Re: [GHC] #14607: Core Lint error

22 Dec 2017

      #14607: Core Lint error
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  TypeInType,
                                     |  DeferredTypeErrors
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14605 #14584     |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by Iceland_jack:

Old description:
...
This produces long {{{#!hs
{-# Language DerivingStrategies #-}
{-# Language GADTs #-}
{-# Language GeneralizedNewtypeDeriving #-}
{-# Language InstanceSigs #-}
{-# Language KindSignatures #-}
{-# Language TypeFamilies #-}
{-# Language TypeInType #-}
{-# Language TypeOperators #-}
import Data.Kind
data DEFUNC :: Type -> Type -> Type where
  (:~>) :: a -> b -> DEFUNC a b
type a ~> b = DEFUNC a b -> Type
data LamCons a :: Type ~> Type where
  LamCons :: a -> LamCons a ([a] :~> [a])
class Mk (app :: Type ~> Type) where
  type Arg app :: Type
mk :: Arg app -> app (a :~> b)
instance Mk (LamCons a :: Type ~> Type) where
  type Arg (LamCons a) = a
mk :: a -> LamCons (a :~> b)
  mk = LamCons
}}}
erros with `ghci -ignore-dot-ghci -fdefer-type-errors -dcore-lint bug.hs`
on GHC 8.2.1 and 8.3.20171208.
New description:

 This produces a long Core lint error:

 {{{#!hs
 {-# Language DerivingStrategies #-}
 {-# Language GADTs #-}
 {-# Language GeneralizedNewtypeDeriving #-}
 {-# Language InstanceSigs #-}
 {-# Language KindSignatures #-}
 {-# Language TypeFamilies #-}
 {-# Language TypeInType #-}
 {-# Language TypeOperators #-}

 import Data.Kind

 data DEFUNC :: Type -> Type -> Type where
   (:~>) :: a -> b -> DEFUNC a b

 type a ~> b = DEFUNC a b -> Type

 data LamCons a :: Type ~> Type where
   LamCons :: a -> LamCons a ([a] :~> [a])

 class Mk (app :: Type ~> Type) where
   type Arg app :: Type

   mk :: Arg app -> app (a :~> b)

 instance Mk (LamCons a :: Type ~> Type) where
   type Arg (LamCons a) = a

   mk :: a -> LamCons (a :~> b)
   mk = LamCons
 }}}

 with `ghci -ignore-dot-ghci -fdefer-type-errors -dcore-lint bug.hs` on GHC
 8.2.1 and 8.3.20171208.

--

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14607#comment:1
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