1234567891011121314151617181920212223242526open!ImportincludeInvariant_intfletraise_s=Error.raise_sletinvariantheretsexp_of_tf:unit=tryf()withexn->raise_s(Sexp.message"invariant failed"["",Source_code_position0.sexp_of_there;"exn",sexp_of_exnexn;"",sexp_of_tt]);;letcheck_fieldtffield=tryf(Field.getfieldt)withexn->raise_s(Sexp.message"problem with field"["field",sexp_of_string(Field.namefield);"exn",sexp_of_exnexn]);;