How to enable completions?

[giggio]

Completions are usually made available by rustup, which this package does not provide, IIRC.
How can we get completions when using Fenix?

Temporary workaround, add a derivation that just copies the existing derivation to the expected directory:
https://github.com/giggio/dotfiles/blob/448289156397e3d0aec40e2b7d22af13914ce2f0/config/home-manager/rust/cargo-completions.nix

[giggio]

After investigating it seems that completions are already in the package, at etc/bash_completion.d/cargo, it is just a matter of adding them to the derivation.

[AloisMisery]

I think something like

if [ -d $out/etc/bash_completion.d ]; then
  mkdir -p $out/share/bash-completion/completions
  cp $out/etc/bash_completion.d/* $out/share/bash-completion/completions
fi

needed to be added to installPhase in mk-toolchain.nix,

(sorry, im not familiar enough with git to make proper PR)