make QSem and QSemN newtypes

Reviewers: RyanGlScott, ekmett, hvr, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, carter

GHC Trac Issues: #15995

Differential Revision: https://phabricator.haskell.org/D5456

libraries/base/Control/Concurrent/QSem.hs

 {-# LANGUAGE Safe #-}
 {-# LANGUAGE BangPatterns #-}
-{-# OPTIONS_GHC -funbox-strict-fields #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -39,7 +38,7 @@ import Data.Maybe
 --
 -- is safe; it never loses a unit of the resource.
 --
-data QSem = QSem !(MVar (Int, [MVar ()], [MVar ()]))
+newtype QSem = QSem (MVar (Int, [MVar ()], [MVar ()]))
 
 -- The semaphore state (i, xs, ys):
 --

libraries/base/Control/Concurrent/QSemN.hs

 {-# LANGUAGE Safe #-}
-{-# LANGUAGE BangPatterns #-}
-{-# OPTIONS_GHC -funbox-strict-fields #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -41,7 +39,7 @@ import Data.Maybe
 --
 -- is safe; it never loses any of the resource.
 --
-data QSemN = QSemN !(MVar (Int, [(Int, MVar ())], [(Int, MVar ())]))
+newtype QSemN = QSemN (MVar (Int, [(Int, MVar ())], [(Int, MVar ())]))
 
 -- The semaphore state (i, xs, ys):
 --