Is the rust-overlay flake input necessary?

[srid]

This flake has a 2nd input, rust-overlay:

nuenv/flake.nix

Lines 4 to 10 in 970bfd5

	inputs = {
	nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.1.*.tar.gz"; # Provides Nushell v0.87.1
	rust-overlay = {
	url = "github:oxalica/rust-overlay";
	inputs.nixpkgs.follows = "nixpkgs";
	};
	};

Which gets used as an overlay to pkgs:

nuenv/flake.nix

Lines 25 to 28 in 970bfd5

	rust-overlay.overlays.default
	(final: prev: {
	rustToolchain = prev.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
	})

Note that there's no ./rust-toolchain.toml file in the repo.

Is there a reason we need this?

---

Context: I'm considering using this flake in nixos-flake (for srid/nixos-unified#62), but the extra flake input seems to be a showstopper (as far as keeping flake.lock smaller goes).