:info prints kinds in closed type family equations without enabling -fprint-explicit-kinds

Load this file into GHCi:

{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeFamilies #-}
module Bug where

type family Foo (a :: k) :: k where
  Foo a = a

And run :info on Foo:

$ /opt/ghc/8.4.3/bin/ghci Bug.hs
GHCi, version 8.4.3: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/ryanglscott/.ghci
[1 of 1] Compiling Bug              ( Bug.hs, interpreted )
Ok, one module loaded.
λ> :i Foo
type family Foo (a :: k) :: k
  where Foo k a = a
        -- Defined at Bug.hs:5:1

Note that when printing the equation for Foo, the kind k is treated as though it were the first visible argument to Foo, even though -fprint-explicit-kinds is not enabled. This is because ppr_tc_args in IfaceType does not take -fprint-explicit-kinds into account.

Patch incoming (pending a ./validate).

Trac metadata

Trac field	Value
Version	8.4.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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