(else
           (recur (condition-type-supertype subtype))))))

(define (condition-type-field-supertype condition-type field)
  (let loop ((condition-type condition-type))
    (cond ((not condition-type) #f)
          ((memq field (condition-type-fields condition-type))
           condition-type)
          (else
           (loop (condition-type-supertype condition-type))))))

; The type-field-alist is of the form
; ((&lt;type&gt; (&lt;field-name&gt; . &lt;value&gt;) ...) ...)
(define-record-type :condition