lsubst n new (LForeign fd rd args)
     = let args' = map (\(d, a) -> (d, lsubst n new a)) args in
           LForeign fd rd args'
lsubst n new (LForeign fd rd args)
     = let args' = map (\(d, a) -> (d, lsubst n new a)) args in
           LForeign fd rd args'
lsubst n new (LForeign fd rd args)
     = let args' = map (\(d, a) -> (d, lsubst n new a)) args in
           LForeign fd rd args'