12345678910111213141516171819202122232425open!ImportincludeInvariant_intfletraise_s=Error.raise_sletinvariantheretsexp_of_tf:unit=tryf()with|exn->raise_s(Sexp.message"invariant failed"["",Source_code_position0.sexp_of_there;"exn",sexp_of_exnexn;"",sexp_of_tt]);;letcheck_fieldtffield=tryf(Field.getfieldt)with|exn->raise_s(Sexp.message"problem with field"["field",sexp_of_string(Field.namefield);"exn",sexp_of_exnexn]);;