&gt; so I&#x27;m not convinced that this will be a problem in practice.<p>Historically, it&#x27;s been a massive problem. See my other post. Rust is already seeing IO-related fragmentation.<p>C, C++, Ruby, Python, etc. are all massively-fragmented ecosystems regarding IO, concurrency, (safe) parallelism. I don&#x27;t think we need to soil a great language (Rust) with these same mistakes.