In the patch "Tuple tycons have parens around their names", the names
of the tuple tycons were changed to include parens, but isTupleTyCon
was not updated to match, which made tuple types show as "(,) a b"
rather than "(a,b)"
showsPrec _ (TyCon _ s) = showString s
isTupleTyCon :: TyCon -> Bool
-isTupleTyCon (TyCon _ (',':_)) = True
-isTupleTyCon _ = False
+isTupleTyCon (TyCon _ ('(':',':_)) = True
+isTupleTyCon _ = False
-- Some (Show.TypeRep) helpers: