Comment 50 for bug 313202

Thanks.

What if we were to change the :arg-tn and :result-tn methods to error at runtime? I think it would be more in SBCL's normal style to do something like:

(define-alien-type-method (record :arg-tn) (type state)
  (declare (ignore type state))
  (warn "Passing structs by value is unsupported on this platform.")
  `(error "Passing structs by value is unsupported on this platform."))

instead? This should make it easier to test, too.