Use isHeaderBlock from Shared rather than defining it anew...

src/Text/Pandoc/Writers/FB2.hs

@@ -44,7 +44,7 @@ import qualified Text.XML.Light.Cursor as XC
 
 import Text.Pandoc.Definition
 import Text.Pandoc.Options (WriterOptions(..), HTMLMathMethod(..), def)
-import Text.Pandoc.Shared (orderedListMarkers)
+import Text.Pandoc.Shared (orderedListMarkers, isHeaderBlock)
 import Text.Pandoc.Walk
 
 -- | Data to be written at the end of the document:
@@ -157,9 +157,7 @@ renderSection level (ttl, body) = do
                else cMapM blockToXml body
     return $ el "section" (title ++ content)
   where
-    hasSubsections = any isHeader
-    isHeader (Header _ _ _) = True
-    isHeader _ = False
+    hasSubsections = any isHeaderBlock
 
 -- | Only <p> and <empty-line> are allowed within <title> in FB2.
 formatTitle :: [Inline] -> [Content]

src/Text/Pandoc/Writers/Texinfo.hs

@@ -293,7 +293,7 @@ blockListToTexinfo (x:xs) = do
   case x of
     Header level _ _ -> do
       -- We need need to insert a menu for this node.
-      let (before, after) = break isHeader xs
+      let (before, after) = break isHeaderBlock xs
       before' <- blockListToTexinfo before
       let menu = if level < 4
                     then collectNodes (level + 1) after
@@ -315,10 +315,6 @@ blockListToTexinfo (x:xs) = do
       xs' <- blockListToTexinfo xs
       return $ x' $$ xs'
 
-isHeader :: Block -> Bool
-isHeader (Header _ _ _) = True
-isHeader _              = False
-
 collectNodes :: Int -> [Block] -> [Block]
 collectNodes _ [] = []
 collectNodes level (x:xs) =