Remove `haddock-test`'s dep. on `syb` (#987)

The functionality is easily inlined into one short function: `gmapEverywhere`.
This doesn't warrant pulling in another package.

2 files changed, 13 insertions, 7 deletions

diff --git a/haddock-test/haddock-test.cabal b/haddock-test/haddock-test.cabal
index 48314600..23b5953c 100644
--- a/haddock-test/haddock-test.cabal
+++ b/haddock-test/haddock-test.cabal
@@ -16,7 +16,7 @@ library
   default-language: Haskell2010
   ghc-options: -Wall
   hs-source-dirs:   src
-  build-depends:    base >= 4.3 && < 4.13, bytestring, directory, process, filepath, Cabal, xml, xhtml, syb
+  build-depends:    base >= 4.3 && < 4.13, bytestring, directory, process, filepath, Cabal, xml, xhtml
 
   exposed-modules:
     Test.Haddock
diff --git a/haddock-test/src/Test/Haddock/Xhtml.hs b/haddock-test/src/Test/Haddock/Xhtml.hs
index 8bfc973f..d4520100 100644
--- a/haddock-test/src/Test/Haddock/Xhtml.hs
+++ b/haddock-test/src/Test/Haddock/Xhtml.hs
@@ -1,5 +1,8 @@
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE GADTs #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Test.Haddock.Xhtml
@@ -8,10 +11,7 @@ module Test.Haddock.Xhtml
     , stripLinks, stripLinksWhen, stripAnchorsWhen, stripFooter
     ) where
 
-
-import Data.Generics.Aliases
-import Data.Generics.Schemes
-
+import Data.Data ( Data(..), Typeable, eqT, (:~:)(..) )
 import Text.XML.Light
 import Text.XHtml (Html, HtmlAttr, (!))
 import qualified Text.XHtml as Xhtml
@@ -26,6 +26,12 @@ deriving instance Eq Element
 deriving instance Eq Content
 deriving instance Eq CData
 
+-- | Similar to @everywhere (mkT f) x@ from SYB.
+gmapEverywhere :: forall a b. (Data a, Typeable b) => (b -> b) -> a -> a
+gmapEverywhere f x = gmapT (gmapEverywhere f) $ case eqT @a @b of
+                                                  Nothing -> x
+                                                  Just Refl -> f x
+
 
 parseXml :: String -> Maybe Xml
 parseXml = fmap Xml . parseXMLDoc
@@ -58,12 +64,12 @@ stripAnchorsWhen p =
 
 
 processAnchors :: (Attr -> Attr) -> Xml -> Xml
-processAnchors f = Xml . everywhere (mkT f) . xmlElement
+processAnchors f = Xml . gmapEverywhere f . xmlElement
 
 
 stripFooter :: Xml -> Xml
 stripFooter =
-    Xml . everywhere (mkT defoot) . xmlElement
+    Xml . gmapEverywhere defoot . xmlElement
   where
     defoot el
         | isFooter el = el { elContent = [] }