    {-# LANGUAGE Trustworthy #-}
    {-# LANGUAGE NoImplicitPrelude
               , RankNTypes
               , ExistentialQuantification
      #-}
    {-# OPTIONS_HADDOCK not-home #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.Desugar
    -- Copyright   :  (c) The University of Glasgow, 2007
    -- License     :  see libraries/base/LICENSE
    --
    -- Maintainer  :  cvs-ghc@haskell.org
    -- Stability   :  internal
    -- Portability :  non-portable (GHC extensions)
    --
    -- Support code for desugaring in GHC
    --
    -----------------------------------------------------------------------------

    module GHC.Desugar ((>>>), AnnotationWrapper(..), toAnnotationWrapper) where

    import Control.Arrow    (Arrow(..))
    import Control.Category ((.))
    import Data.Data        (Data)

    -- A version of Control.Category.>>> overloaded on Arrow
    (>>>) :: forall arr. Arrow arr => forall a b c. arr a b -> arr b c -> arr a c
    -- NB: the type of this function is the "shape" that GHC expects
    --     in tcInstClassOp.  So don't put all the foralls at the front!
    --     Yes, this is a bit grotesque, but heck it works and the whole
    --     arrows stuff needs reworking anyway!
    arr a b
    f >>> :: forall (arr :: * -> * -> *) a b c.
    Arrow arr =>
    arr a b -> arr b c -> arr a c
    >>> arr b c
    g = arr b c
    g arr b c -> arr a b -> arr a c
    forall b c a. arr b c -> arr a b -> arr a c
    forall {k} (cat :: k -> k -> *) (b :: k) (c :: k) (a :: k).
    Category cat =>
    cat b c -> cat a b -> cat a c
    . arr a b
    f
    {-# INLINE (>>>) #-} -- see Note [INLINE on >>>] in Control.Category

    -- A wrapper data type that lets the typechecker get at the appropriate dictionaries for an annotation
    data AnnotationWrapper = forall a. (Data a) => AnnotationWrapper a

    toAnnotationWrapper :: (Data a) => a -> AnnotationWrapper
    toAnnotationWrapper :: forall a. Data a => a -> AnnotationWrapper
    toAnnotationWrapper a
    what = a -> AnnotationWrapper
    forall a. Data a => a -> AnnotationWrapper
    AnnotationWrapper a
    what