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|
{-# LANGUAGE AllowAmbiguousTypes
, FunctionalDependencies
, KindSignatures
, MultiParamTypeClasses
, PolyKinds
#-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.Records
-- Copyright : (c) Adam Gundry 2015-2016
-- License : see libraries/base/LICENSE
--
-- Maintainer : cvs-ghc@haskell.org
-- Stability : internal
-- Portability : non-portable (GHC extensions)
--
-- This module defines the 'HasField' class used by the
-- @OverloadedRecordFields@ extension. See the
-- <https://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields
-- wiki page> for more details.
--
-----------------------------------------------------------------------------
module GHC.Records
( HasField(..)
) where
-- | Constraint representing the fact that the field @x@ belongs to
-- the record type @r@ and has field type @a@. This will be solved
-- automatically, but manual instances may be provided as well.
class HasField (x :: k) r a | x r -> a where
-- | Selector function to extract the field from the record.
getField :: r -> a
|
