error.lisp

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;;;; Author: Robert Brown <robert.brown@gmail.com>

;;;; Error generation for missing arguments.

(in-package #:com.google.base)

;; Tell the compiler that MISSING-ARGUMENT never returns in order to avoid compile-time type
;; warnings for object slots with declared types.
(declaim (ftype (function () nil) missing-argument))

(defun missing-argument ()
  "Signal an error indicating that an &OPTIONAL or &KEY argument is missing.
Use (MISSING-ARGUMENT) as the default value of required &KEY function arguments
and as the initform in DEFCLASS and DEFSTRUCT slot definition forms when the
slot's initform must always be supplied to MAKE-INSTANCE."
  (error "A required &KEY or &OPTIONAL argument was not supplied."))