Generators II: The Question Mark Problem

In July, I described a way to make pinning more ergonomic by integrating it more fully into the language. Last week, I develoepd that idea further with the notion of UnpinCell: a wrapper type that lets a user take an &pin mut UnpinCell and produce an &mut T, similar to how other cells let a user take a shared reference to the cell and produce a...

A variation on my previous design for pinned places has occurred to me that would be more consistent with Rust’s existing feature set. The most outlandish aspect of the previous design was the notion of “pinned fields,” which support pinned projection. This is quite different from how field projection normally works in Rust: if you have a mutable...

In the previous post, I described the goal of Rust’s Pin type and the history of how it came to exist. When we were initially developing this API in 2018, one of our explicit goals was the limit the number of changes we would make to Rust, because we wanted to ship a “minimum viable product” of async/await syntax as soon as possible. This meant...

The Pin type (and the concept of pinning in general) is a foundational building block on which the rest of the the Rust async ecosystem stands. Unfortunately, it has also been one of the least accessible and most misunderstood elements of async Rust. This post is meant to explain what Pin achieves, how it came to be, and what the current problem...

This post is meant as an explainer about how substructural type theory can be applied in programming language design. Terms like “substructural type theory” tend to scare and confuse programmers who don’t write Haskell on the weekends, so one thing programming language designers should do when thinking about how they will present their language...