jan kili (Jan 18 2022 at 17:01): jan kili (Jan 18 2022 at 17:01)::gift_heart: New library! Pseudo-random number generators: https://github.com/JanCVanB/roc-random
This is only a v0.1 release, with minimally-usable implementations of 8/16/32-bit PCG-RXS-M-XS. I intend to make its API more ergonomic in v0.2, so I'd love to hear how you think v0.1 feels to use! :smile:
Anton (Jan 18 2022 at 19:36):I put example.roc and Random.roc in examples/cli(commit 2cbac921f), executed cargo run examples/cli/example.rocand got:
thread '<unnamed>' panicked at 'Found unbound type variables {102}
in type alias `Random.Seed8` [] : [ Global('Seed8') (Alias `Num.U8`[ but actually (Alias `Num.Num` (Alias `Num.Integer` (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ])[ but actually [ Private(`Num.@Integer`) (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ]) ] ])[ but actually [ Private(`Num.@Num`) (Alias `Num.Integer` (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ])[ but actually [ Private(`Num.@Integer`) (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ]) ] ]) ] ]) ]) ]<102>', compiler/can/src/scope.rs:192:17
Did you happen to come across this error before @JanCVanB?
jan kili (Jan 18 2022 at 19:42)::thinking: I haven't. That's a lot of but actually lol
jan kili (Jan 18 2022 at 20:00):I just tested cargo run examples/cli/example.roc for the first time (I usually build roc for release and run it with that executable), and I get the same error message that you did. Investigating!
jan kili (Jan 18 2022 at 20:31):Yes, building for release (cargo build --release) and using that executable (./target/release/roc examples/cli/example.roc) seems to work.
jan kili (Jan 18 2022 at 20:31):Does anyone know if there is a difference between roc foo.roc and cargo run foo.roc?
jan kili (Jan 18 2022 at 20:32):Whoa! This might be the culprit, does cargo run use a dev/debug runner by default?
[nix-shell:~/code/clones/roc/examples/cli]$ cargo run example.roc
Finished dev [unoptimized + debuginfo] target(s) in 0.29s
Running `/Users/jan/code/clones/roc/target/debug/roc example.roc`
...
Okay, I have a solution for you @Anton , just use the release build/runner/option/thing! cargo run --release examples/cli/example.roc :smile:
Folkert de Vries (Jan 18 2022 at 20:35):eh, what?
Folkert de Vries (Jan 18 2022 at 20:39):but really, the presence of the --release flag matters for whether the compiler hits a panic or produces a working executable?
jan kili (Jan 18 2022 at 20:40):It seems yes, is that bad?
[nix-shell:~/code/clones/roc]$ cargo run examples/cli/example.roc
Finished dev [unoptimized + debuginfo] target(s) in 0.28s
Running `target/debug/roc examples/cli/example.roc`
thread '<unnamed>' panicked at 'Found unbound type variables {102}
in type alias `Random.Seed8` [] : [ Global('Seed8') (Alias `Num.U8`[ but actually (Alias `Num.Num` (Alias `Num.Integer` (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ])[ but actually [ Private(`Num.@Integer`) (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ]) ] ])[ but actually [ Private(`Num.@Num`) (Alias `Num.Integer` (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ])[ but actually [ Private(`Num.@Integer`) (Alias `Num.Unsigned8`[ but actually [ Private(`Num.@Unsigned8`) ] ]) ] ]) ] ]) ]) ]<102>', compiler/can/src/scope.rs:192:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
^C
[nix-shell:~/code/clones/roc]$ cargo run --release examples/cli/example.roc
Finished release [optimized] target(s) in 0.29s
Running `target/release/roc examples/cli/example.roc`
🔨 Rebuilding host... Done!
a: 18
b: 18
c: 15
d: 15
e: 17
f: 17
g: 14
h: 14
i: 12
j: 12
k: 19
l: 19
:)
[nix-shell:~/code/clones/roc]$
Context: This is for roc-random's example module (and the Random.roc library interface) copied (and only modified so that the platform path is correct) into the Roc repo's examples/cli/ dir.
Folkert de Vries (Jan 18 2022 at 21:01):oh, ah, no it's fine given that specific error
jan kili (Jan 18 2022 at 21:18):Can I improve the library to not fail in that way, or is it a temporary problem with the dev/debug runner?
Folkert de Vries (Jan 18 2022 at 21:41):my guess is you're using closures a bunch
Folkert de Vries (Jan 18 2022 at 21:41):and that is hitting this code path
Folkert de Vries (Jan 18 2022 at 21:42):the check that fails is (clearly) not needed for producing programs, but usually when it fails something is wrong
Folkert de Vries (Jan 18 2022 at 21:42):you can safely comment it locally though
jan kili (Jan 18 2022 at 22:34):Thanks, I'd love to know more! What part should I comment(-out?), and which part of the code is a closure? Something related to Seed8?
Folkert de Vries (Jan 18 2022 at 22:48):oh no the assert that makes it fail
jan kili (Jan 18 2022 at 22:59):Ah, I guess what I'm actually asking is this: What can I do as a library author to prevent its users from experiencing this compiler panic when using the library with cargo run without --release?
Folkert de Vries (Jan 18 2022 at 23:06):oh, nothing I think
Richard Feldman (Jan 18 2022 at 23:24):this is one of those "something we believed was true turned out not to be, so crash" assertions
Richard Feldman (Jan 18 2022 at 23:25):we want it to be noisy so we can investigate it and ideally solve the cause rather than the symptom
Richard Feldman (Jan 18 2022 at 23:27):but we skip those checks altogether in release builds, so on the one hand we don't get the feedback but on the other hand it might happen to work anyway (as it seems to here) despite our assumption being broken :big_smile:
Folkert de Vries (Jan 18 2022 at 23:31):oh, no this is something that should be true but we have slipped up
Folkert de Vries (Jan 18 2022 at 23:31):it's just that usually the effect is not noticable
jan kili (Jan 18 2022 at 23:32):Is cargo run designed for compiler debugging, app debugging, or app execution?
Folkert de Vries (Jan 18 2022 at 23:34):mostly speed
Folkert de Vries (Jan 18 2022 at 23:34):it compiles faster
Folkert de Vries (Jan 18 2022 at 23:35):also you get more info if something panics, or if you use a debugger
jan kili (Jan 18 2022 at 23:45):Cool, so then as a library author I'll test to both (release and nonrelease) and report issues with either?
Folkert de Vries (Jan 18 2022 at 23:51):well that should not be necessary
Folkert de Vries (Jan 18 2022 at 23:51):we'll get this sorted out now that we have an example that actually fails the assert
jan kili (Jan 18 2022 at 23:56):High five for the co-discovery, @Anton ! :high_five:️
jan kili (Jan 19 2022 at 07:00):One last thing, the roc docs website generator is lovely: https://jancvanb.github.io/roc-random/
Lucas Rosa (Jan 19 2022 at 19:52):that's pretty stuff :D
Last updated: Jul 26 2025 at 12:14 UTC