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