* installing *source* package ‘fdars’ ...
** this is package ‘fdars’ version ‘0.3.3’
** package ‘fdars’ successfully unpacked and MD5 sums checked
** using staged installation
-----------------------------------------------------
ERROR: Rust toolchain not found.

This package requires the Rust programming language.
Please install Rust from: https://rustup.rs/

On most systems, you can install Rust with:
  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

After installation, restart your terminal and try again.
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ERROR: configuration failed for package ‘fdars’
* removing ‘/Users/ripley/R/packages/tests-devel/fdars.Rcheck/fdars’