LaTeX writer: Avoid inadvertently creating ? or ! ligatures.

These are upside down ? and !, resp.

Closes #5407.

src/Text/Pandoc/Writers/LaTeX.hs

@@ -340,6 +340,14 @@ stringToLaTeX context zs = do
                              -> cs <> xs
             _ -> cs <> "{}" <> xs
     in case x of
+         '?' | ligatures ->  -- avoid ?` ligature
+           case xs of
+             '`':_ -> emits "?{}"
+             _     -> emitc x
+         '!' | ligatures ->  -- avoid !` ligature
+           case xs of
+             '`':_ -> emits "!{}"
+             _     -> emitc x
          '{' -> emits "\\{"
          '}' -> emits "\\}"
          '`' | ctx == CodeString -> emitcseq "\\textasciigrave"

test/command/5407.md

@@ -0,0 +1,14 @@
+```
+% pandoc -t latex --wrap=preserve
+hi there?“
+hi there!“
+hi there?‘
+hi there!‘
+hi there!
+^D
+hi there?{}``
+hi there!{}``
+hi there?{}`
+hi there!{}`
+hi there!
+```