In my previous post, I talked about programming language design, and try to discern some heuristics for what features should be added to a programming language, on my way to explaining why Rust should not include inheritance as a feature.

I’d like to expand more on that blog post now (so I guess it’s become a series?). Do I think Rust is perfect how it is? (No.) Are there features that I want in Rust that Rust currently does not have? (Absolutely yes.) In this post, I’d like to talk about some proposed additions to Rust, some recent, some very stale, and discuss my perspective on them.

Programming language design, like API design, and computer UX design (especially for technical tools like build systems and admin systems) is a difficult form of engineering, bridging computer science and cognitive science. Sometimes, it’s more art than science, because building systems that other technical workers will use comes with nearly infinite trade-offs and judgment calls.

The effort and quality matter too. Different programming languages have different strengths and weaknesses. Some programming languages are hard to use correctly, like C++. Some are easy to write, but hard to then read and maintain, like Perl. Some programming languages are great for one-off scripts where you’re the only user, like Python, and others enforce that you follow reliable engineering principles, like Rust.