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
 
 
le>
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<div class='path'>path: <a href='/guix/log/?id=948793cb4f83d84f32a871779d057856de87bdb5'>root</a>/<a href='/guix/log/tests?id=948793cb4f83d84f32a871779d057856de87bdb5'>tests</a>/<a href='/guix/log/tests/store-roots.scm?id=948793cb4f83d84f32a871779d057856de87bdb5'>store-roots.scm</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/store-roots.scm?id=948793cb4f83d84f32a871779d057856de87bdb5&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
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<tr><td><span title='2020-05-05 23:45:56 +0200'>2020-05-05</span></td><td><a href='/guix/commit/po/doc/guix-manual.ru.po?id=0701274446bbd39b053a0c65947fd7f1319f7bf6'>nls: Update.</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-04-12 00:18:05 +0200'>2020-04-12</span></td><td><a href='/guix/commit/po/doc/guix-manual.ru.po?id=935ef44b398353b5b6af94e185d7b0c3d833db0b'>nls: Update.</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-03-23 00:06:58 +0100'>2020-03-23</span></td><td><a href='/guix/commit/po/doc/guix-manual.ru.po?id=86603d8660e42a3b5d8b407e456a98429943bc7e'>nls: Update.</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-05-13 10:46:03 +0200'>2019-05-13</span></td><td><a href='/guix/commit/po/doc/guix-manual.ru.po?id=3bac7e6495934de9913e6186d954d1331883e064'>doc: Add Russian translation.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/local.mk (info_TEXINFOS): Add guix.ru.texi.
(TRANSLATED_INFO): Add {guix,contributing}.ru.texi.
* po/doc/local.mk (DOC_PO_FILES): Add guix-manual.ru.po.
* po/doc/guix-manual.ru.po: New file.
</span></span></td><td>Ludovic Courtès</td></tr>