history)
-- June 2021: marking this test as should_fail again.
-- See https://gitlab.haskell.org/ghc/ghc/-/issues/20064
module ShouldCompile where
import GHC.ST
data Q s a chain = Node s a chain
data Z a = Z a
s :: Q s (Z [Char]) chain -> Q s (Z [Char]) chain
s = undefined
class Zork s a b | a -> b where
huh :: Q s a chain -> ST s ()
--foo :: Zork s (Z [Char]) b => Q s (Z [Char]) chain -> ST s ()
foo b = huh (s b)
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