use_msrv() sets the minimum supported rust version for your R package.
Details
The minimum supported rust version (MSRV) is determined by the
SystemRequirements field in a package's DESCRIPTION file. For example, to
set the MSRV to 1.67.0, the SystemRequirements must have
rustc >= 1.67.0.
By default, there is no MSRV set. However, some crates have features that depend on a minimum version of Rust. As of this writing the version of Rust on CRAN's Fedora machine's is 1.69. If you require a version of Rust that is greater than that, you must set it in your DESCRIPTION file.
It is also important to note that if CRAN's machines do not meet the specified MSRV, they will not be able to build a binary of your package. As a consequence, if users try to install the package they will be required to have Rust installed as well.
To determine the MSRV of your R package, we recommend installing the
cargo-msrv cli. You can do so by running cargo install cargo-msrv. To
determine your MSRV, set your working directory to src/rust then run
cargo msrv. Note that this may take a while.
For more details, please see cargo-msrv.