Or write it in a language where you don't even have to think about it.

(you have to maintain separate toolchain and exports in Rust, to achieve this, and complex types cannot be easily exported/imported - it is subject to limitations of C ABI, and FFI is not free either, even when as cheap as it gets - .NET has that with P/Invoke yet still it is a deoptimization in data-intensive algorithms, which benefit from being rewritten in C#/F#)