+ (let ((lvar (nth (1- n) (combination-args call))))
+ (when (and lvar (constant-lvar-p lvar))
+ (careful-specifier-type (lvar-value lvar))))))
+
+;;; Derive the type to be the type specifier which is the Nth arg,
+;;; with the additional restriptions noted in the CLHS for STRING and
+;;; SIMPLE-STRING, defined to specialize on CHARACTER, and for VECTOR
+;;; (under the page for MAKE-SEQUENCE).
+(defun creation-result-type-specifier-nth-arg (n)
+ (lambda (call)
+ (declare (type combination call))
+ (let ((lvar (nth (1- n) (combination-args call))))
+ (when (and lvar (constant-lvar-p lvar))
+ (let* ((specifier (lvar-value lvar))
+ (lspecifier (if (atom specifier) (list specifier) specifier)))
+ (cond
+ ((eq (car lspecifier) 'string)
+ (destructuring-bind (string &rest size)
+ lspecifier
+ (declare (ignore string))
+ (careful-specifier-type
+ `(vector character ,@(when size size)))))
+ ((eq (car lspecifier) 'simple-string)
+ (destructuring-bind (simple-string &rest size)
+ lspecifier
+ (declare (ignore simple-string))
+ (careful-specifier-type
+ `(simple-array character ,@(if size (list size) '((*)))))))
+ (t
+ (let ((ctype (careful-specifier-type specifier)))
+ (if (and (array-type-p ctype)
+ (eq (array-type-specialized-element-type ctype)
+ *wild-type*))
+ ;; I don't think I'm allowed to modify what I get
+ ;; back from SPECIFIER-TYPE; it is, after all,
+ ;; cached. Better copy it, then.
+ (let ((real-ctype (copy-structure ctype)))
+ (setf (array-type-element-type real-ctype)
+ *universal-type*
+ (array-type-specialized-element-type real-ctype)
+ *universal-type*)
+ real-ctype)
+ ctype)))))))))