Odd name-sensitive behaviour

[Chris Spencer]

Was just trying out some basic protocol/datatype types and found an odd case where the naming of the protocol changes whether an exception is thrown or not.

(ns typingfun.core

  (:require [clojure.core.typed :as t]))

(t/ann-protocol AddProtoc

  adder [AddProtoc Number -> AddProtoc])

(t/defprotocol> AddProtoc

  (adder [this amount]))

(t/ann-datatype Accumulator [t :- Number])

(deftype Accumulator [t]

  AddProtoc

  (adder [_ i] (Accumulator. (+ t i))))

(t/ann t [Number -> Accumulator])

(defn t [i] (Accumulator. i))

(t/ann t2 [Number -> AddProtoc])

(defn t2 [i] (Accumulator. i))

(t/check-ns)

"Checking line:" 4

"Checking line:" 7

"Checking line:" 10

"Checking line:" 12

"Checking line:" 16

"Checking line:" 17

"Checking line:" 19

"Checking line:" 20

IllegalArgumentException Multiple methods in multimethod 'subtype*' match dispatch value: [clojure.core.typed.Protocol clojure.core.typed.Protocol :clojure.core.typed/clojure] -> [clojure.core.typed.Protocol :clojure.core.typed/Type :clojure.core.typed/clojure] and [clojure.core.typed.Protocol clojure.core.typed.Protocol :clojure.core.typed/default], and neither is preferred  clojure.lang.MultiFn.findAndCacheBestMethod (MultiFn.java:136)

Doesn't occur if name of protocol changed to AddProto. The same exception is thrown when named AddProto but with an incompatible type given for the adder in the protocol (such as [AddProto Number -> Number]). Both are thrown on line 20 (the checking of t2)

This is with clojure 1.4 on windows.

[Chris Spencer]

Of course, I realise the actual issue just after posting: can't just reload the namespace in repl. So that's a bit more understandable.

However, setting the protocol definition to:

(t/ann-protocol AddProtoc

  adder [AddProtoc Number -> Number])

With the above code now checks fine, even though adder returns an Accumulator in its definition.

[Ambrose Bonnaire-Sergeant]

(Accidentally didn't to send this to the list)

On Wed, Mar 20, 2013 at 9:00 PM, Chris Spencer <chris.ag...@gmail.com> wrote:

Seems the return type isn't being checked properly in some circumstances. If I set the type of adder to something like [AddProtocol Number -> String] then:

(adder [this i]

  (let [ret (Accumulator. (+ total i))]

    ret))

Properly complains, whereas:

(adder [this i]

  (Accumulator. (+ total i)))

does not.

Thanks, that really helps narrow the problem. I've created an issue: http://dev.clojure.org/jira/browse/CTYP-21

 

The naming issues seem to be an artefact of reloading a type checked namespace in the repl after changing the name of a type or protocol, with is easy to live with. (renaming protocols/types in reloaded namespaces always tends to bad behaviour anyway).

The way it currently works is meant to help with REPL driven development. Just re-evaluating an ann-protocol should update its type. The unsurprisingly comes with all the pitfalls of (a persistent) REPL.

Thanks for your work on this by the way, impressive work!

Cheers!

Ambrose

[Ambrose Bonnaire-Sergeant]

Chris,

I can't reproduce the problem: https://github.com/clojure/core.typed/blob/master/src/test/clojure/clojure/core/typed/test/core.clj#L1210

Thanks,

Ambrose

[Ambrose Bonnaire-Sergeant]

Doh, I probably can't reproduce because I just fixed it yesterday :)

https://github.com/clojure/core.typed/commit/59cb1c43e49b8dccb566756d5836a31958beec31

I've resolved the issue on Jira.

Thanks,

Ambrose