Clojurians Log v2
Clojure programming
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core-async
shaunlebron 2025-11-26T22:11:44.900769Z
Is this a bug?
(go (letfn [(foo [])]
(Assert failed: 
ghadi 2025-11-26T22:13:57.131489Z
the fns inside letfn are new fn scopes, and go only rewrites the immediate fn scope
ghadi 2025-11-26T22:16:15.337589Z
...so it's fairly accurate
shaunlebron 2025-11-26T22:27:52.056009Z
maybe I don’t know how letfn works, but is not inside a function, right?
2025-11-26T22:52:37.137749Z
Sure looks like a bug to me
seancorfield 2025-11-26T22:53:24.101149Z
Which version of core.async @shaunlebron?
> clj
Clojure 1.12.3
user=> (add-lib 'org.clojure/core.async)
[org.clojure/core.async org.clojure/core.cache org.clojure/core.memoize org.clojure/data.priority-map org.clojure/tools.analyzer org.clojure/tools.analyzer.jvm org.clojure/tools.reader org.ow2.asm/asm]
user=> (require '[clojure.core.async :refer [go <! timeout]])
nil
user=> (go (letfn [(foo [])] (<! (timeout 10))))
#object[clojure.core.async.impl.channels.ManyToManyChannel 0xae73c80 "clojure.core.async.impl.channels.ManyToManyChannel@ae73c80"]shaunlebron 2025-11-26T22:54:10.145939Z
[org.clojure/clojure "1.12.1"]
[org.clojure/core.async "1.8.741"]seancorfield 2025-11-26T22:56:19.690209Z
I can repro with 1.8.741 but not with the most recent version.
shaunlebron 2025-11-26T22:57:09.039259Z
I was running it from my repl, in my giant lein project
2025-11-26T22:59:07.941559Z
Looks like maybe missing handling of the :letfn* tools.analyzer ast node
seancorfield 2025-11-26T23:01:00.998199Z
1.9.808-alpha1 shows that error but 1.9.829-alpha2 doesn't, for me.
Alex Miller (Clojure team) 2025-11-26T23:03:27.807239Z
if you're using the latest alpha on a new jvm, then you're running go in a virtual thread, which is not using the go analyzer
Alex Miller (Clojure team) 2025-11-26T23:03:59.289009Z
I'm pretty sure there is a jira for letfn in go
seancorfield 2025-11-26T23:04:54.363839Z
Ah, I'd forgotten that...
ghadi 2025-11-26T23:11:16.917289Z
letfn bindings are new fn contexts, go cannot rewrite through
2025-11-26T23:14:37.570779Z
The op is in the body of the letfn
2025-11-26T23:15:13.824799Z
Not one of fns
ghadi 2025-11-26T23:16:10.280229Z
oh I misread
ghadi 2025-11-26T23:16:17.977969Z
indentation threw me off
seancorfield 2025-11-26T23:17:23.250059Z
(go (letfn [] (<! (timeout 10)))) fails too 🙂
🙏 1
2025-11-26T23:30:51.859319Z
Gobsmacked not to have run into this permutation before
seancorfield 2025-11-27T00:40:07.375319Z
From 2018!!!
shaunlebron 2025-11-27T01:20:53.005189Z
nobody uses letfn lol
shaunlebron 2025-11-27T01:21:47.459539Z
I only started using it recently to reduce the indentation of nested functions, works really well for that
2025-11-27T02:46:12.686009Z
https://github.com/hiredman/clojure/blob/readerIII/src/clj/clojure/reader.clj#L165 letfn and I go back like spinal cords and car seats