type-error-datum condition ⇒ datum
type-error-expected-type condition ⇒ expected-type
| condition | a condition of type type-error. |
| datum | an object. |
| expected-type | a type specifier. |
type-error-datum returns the offending datum in the situation represented by the condition.
type-error-expected-type returns the expected type of the offending datum in the situation represented by the condition.
(defun fix-digits (condition)
(check-type condition type-error)
(let* ((digits '(zero one two three four
five six seven eight nine))
(val (position (type-error-datum condition) digits)))
(if (and val (subtypep 'fixnum (type-error-expected-type condition)))
(store-value 7))))
(defun foo (x)
(handler-bind ((type-error #'fix-digits))
(check-type x number)
(+ x 3)))
(foo 'seven)
⇒ 10