message: Improve formatting in stratification
diff: synth_type Context (core.int_intro Int) (typ int_type) (expr (stratified.int_intro Int)).
  % Arrays
  - is_type Context (core.array_type Type LenElem) (typ (stratified.array_type Type' LenElem')) :-
  + is_type Context (core.array_type Type LenElem)
  + (typ (stratified.array_type Type' LenElem'))
  + :-
  check_type Context Type (kind type_type) (typ Type'),
  check_type Context LenElem (typ int_type) (expr LenElem').
  - check_type Context (core.array_type Type LenElem) (kind type_type) (typ (stratified.array_type Type' LenElem')) :-
  + check_type Context (core.array_type Type LenElem) (kind type_type)
  + (typ (stratified.array_type Type' LenElem'))
  + :-
  check_type Context Type (kind type_type) (typ Type'),
  check_type Context LenElem (typ int_type) (expr LenElem').
  - check_type Context (core.array_intro Elems) (typ (array_type Type (int_intro Len))) (expr (stratified.array_intro Elems')) :-
  + check_type Context (core.array_intro Elems) (typ (array_type Type (int_intro Len)))
  + (expr (stratified.array_intro Elems'))
  + :-
  length Elems Len,
  - map (fun elem_term elem_term' => check_type Context elem_term (typ Type) (expr elem_term')) Elems Elems'.
  - synth_type Context (core.array_elim ArrayElem IndexElem) (typ Type) (expr (stratified.array_elim ArrayElem' IndexElem')) :-
  + map (fun elem_term elem_term' =>
  + check_type Context elem_term (typ Type) (expr elem_term')
  + )
  + Elems Elems'.
  + synth_type Context (core.array_elim ArrayElem IndexElem) (typ Type)
  + (expr (stratified.array_elim ArrayElem' IndexElem'))
  + :-
  % FIXME: ensure `IndexElem` is in array bounds, possibly with refinement types?
  synth_type Context ArrayElem (typ (array_type Type _)) (expr ArrayElem'),
  check_type Context IndexElem (typ int_type) (expr IndexElem').
  