maybe_underscore :: SDoc -> SDoc
maybe_underscore doc
  | underscorePrefix = pp_cSEP <> doc
  | otherwise        = doc
maybe_underscore :: SDoc -> SDoc
maybe_underscore doc
  | underscorePrefix = pp_cSEP <> doc
  | otherwise        = doc
maybe_underscore doc
  | underscorePrefix = pp_cSEP <> doc
  | otherwise        = doc