_set :: DynFlags -> Maybe Language -> DynFlags
lang_set dflags lang =
   dflags {
            language = lang,
            extensionFlags = flattenExtensionFlags lang (extensions dflags)
          }

--
lang_set :: DynFlags -> Maybe Language -> DynFlags
lang_set dflags lang =
   dflags {
            language = lang,
            extensionFlags = flattenExtensionFlags lang (extensions dflags)
          }
lang_set dflags lang =
   dflags {
            language = lang,
            extensionFlags = flattenExtensionFlags lang (extensions dflags)
          }