My Macrolet

my-macrolet.lisp

(in-package :cl-user)

(defmacro my-macrolet (&environment env bindings &body body)
  (let* ((local-macros
           (loop for (name lambda-list . body) in bindings
                 for macro-lambda = (sb-cltl2:parse-macro name lambda-list body)
                 for macro-fun = (sb-cltl2:enclose macro-lambda env)
                 collect `(,name ,macro-fun)))
         (new-env (sb-cltl2:augment-environment env :macro local-macros)))
    (sb-cltl2:macroexpand-all `(locally ,@body) new-env)))

(my-macrolet ((twice (x) `(+ ,x ,x)))
  (let ((x 0))
    (twice (incf x))))
;=> 3