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, 4 insertions, 2 deletions

diff --git a/libraries/base/Debug/Trace.hs b/libraries/base/Debug/Trace.hs
index 92e5b205c8..9705e29fdc 100644
--- a/libraries/base/Debug/Trace.hs
+++ b/libraries/base/Debug/Trace.hs
@@ -1,5 +1,7 @@
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE UnboxedTuples #-}
 {-# LANGUAGE Unsafe #-}
-{-# LANGUAGE MagicHash, UnboxedTuples #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -42,7 +44,6 @@ module Debug.Trace (
         traceMarkerIO,
   ) where
 
-import Prelude
 import System.IO.Unsafe
 import Control.Monad
 
@@ -51,6 +52,7 @@ import GHC.Base
 import qualified GHC.Foreign
 import GHC.IO.Encoding
 import GHC.Ptr
+import GHC.Show
 import GHC.Stack
 import Data.List