(define-signature-form sig-form-id expr)
(define-signature-form (sig-form-id id) body ...+) (define-signature-form (sig-form-id id intro-id) body ...+)
In the first form, the result of expr must be a transformer procedure that accepts one argument. In the second form, sig-form-id is bound to a transformer procedure whose argument is id and whose body is the bodys. The third form is like the second one, but intro-id is bound to a procedure that is analogous to syntax-local-introduce for the signature-form expansion.
The result of the transformer procedure must be a list of syntax objects, which are substituted for a use of sig-form-id in a define-signature expansion. (The result is a list so that the transformer can produce multiple declarations; define-signature has no splicing begin form.)
Changed in version 22.214.171.124 of package base: Added support for the form with a transformer expr.
(struct/ctc id ([field contract-expr] ...) struct-option ...)
field = id | [id #:mutable] struct-option = #:mutable | #:omit-constructor | #:omit-define-syntaxes | #:omit-define-values