(in-package :cl-user)

(defmacro read-only (place &optional name) (declare (ignore name)) place)
(define-setf-expander read-only (place &optional (name place))
  (error "You're not supposed to SETF ~S." name))

(defmacro letro (bindings &body body)
  (let ((gensyms (mapcar (lambda (x) (declare (ignore x)) (gensym)) bindings)))
    `(LET ,(mapcar (lambda (b g)
                     `(,g ,@(if (consp b) (cdr b))))
                   bindings gensyms)
       (SYMBOL-MACROLET ,(mapcar (lambda (b g &aux (v (if (consp b) (car b) b)))
                                   `(,v (READ-ONLY ,g ,v)))
                                 bindings gensyms)
         ,@body))))

(defun foo ()
  (letro ((a 42))
    (incf a)                            ;<-- Generates compile-time error
    a))