Texinfo writer: use @sup and @sub instead of custom macros

Fixes #4728

src/Text/Pandoc/Writers/Texinfo.hs

@@ -56,8 +56,6 @@ import Text.Printf (printf)
 
 data WriterState =
   WriterState { stStrikeout   :: Bool  -- document contains strikeout
-              , stSuperscript :: Bool -- document contains superscript
-              , stSubscript   :: Bool -- document contains subscript
               , stEscapeComma :: Bool -- in a context where we need @comma
               , stIdentifiers :: Set.Set String -- header ids used already
               , stOptions     :: WriterOptions -- writer options
@@ -74,8 +72,7 @@ type TI m = StateT WriterState m
 writeTexinfo :: PandocMonad m => WriterOptions -> Pandoc -> m Text
 writeTexinfo options document =
   evalStateT (pandocToTexinfo options $ wrapTop document)
-  WriterState { stStrikeout = False, stSuperscript = False,
-                stEscapeComma = False, stSubscript = False,
+  WriterState { stStrikeout = False, stEscapeComma = False,
                 stIdentifiers = Set.empty, stOptions = options}
 
 -- | Add a "Top" node around the document, needed by Texinfo.
@@ -102,8 +99,6 @@ pandocToTexinfo options (Pandoc meta blocks) = do
   let context = defField "body" body
               $ defField "toc" (writerTableOfContents options)
               $ defField "titlepage" titlePage
-              $ defField "subscript" (stSubscript st)
-              $ defField "superscript" (stSuperscript st)
               $
         defField "strikeout" (stStrikeout st) metadata
   case writerTemplate options of
@@ -427,14 +422,12 @@ inlineToTexinfo (Strikeout lst) = do
   return $ text "@textstrikeout{" <> contents <> text "}"
 
 inlineToTexinfo (Superscript lst) = do
-  modify $ \st -> st{ stSuperscript = True }
   contents <- inlineListToTexinfo lst
-  return $ text "@textsuperscript{" <> contents <> char '}'
+  return $ text "@sup{" <> contents <> char '}'
 
 inlineToTexinfo (Subscript lst) = do
-  modify $ \st -> st{ stSubscript = True }
   contents <- inlineListToTexinfo lst
-  return $ text "@textsubscript{" <> contents <> char '}'
+  return $ text "@sub{" <> contents <> char '}'
 
 inlineToTexinfo (SmallCaps lst) =
   inlineListToTexinfo lst >>= return . inCmd "sc"