Changing Rust version/channel about evcxr HOT 4 OPEN

BTW, it looks like evcxr is broken on nightly. Only noticed yesterday and just looking into it.

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I noticed there is this option:

:time_passes      Toggle printing of rustc pass times (requires nightly)

Which, as a consequence, switches to nightly. I am going with that workaround for now

from evcxr.

Tracking the time_passes flag, I found where the command is built:

        let mut command = std::process::Command::new("cargo");
        if self.time_passes {
            command.arg("+nightly");
        }
        command
            .arg("rustc")
            .arg("--message-format=json")
            .arg("--")
            .arg("-C")
            .arg("prefer-dynamic")
            .env_remove("CARGO_TARGET_DIR")
            .current_dir(self.crate_dir());
        if let Some(sccache) = &self.sccache {
            command.env("RUSTC_WRAPPER", sccache);
        }
        if self.time_passes {
            command.arg("-Ztime-passes");
        }

Doesn't look like there is a way to change the rustc toolchain. Am I wrong here?

from evcxr.

Sorry about the slow reply. That does seem like a useful thing to be able to change. For now the easiest way is probably to set the environment variable RUSTUP_TOOLCHAIN=nightly when running evcxr. e.g.:

RUSTUP_TOOLCHAIN=nightly evcxr

I guess eventually we could have a command to override from within evcxr.

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