rust-overlay

Rust toolchains inside Nix, pinned to an exact version and identical on every machine. Nixpkgs ships its own rustc, but it moves with the channel, so pinning 1.79.0 or a specific nightly means fighting the package set. rust-overlay pulls the official Rust release binaries with hashes already committed, so evaluation needs no network. MIT, free.

Three lines in a flake: add the input, add the overlay, ask for rust-bin.stable.latest.default. Point fromRustupToolchainFile at an existing rust-toolchain.toml and your Nix shell matches what rustup gives everyone else. Extensions and cross-compilation targets are overrides on the same attribute. CI refreshes hashes daily, so new releases land within a day.

Solo Rust developers on NixOS: install it and stop thinking about toolchains. Small and medium teams: this is how every laptop and every CI runner lands on the identical compiler with no argument. Teams not already on Nix: this is not the reason to adopt it, and rustup with a committed rust-toolchain.toml does the same job.

The catch is everything around it. This solves one problem cleanly and inherits every other Nix problem: flake syntax, eval errors that read like stack traces, and a first build that pulls a lot down. Old nightlies get pruned after roughly a year, so anything pinned to an ancient one eventually stops evaluating.