core-async 2021-05-25 | Slack Archive

is there some convenient way to macro expand go blocks? Can't figure out how to propagate the env correctly

What do you mean by “convenient”? Regular macroexpand works, but the output is quite…. verbose.

(macroexpand-1
 '(clojure.core.async/go
   (let [ret (clojure.core.async/<! (clojure.core.async/go :hello))]
    (println ret))))

Ben Sless06:05:09

Now try binding a channel outside the go block

Joshua Suskalo14:05:18

There's macroexpand-all from clojure.walk

noisesmith16:05:13

> Can't figure out how to propagate the env correctly > Now try binding a channel outside the go block what behavior are you seeing? in macro expansion, a binding from outside the block should just show up as opaque

noisesmith16:05:56

is it this error?

Syntax error macroexpanding >/go at (REPL:1:1).
Could not resolve var: c

this is because go does some "clever" code rewriting, in my experience it doesn't take much to confuse it

(ins)user=> (require '[clojure.core.async :as >])
nil
(ins)user=> (macroexpand '(let [c (>/chan)] (>/go (let [ret (>/<! (>/go (>/<! c)))] (println ret)))))
(let* [c (>/chan)] (>/go (let [ret (>/<! (>/go (>/<! c)))] (println ret))))
(ins)user=> (require '[clojure.walk :refer [macroexpand-all]])
nil
(ins)user=> (macroexpand-all '(let [c (>/chan)] (>/go (let [ret (>/<! (>/go (>/<! c)))] (println ret)))))
Syntax error macroexpanding >/go at (REPL:1:1).
Could not resolve var: c

*edit: added more context to the error message

noisesmith16:05:09

I think that's what's going on here at least

Ben Sless18:05:46

Even simpler example

(macroexpand-1 '(a/go (a/<! c)))

Ben Sless18:05:04

go relies on &env

2021-05-25

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