#14578: Incorrect parenthesization of types in -ddump-deriv -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: deriving Operating System: Unknown/Multiple | Architecture: Type of failure: Debugging | Unknown/Multiple information is incorrect | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by RyanGlScott: Old description:
Compiling this program on GHC 8.2 or later:
{{{#!hs {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# OPTIONS_GHC -ddump-deriv #-} module Bug where
import Control.Applicative import Data.Functor.Compose import Data.Semigroup
newtype App f a = MkApp (f a) deriving (Functor, Applicative)
instance (Applicative f, Semigroup a) => Semigroup (App f a) where (<>) = liftA2 (<>)
newtype Wat f g a = MkWat (App (Compose f g) a) deriving Semigroup }}}
Will result in some incorrectly pretty-printed types in the `-ddump- deriv` output:
{{{ $ /opt/ghc/8.2.2/bin/ghci Bug.hs -dsuppress-uniques GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted )
==================== Derived instances ==================== Derived class instances:
<elided for brevity>
instance (Data.Semigroup.Semigroup a, GHC.Base.Applicative g, GHC.Base.Applicative f) => Data.Semigroup.Semigroup (Bug.Wat f g a) where (Data.Semigroup.<>) = GHC.Prim.coerce @(Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(Bug.Wat f g a -> Bug.Wat f g a -> Bug.Wat f g a) (Data.Semigroup.<>) Data.Semigroup.sconcat = GHC.Prim.coerce @(Data.List.NonEmpty.NonEmpty Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(Data.List.NonEmpty.NonEmpty Bug.Wat f g a -> Bug.Wat f g a) Data.Semigroup.sconcat Data.Semigroup.stimes = GHC.Prim.coerce @(forall (b :: TYPE GHC.Types.LiftedRep). GHC.Real.Integral b => b -> Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(forall (b :: TYPE GHC.Types.LiftedRep). GHC.Real.Integral b => b -> Bug.Wat f g a -> Bug.Wat f g a) Data.Semigroup.stimes }}}
Notice that is shows `Bug.App Data.Functor.Compose.Compose f g a`, which is wrong. It should be `Bug.App (Data.Functor.Compose.Compose f g) a`.
New description: Compiling this program on GHC 8.2 or later: {{{#!hs {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# OPTIONS_GHC -ddump-deriv #-} module Bug where import Control.Applicative import Data.Functor.Compose import Data.Semigroup newtype App f a = MkApp (f a) deriving (Functor, Applicative) instance (Applicative f, Semigroup a) => Semigroup (App f a) where (<>) = liftA2 (<>) newtype Wat f g a = MkWat (App (Compose f g) a) deriving Semigroup }}} Will result in some incorrectly pretty-printed types in the `-ddump-deriv` output: {{{ $ /opt/ghc/8.2.2/bin/ghci Bug.hs -dsuppress-uniques GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) ==================== Derived instances ==================== Derived class instances: <elided for brevity> instance (Data.Semigroup.Semigroup a, GHC.Base.Applicative g, GHC.Base.Applicative f) => Data.Semigroup.Semigroup (Bug.Wat f g a) where (Data.Semigroup.<>) = GHC.Prim.coerce @(Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(Bug.Wat f g a -> Bug.Wat f g a -> Bug.Wat f g a) (Data.Semigroup.<>) Data.Semigroup.sconcat = GHC.Prim.coerce @(Data.List.NonEmpty.NonEmpty Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(Data.List.NonEmpty.NonEmpty Bug.Wat f g a -> Bug.Wat f g a) Data.Semigroup.sconcat Data.Semigroup.stimes = GHC.Prim.coerce @(forall (b :: TYPE GHC.Types.LiftedRep). GHC.Real.Integral b => b -> Bug.App Data.Functor.Compose.Compose f g a -> Bug.App Data.Functor.Compose.Compose f g a) @(forall (b :: TYPE GHC.Types.LiftedRep). GHC.Real.Integral b => b -> Bug.Wat f g a -> Bug.Wat f g a) Data.Semigroup.stimes }}} Notice that it shows `Bug.App Data.Functor.Compose.Compose f g a` within the visible type applications, which is wrong. It should be `Bug.App (Data.Functor.Compose.Compose f g) a`. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14578#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler