define-parse-method (name lambda-list &body body)

type-name -- A symbol naming the new foreign type.
lambda-list -- A lambda list which is the argument list of the new foreign type.
body -- One or more forms that provide a definition of the new foreign type.

THE EXAMPLE IS MISPLACED. Taken from CFFI's :boolean type definition:

  (define-foreign-type :boolean (&optional (base-type :int))
    "Boolean type. Maps to an :int by default. Only accepts integer types."
    (ecase base-type
      ((:char
        :unsigned-char
        :int
        :unsigned-int
        :long
        :unsigned-long) base-type)))


  CFFI> (canonicalize-foreign-type :boolean)
  => :INT
  CFFI> (canonicalize-foreign-type '(:boolean :long))
  => :LONG
  CFFI> (canonicalize-foreign-type '(:boolean :float))
  ;; error--> signalled by ECASE.