Core lint error from PartialTypeSignatures

{-# Language PartialTypeSignatures #-}
{-# Language PolyKinds             #-}
{-# Language ScopedTypeVariables   #-}

{-# Options_GHC -dcore-lint #-}

top :: forall f. _
top = undefined where

  x :: forall a. f a
  x = undefined

causes Core lint errors:

$ ~/../inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci 922_bug.hs
GHCi, version 8.7.20181230: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( 922_bug.hs, interpreted )
*** Core Lint errors : in result of Desugar (before optimization) ***
<no location info>: warning:
    In the type ‘forall (f :: k_a1z6 -> *) w. w’
    @ k_a1z6 is out of scope
*** Offending Program ***
Rec {
$trModule :: Module
[LclIdX]
$trModule = Module (TrNameS "main"#) (TrNameS "Main"#)

top :: forall (f :: k_a1z6 -> *) w. w
[LclIdX]
top
  = \ (@ (f_a2BY :: k_a1z6 -> *)) (@ w_a2BZ) ->
      (\ (@ k_a1z6) (@ (f_a1yV :: k_a1z6 -> *)) (@ w_a1yN) ->
         let {
           $dIP_a2BO :: ?callStack::CallStack
           [LclId]
           $dIP_a2BO
             = emptyCallStack
               `cast` (Sym (N:IP[0] <"callStack">_N <CallStack>_N)
                       :: CallStack ~R# (?callStack::CallStack)) } in
         let {
           $dIP_a2BD :: HasCallStack
           [LclId]
           $dIP_a2BD
             = (pushCallStack
                  (unpackCString# "undefined"#,
                   SrcLoc
                     (unpackCString# "main"#)
                     (unpackCString# "Main"#)
                     (unpackCString# "922_bug.hs"#)
                     (I# 8#)
                     (I# 7#)
                     (I# 8#)
                     (I# 16#))
                  ($dIP_a2BO
                   `cast` (N:IP[0] <"callStack">_N <CallStack>_N
                           :: (?callStack::CallStack) ~R# CallStack)))
               `cast` (Sym (N:IP[0] <"callStack">_N <CallStack>_N)
                       :: CallStack ~R# (?callStack::CallStack)) } in
         letrec {
           top_a1yW :: w_a1yN
           [LclId]
           top_a1yW
             = letrec {
                 x_a1yv :: forall (a :: k_a1z6). f_a1yV a
                 [LclId]
                 x_a1yv
                   = \ (@ (a_a1zd :: k_a1z6)) ->
                       let {
                         $dIP_a2BP :: ?callStack::CallStack
                         [LclId]
                         $dIP_a2BP
                           = emptyCallStack
                             `cast` (Sym (N:IP[0] <"callStack">_N <CallStack>_N)
                                     :: CallStack ~R# (?callStack::CallStack)) } in
                       let {
                         $dIP_a2Bz :: HasCallStack
                         [LclId]
                         $dIP_a2Bz
                           = (pushCallStack
                                (unpackCString# "undefined"#,
                                 SrcLoc
                                   (unpackCString# "main"#)
                                   (unpackCString# "Main"#)
                                   (unpackCString# "922_bug.hs"#)
                                   (I# 11#)
                                   (I# 7#)
                                   (I# 11#)
                                   (I# 16#))
                                ($dIP_a2BP
                                 `cast` (N:IP[0] <"callStack">_N <CallStack>_N
                                         :: (?callStack::CallStack) ~R# CallStack)))
                             `cast` (Sym (N:IP[0] <"callStack">_N <CallStack>_N)
                                     :: CallStack ~R# (?callStack::CallStack)) } in
                       break<0>() undefined @ 'LiftedRep @ (f_a1yV a_a1zd) $dIP_a2Bz; } in
               break<1>() undefined @ 'LiftedRep @ w_a1yN $dIP_a2BD; } in
         top_a1yW)
        @ Any @ Any @ w_a2BZ
end Rec }

*** End of Offense ***


<no location info>: error:
Compilation had errors


*** Exception: ExitFailure 1
>

Trac metadata

Trac field	Value
Version	8.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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