Export `Traversable()` and `Foldable()` from Prelude

This exposes *only* the type-classes w/o any of their methods.
This is the very first step for implementing BPP (see #9586), which
already requires breaking up several import-cycles leading back to `Prelude`.

Ideally, importing `Prelude` should be avoided in most `base` modules,
as `Prelude` does not define any entities, but rather re-exports
existing ones.

Test Plan: validate passes

Reviewers: ekmett, austin

Reviewed By: ekmett, austin

Subscribers: simonmar, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D209

GHC Trac Issues: #9586

1 files changed, 3 insertions, 3 deletions

diff --git a/libraries/base/GHC/Exts.hs b/libraries/base/GHC/Exts.hs
index 938631001a..6499da878a 100755
--- a/libraries/base/GHC/Exts.hs
+++ b/libraries/base/GHC/Exts.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE Unsafe #-}
 {-# LANGUAGE MagicHash, UnboxedTuples, AutoDeriveTypeable, TypeFamilies, MultiParamTypeClasses, FlexibleInstances #-}
+{-# LANGUAGE NoImplicitPrelude #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -71,14 +72,13 @@ module GHC.Exts
         IsList(..)
        ) where
 
-import Prelude
-
-import GHC.Prim hiding (coerce)
+import GHC.Prim hiding (coerce, Constraint)
 import GHC.Base hiding (coerce) -- implicitly comes from GHC.Prim
 import GHC.Word
 import GHC.Int
 import GHC.Ptr
 import GHC.Stack
+
 import qualified Data.Coerce
 import Data.String
 import Data.List