[commit: ghc] wip/ttypeable: Note need for mkTrApp (ac91bb2)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/ttypeable
Link       : http://ghc.haskell.org/trac/ghc/changeset/ac91bb2c216df2d1fdc52f6b3c640cffd992c9bf/ghc

>---------------------------------------------------------------

commit ac91bb2c216df2d1fdc52f6b3c640cffd992c9bf
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Fri Jul 8 23:10:45 2016 +0200

    Note need for mkTrApp


>---------------------------------------------------------------

ac91bb2c216df2d1fdc52f6b3c640cffd992c9bf
 libraries/base/Data/Typeable/Internal.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libraries/base/Data/Typeable/Internal.hs b/libraries/base/Data/Typeable/Internal.hs
index 9e22c22..25c7399 100644
--- a/libraries/base/Data/Typeable/Internal.hs
+++ b/libraries/base/Data/Typeable/Internal.hs
@@ -225,7 +225,9 @@ mkTrCon tc kind = TrTyCon fpr tc kind
     fpr    = fingerprintFingerprints [fpr_tc, fpr_k]
 
 -- | Construct a representation for a type application.
--- TODO: Is this necessary?
+--
+-- Note that this is known-key to the compiler, which uses it in desugar
+-- 'Typeable' evidence.
 mkTrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1).
            TypeRep (a :: k1 -> k2)
         -> TypeRep (b :: k1)