Aw, no Rasp variant? Let's brainstorm it up...
(defun read (path)
(declare (generic P (AsRef Path))
(type P path)
(returns (io:Result (Vector U8))))
(flet ((inner (path)
(declare (type (Ref Path) p)
(returns (io:Result (Vector U8))))
(try-let ((file (File:open path))
(bytes (vector)))
(declare (mutable file bytes))
(try (read-to-end file bytes)
(Ok bytes)))))
(inner (as-ref path))))