(annot:defannotation fntype (args result form)
    (:arity 3)
  (let* ((last-form (cl-annot.util:progn-form-last form))
         (symbol (cl-annot.util:definition-form-symbol last-form)))
    `(progn (declaim (ftype (function ,args ,result) ,symbol))
            ,form)))

;; Usage:
;;    (ql:quickload :cl-syntax)
;;    (syntax:use-syntax :annot)
;;
;;    @fntype (fixnum) fixnum
;;    (defun fib (n)
;;      (if (<= n 1)
;;          1
;;          (+ (fib (1- n)) (fib (- n 2)))))
;;
;;    ;; OK
;;    (defun fib10 () (fib 10))
;;
;;    ;; Compilation Warning
;;    (defun fibx () (fib 'x))
;;
;;    ; caught WARNING:
;;    ;   Constant X conflicts with its asserted type FIXNUM.
;;    ;   See also:
;;    ;     The SBCL Manual, Node "Handling of Types"
;;    ;
;;    ; compilation unit finished
;;    ;   caught 1 WARNING condition