This patch is taken from upstream.  It fixes a test to work with GHC 8.6.
The paths have been slightly altered to work with the release tarball.

See <https://github.com/simonmar/monad-par/issues/66>.

From e20f81c8060208e4fb038e8f0e0668b41d72a6fb Mon Sep 17 00:00:00 2001
From: Clint Adams <clint@debian.org>
Date: Sat, 31 Aug 2019 14:12:34 -0400
Subject: [PATCH] Use a case statement instead of pattern-matching in
 case_test_diamond

This avoids the need for a MonadFail instance.  Closes #66
---
 monad-par/tests/ParTests_shared.hs | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tests/ParTests_shared.hs b/tests/ParTests_shared.hs
index 31f438d..b2de50c 100644
--- a/tests/ParTests_shared.hs
+++ b/tests/ParTests_shared.hs
@@ -109,12 +109,15 @@ case_test_diamond :: Assertion
 case_test_diamond = 9 @=? (m :: Int)
  where 
   m = runPar $ do
-      [a,b,c,d] <- sequence [new,new,new,new]
-      fork $ do x <- get a; put b (x+1)
-      fork $ do x <- get a; put c (x+2)
-      fork $ do x <- get b; y <- get c; put d (x+y)
-      fork $ do put a 3
-      get d
+      abcd <- sequence [new,new,new,new]
+      case abcd of
+          [a,b,c,d] -> do
+              fork $ do x <- get a; put b (x+1)
+              fork $ do x <- get a; put c (x+2)
+              fork $ do x <- get b; y <- get c; put d (x+y)
+              fork $ do put a 3
+              get d
+          _ -> error "Oops"
 
 -- | Violate IVar single-assignment:
 --
-- 
2.23.0

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<div class='path'>path: <a href='/guix/log/?id=8fc6059b024a42f73cc0203ce62a7baf0d64763c'>root</a>/<a href='/guix/log/etc?id=8fc6059b024a42f73cc0203ce62a7baf0d64763c'>etc</a>/<a href='/guix/log/etc/guix-publish.conf.in?id=8fc6059b024a42f73cc0203ce62a7baf0d64763c'>guix-publish.conf.in</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/guix-publish.conf.in?id=8fc6059b024a42f73cc0203ce62a7baf0d64763c&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-11-23 15:42:01 +0100'>2018-11-23</span></td><td><a href='/guix/commit/etc/guix-publish.conf.in?id=e9926f80c6553fde50ce1fcfd38d6370f841efd2'>build: Binary tarball now populates the "current-guix" profile.</a><span class='msg-avail'>...<span class='msg-tooltip'>* Makefile.am (guix-binary.%.tar.xz): Pass
'--profile-name=current-guix'.  Remove glibc and glibc-utf8-locales.
* doc/guix.texi (Binary Installation): Update accordingly.
* etc/guix-install.sh
* etc/guix-install.sh (sys_create_store, sys_enable_guix_daemon)
(sys_authorize_build_farms): Likewise.
* etc/guix-publish.conf.in, etc/guix-publish.service.in,
etc/guix-daemon.conf.in, etc/guix-daemon.service.in: Update file names
accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-03-06 13:25:51 -0500'>2017-03-06</span></td><td><a href='/guix/commit/etc/guix-publish.conf.in?id=613d0895b92c677e0639d5e77c55043e38e020c8'>build: Don't embed absolute paths in .service and .conf service files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Otherwise, users will be stuck running an old copy of guix and the guix-daemon
if they copy the service files instead of symlinking them.

* etc/guix-daemon.conf.in, etc/guix-daemon.service.in, etc/guix-publish.conf.in,
etc/guix-publish.service.in: Expand @localstatedir@ instead of @bindir@.
* nix/local.mk (etc/guix-%.service, etc/guix-%.conf): Use @localstatedir@
instead of @bindir@.
</span></span></td><td>Leo Famulari</td></tr>