crane/docs/faq/invalid-metadata-files-for-crate.md

## `found invalid metadata files for crate` errors

This error can occur when mixing components from two different Rust toolchains,
for example, using `clippy` with artifacts produced from a different cargo
version. Check the configuration for specifying the exact Rust toolchain to be
used in the build:

```nix
let
  rustToolchain = ...;
in
# Incorrect usage, missing `clippy` override!
#(crane.mkLib pkgs).overrideScope (final: prev: {
#  rustc = rustToolchain;
#  cargo = rustToolchain;
#  rustfmt = rustToolchain;
#});

# Correct usage (`overrideToolchain` handles the details for us)
(crane.mkLib pkgs).overrideToolchain rustToolchain
```