It's the people that matter

Over the past two years, I've been involved with designing and implementing a new feature of rustc, called "externally implementable items". This is not a finished feature, though if you'd like you can try it on nightly already! This is the story of how externally implementable items were invented, implemented, and how some day they might be stabilized. I'm sure that is interesting to some of those who read this. That's not the main thing this blog post is about, though. Instead, I'm using it as an example, to show you how the Rust project operates. To show how many people are involved with a change, how they learn from each other, how I've learned so much from them myself. An example of how important _social_ interaction is to open source. Much more than writing the code itself. This is a written-out version of a talk I gave at Rust in Paris 2026.