How to use .cargo/config.toml file with both stable and nightly rust toolchain?

Question

I have installed both nightly and stable rust toolchains and make some -Z ... compile flags for nightly, but the stable rust can't recognize it and stops compiling; is there a way or a cargo directive to conditionally switch between nightly/stable rust compiler.

In .cargo/config.toml file

[build]
rustflags = [
"-C...",

"-Z...",
]

For nightly rust read -Z and -C flags, for stable rust only read -C or ignore -Z completely. So that, we can use cargo +stable/+nightly build without modify config.toml file every time.

Thanks Ruster ~

Answer 1

I don't think it's possible to specify rustc unstable feature inside config.toml but you can specify cargo unstable feature. It could be nice to have.

You could create a "nightly" directory:

cd my_rust_project
mkdir my_nightly_project
cd my_nightly_project
rustup override set nightly

Then using merge feature of config file of cargo you create you can override the global config using a my_nightly_project/.cargo/config.toml file.

Consider using alias instead.