invariant here t sexp_of_t f runs f (), and if f raises, wraps the exception
in an Error.t that states "invariant failed" and includes both the exception
raised by f, as well as sexp_of_t t. Idiomatic usage looks like:
invariant [%here] t <:sexp_of< t >> (fun () ->
... check t's invariants ... )
For polymorphic types:
let invariant check_a t =
Invariant.invariant [%here] t <:sexp_of< _ t >> (fun () -> ... )
It's okay to use <:sexp_of< _ t >> because the exceptions raised by check_a
will show the parts that are sexp_opaque at top-level.
check_field is used when checking invariants using Fields.iter. It wraps an
exception raised when checking a field with the field's name. Idiomatic usage looks
like:
type t =
{ foo : Foo.t;
bar : Bar.t;
}
with fields
let invariant t : unit =
invariant "Foo.invariant" t <:sexp_of< t >> (fun () ->
let check f = Invariant.check_field t f in
Fields.iter
~foo:(check Foo.invariant)
~bar:(check Bar.invariant))
;;