fdef for defmulti?

[Patrik Sundberg]

Hi,

Am I right to think you can't currently fdef a defmulti function? I tried and when running tests using clojure.spec.test/instrument I see:

1. Unhandled java.lang.ClassCastException

   clojure.spec.test$spec_checking_fn$fn__12959 cannot be cast to

   clojure.lang.MultiFn

                  core.clj: 1806  clojure.core/get-method

                  core.clj: 1806  clojure.core/get-method

           time_series.clj:  474  tulos.time-series/eval181936/fn

So I guess what happens is the fdef+instrument adds a normal fn wrapper, which then isn't a multi method and it breaks down.

Has this been discussed before? Any plans? I didn't find anything.

Thanks,

Patrik

[Alex Miller]

There are several kinds of functions that can't currently be spec'ed (primitive, interned, maybe protocol fns?, multi methods). Some of those will ultimately be fixed, some (interned) will probably not.

[Alex Miller]

I should mention that a half step is to spec the dispatch function used by the multimethod. That covers the front-end.

[Patrik Sundberg]

What I meant was that you can spec the defmulti, and code runs just fine, but you can't instrument it. As then you end up with the instrumentation wrapper not being a multimethod, so things break. That's how I read the stack trace. It'd seem possible for instrument to wrap the multimethod with a multimethod stub, so perhaps that's a change to consider.

[Yehonathan Sharvit]

Any update about defmulti and fdef?

[Derek Thurn]

I'm also interested in this functionality. Is there an existing JIRA issue we can follow for allowing specs for multimethods?

[Alex Miller]

I don't think there is a jira issue for it, feel free to add it. Not currently a priority for us but if someone wanted to work on it, I'd be happy to review.

[Tim Sauerwein]

Because fdef is not available for defmulti, I find myself writing a dispatch function by hand instead of using a multimethod.