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This post lays out a 4-part roadmap for the borrow checker that I call “the borrow checker within”. These changes are meant to help Rust become a better version of itself, enabling patterns of code which feel like they fit within Rust’s spirit , but run afoul of the letter of its law . I feel fairly comfortable with…
While on vacation, I’ve been working on an alternate type inference scheme for rustc. (Actually, I got it 99% working on the plane, and have been slowly poking at it ever since.) This scheme simplifies the code of the type inferencer dramatically and (I think) helps to meet our intutions (as I will explain). It is…
One of the long-standing issues that we’ve been wrestling with in Rust is how to integrate the concept of an “uninhabited type” – that is, a type which has no values at all. Uninhabited types are useful to represent the “result” of some computation you know will never execute – for example, if you have to define an…
After reading boat’s excellent post on asynchronous destructors , I thought it might be a good idea to write some about async fn in traits. Support for async fn in traits is probably the single most common feature request that I hear about. It’s also one of the more complex topics. So I thought it’d be nice to do a…
Over the last few weeks, I’ve been devoting my free time to fleshing out the theory behind non-lexical lifetimes (NLL). I think I’ve arrived at a pretty good point and I plan to write various posts talking about it. Before getting into the details, though, I wanted to start out with a post that lays out roughly how…
I wanted to give an update on the status of the “async-await foundations” working group. This post aims to cover three things:
Around four years ago, when I had first decided to start at Mozilla research, I had planned to write an LR(1) parser generator. It seemed like a good way to get to know Rust. However, I found that newborns actually occupy somewhat more time than anticipated (read: I was lucky to squeeze in a shower), and hence that…
There has been a lot of discussion lately about Rust’s allocator story, and in particular our relationship to jemalloc. I’ve been trying to catch up, and I wanted to try and summarize my understanding and explain for others what is going on. I am trying to be as factually precise in this post as possible. If you see a…
One of the things people often complain about when doing Async Rust is cancellation. This has always been a bit confusing to me, because it seems to me that async cancellation should feel a lot like panics in practice, and people don’t complain about panics very often (though they do sometimes). This post is the start…
This blog post explores an alternative formulation of Rust’s type system that eschews lifetimes in favor of places . The TL;DR is that instead of having 'a represent a lifetime in the code, it can represent a set of loans , like shared(a.b.c) or mut(x) . If this sounds familiar, it should, it’s the basis for polonius…
In my previous post I outlined several cases that we would like to improve with Rust’s current borrow checker. This post discusses one possible scheme for solving those. The heart of the post is two key ideas:
On the rust-dev mailing list, someone pointed out another “BitC retrospective” post by Jonathon Shapiro concerning typeclasses . The Rust object system provides interesting solutions to some of the problems he raises. We also manage to combine traditional class-oriented OOP with Haskell’s type classes in a way that…
Rust currently has very strong support for concurrency in the form of actors which exchange messages and do not share memory. However, there are many tasks for which actors are not a good fit. The unbounded lifetime of actors means that they cannot safely access stack-allocated memory from another task, even if it is…