(** The invariant harness -- validation layer 2. Checks run over a *liturgical*
    year, not a civil year: a season that straddles January would otherwise look
    as though it recurs. *)
type failure = { year : int; date : string; check : string; detail : string }

val failure_to_string : failure -> string

(** [run vocab ~year_start ~temporal ~year] returns every invariant violation in
    the liturgical year opening in civil year [year]. An empty list means the
    year is clean. *)
val run :
  ('s, 'r) Vocab.t ->
  year_start:(int -> Date.t) ->
  temporal:(Date.t -> ('s, 'r) Temporal.t) ->
  year:int ->
  failure list