Add helpers for let handler

src/render/shader/walker.lisp

@@ -27,6 +27,26 @@
   "Retreive the handler for the symbol FIRST."
   (gethash first *form-handlers* *default-handler*))
 
+(defun binding-to-symbol (binding)
+  (let ((name (safe-first binding)))
+    (cond ((listp name)
+           (assert (eq 'setf (first name)))
+           (check-type (second name) symbol)
+           (second name))
+          (t
+           name))))
+
+(defmacro with-imposed-bindings (&body body)
+  #-sbcl
+  `(locally ,@body)
+  #+sbcl
+  (destructuring-bind ((binder bindings &rest binder-body))
+      body
+    `(locally
+         (declare (sb-ext:disable-package-locks
+                   ,@(mapcar 'binding-to-symbol bindings)))
+       (,binder ,bindings ,@binder-body))))
+
 (defun function-name-p (name)
   "Return whether NAME is the name of a function."
   (or (symbolp name)