Re: GSOC | Extending Common Lisp support

[Charles Turner <chturne at gmail dot com>]

On 27 April 2012 07:20, Helmut Eller <eller.helmut@gmail.com> wrote:
> From a philosophical point of view, type declarations in Lisp don't
> change the semantics, i.e. a program with declarations should produce
> the same results as the program without (though it could be more
> efficient or give extra warnings). ÂIt's also in line with tradition to
> emit a warning at compile time but still generate code that will raise
> an runtime error. ÂIMO Kawa acts quite gracefully here.

My problem with this philosophy, or at least Kawa's interpretation of
it, is that it leaves us with inconsistent error messages. For
instance,

(let ((x :: integer 10.5))
  (+ x 1))

couple of warning, and then a type error. This is nice.

(let ((x :: gnu.lists.Sequence 10))
  (car x))

couple of warnings, and then a ClassCastException, this isn't so nice IMO.