Chris (Mar 28 2023 at 12:06): Chris (Mar 28 2023 at 12:06):Hi! Which rust toolchain should I use to run builds and tests on main? After running tests in nix developfirst I got error about this-error crate using nightly feature provide_any, but after switching to nightly in rust-toolchain.toml I got another error in gen_llvm crate about let ... else statement being unstable. I tried adding the #![feature(let_else)] but I'm not sure where to put it.
Folkert de Vries (Mar 28 2023 at 12:16):I suspect your rust version is old
Folkert de Vries (Mar 28 2023 at 12:17):hmm actually, maybe the compiler rust version is old? @Anton the toolchain toml says it's 1.65 still. rust is on 1.68 at this point. maybe we can upgrade again?
Folkert de Vries (Mar 28 2023 at 12:18):to anwer the question: the roc compiler uses the stable toolchain
Folkert de Vries (Mar 28 2023 at 12:19):and based on the rust-toolchain.toml it uses rust 1.65
Folkert de Vries (Mar 28 2023 at 12:19):you can run e.g. cargo --version to see which version you actually have
Anton (Mar 28 2023 at 12:19):I'll make a note to upgrade.
But with nix you can basically not use the wrong rust version, so I think something is off
Folkert de Vries (Mar 28 2023 at 12:20):well based on the errors, the compiler used is too old for the code that it is compiling
Anton (Mar 28 2023 at 12:20):@ziutech can you tell me what OS you are on and the sequence of commands you executed?
Anton (Mar 28 2023 at 12:21):Are you using the main branch without any changes?
Chris (Mar 28 2023 at 12:25):I'm on linux
I'm directly on main, without any changes
I updated my fork, pulled changes, then run nix develop and cargo run
Anton (Mar 28 2023 at 12:27):While in a nix shell (=after having executed nix develop), can you do a cargo clean, followed by cargo run repl?
Anton (Mar 28 2023 at 12:27):I suspect that you have some rust crates in play from once executing cargo without nix.
Chris (Mar 28 2023 at 12:35):Okay, now everything works, thank you
Anton (Mar 28 2023 at 12:44):Several people have encountered this issue. I wonder if we could alias cargo in the flake to quickly inspect some metadata before running so that we can provide a nice error message when crates compiled outside of nix are detected :thinking:
Last updated: Jul 26 2025 at 12:14 UTC