Only check the active toolchain if rustup is installed

[ntrinquier]

No description provided.

[j-baker]

I don't think this is quite right. I expect the right solution for this problem is to do something like run rustc --version and check that the version string is a nightly release, if you want to ensure that everything runs with nightly.

It also still checks that all compilation occurs with nightly if one does have rustup, I think? Whereas I think the +nightly will dynamically enable it for the command, so we only really want to check if nightly is installed, not that it's active.

If one were checkign with rustup, I'd expect that the right way would be to list the installed toolchains and check that nightly is in the list?

[ntrinquier]

I don't think this is quite right. I expect the right solution for this problem is to do something like run rustc --version and check that the version string is a nightly release?

It also still checks that all compilation occurs with nightly, I think?

This only affects cargo fmt, not the compilation (and now that we made it opt-out, only the user specified nightly=True)

[j-baker]

Won't rustup show active-toolchain return nightly if rustc is going to compile with nightly? Or am I misunderstanding what that command returns?

[ntrinquier]

I think the +nightly will dynamically enable it for the command, so we only really want to check if nightly is installed, not that it's active.

yeah that's fair