Is there any tool that can detect the minimum version of Rustc my crate support? I want to publish my crate. In practice, it'd be better to notice the user the minimum version of Rustc.
But there's no way I can test compilers one by one, So is there any tool to do this?
Not really. In Tokio we have a CI job to verify that it still works on our MSRV (minimum supported rust version), and we emit a compiler error saying "Tokio doesn't support that version" when the version is older than that. But we don't try to check if Tokio becomes able to compile on something older, and we don't check versions between the MSRV and the newest stable Rust version.