let aux_propagate_arity ar = function
| `Lam(false,`Match(`I(v,args),(x,_),liftno,bs,args')) when not delift_by_one ->
`Lam(false,`Match(`I(v,args),(x,ar),liftno,bs,args'))
let aux_propagate_arity ar = function
| `Lam(false,`Match(`I(v,args),(x,_),liftno,bs,args')) when not delift_by_one ->
`Lam(false,`Match(`I(v,args),(x,ar),liftno,bs,args'))