Compatibility with GHC 8.10 and template-haskell 2.16.

Taken from 
https://raw.githubusercontent.com/archlinux/svntogit-community/packages/haskell-language-haskell-extract/trunk/ghc-8.10.patch

diff --git a/src/Language/Haskell/Extract.hs b/src/Language/Haskell/Extract.hs
index 3e8958b..43dfe04 100644
--- a/src/Language/Haskell/Extract.hs
+++ b/src/Language/Haskell/Extract.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 module Language.Haskell.Extract (
   functionExtractor,
   functionExtractorMap,
@@ -25,7 +26,11 @@ extractAllFunctions pattern =
 functionExtractor :: String -> ExpQ
 functionExtractor pattern =
   do functions <- extractAllFunctions pattern
-     let makePair n = TupE [ LitE $ StringL n , VarE $ mkName n]
+     let makePair n = TupE
+#if MIN_VERSION_template_haskell(2,16,0)
+                           $ map Just
+#endif
+                           [ LitE $ StringL n , VarE $ mkName n]
      return $ ListE $ map makePair functions
 
 
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<div class='path'>path: <a href='/guix/log/?id=d8fed768a899bd0a3a84a88572135a1d7bde2400'>root</a>/<a href='/guix/log/tests?id=d8fed768a899bd0a3a84a88572135a1d7bde2400'>tests</a>/<a href='/guix/log/tests/guix-hash.sh?id=d8fed768a899bd0a3a84a88572135a1d7bde2400'>guix-hash.sh</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/tests/guix-hash.sh?id=d8fed768a899bd0a3a84a88572135a1d7bde2400&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-01-04 11:51:48 +0100'>2021-01-04</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=ed63b7f87e88b0ce9c4a78bf0529599de9172b1f'>guix hash: Honor '-H' when used alongside '-r'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/hash.scm (guix-hash): When 'recursive? is true, use
'open-hash-port' instead of 'open-sha256-port'.
* tests/guix-hash.sh: Add test for 'guix hash -r -H sha512'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-lint.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh: Use the shell '!' keyword to negate command exit status
in place of 'if ...; then false; else true; fi'
</span></span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2020-05-22 00:35:24 +0200'>2020-05-22</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=0e4e9c8e7655f3e2a9c2615923768d211ac02a3e'>guix hash, guix download: Support base64 format.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/download.scm (show-help, %options): Support "base64"
format.
* guix/scripts/hash.scm (show-help, %options): Likewise.
* tests/guix-hash.sh: Test it.
* doc/guix.texi (Invoking guix hash): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-22 00:35:24 +0200'>2020-05-22</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=18ae1ec3ecfe22d55d6cdf595a442afebbc5595a'>guix hash, guix download: Add '--hash'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/download.scm (%default-options): Add 'hash-algorithm'.
(show-help, %options): Add "--hash".
(guix-download): Honor it.
* guix/scripts/hash.scm (%default-options): Add 'hash-algorithm'.
(show-help, %options): Add "--hash".
(guix-hash): Honor it.
* tests/guix-hash.sh: Test '-H sha512'.
* doc/guix.texi (Invoking guix download): Document it.
(Invoking guix hash): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>