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This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds 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

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds I’ve been thinking a wild thought lately: we should deprecate panic=unwind. Most production users I know either already run with panic=abort or use unwinding in a very limited fashion, basically just to run to cleanup, not to truly recover. Removing unwinding from most case meanwhile h

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds 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

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds You’ve probably heard that the Rust type checker can be a great “co-pilot”, helping you to avoid subtle bugs that would have been a royal pain in the !@#!$! to debug. This is truly awesome! But what you may not realize is how it feels in the moment when this happens. The answer typical

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds In my #rust2020 blog post, I mentioned rather off-handedly that I think the time has come for us to talk about forming a Rust foundation. I wanted to come back to this topic and talk in more detail about what I think a Rust foundation might look like. And, since I don’t claim to have t

When users invoke this run function from JS, it acts just like a JavaScript asynchronous function, which means that it returns a JS promise. This is possible because wasm-bindgen includes the ability to interconvert between JS and Rust promises. You can see this at play also within the run function, which invokes fetch and then converts the result into a Rust future: Note the JsFuture::from call i

What’s interesting about this code is how uninteresting it is – it basically just does what you expect, and didn’t require any special action to please the borrow checker3. But the borrowing patterns are actually sort of complex: it starts as we enter the match (match &message) and continues into the match arm. On the else branch of the match, the borrow is still in use (in the form of the data va

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other 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

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds Ever since the Rust All Hands, I’ve been experimenting with an alternative formulation of the Rust borrow checker. The goal is to find a formulation that overcomes some shortcomings of the current proposal while hopefully also being faster to compute. I have implemented a prototype for

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other So aturon wrote this beautiful post about what a good week it has been. In there, they wrote: Breakthrough #2: @nikomatsakis had a eureka moment and figured out a path to make specialization sound

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other I’ve been thinking a lot about persistent collections lately and in particular how they relate to Rust, and I wanted to write up some of my observations.1 What is a persistent collection?Tradition

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other I’ve been hard at work the last month or so on trying to complete the non-lexical lifetimes RFC. I’m pretty excited about how it’s shaping up. I wanted to write a kind of “meta” blog post talking

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds This last week we had the rustc compiler team design sprint. This was our second rustc compiler team sprint; the first one (last year) we simply worked on pushing various projects over the finish line (for example, in an epic effort, arielb1 completed dynamic drop during that sprint).

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other Over the last year or two (man, it’s scary how time flies), I’ve been doing quite a lot of thinking about Rust’s trait system. I’ve been looking for a way to correct a number of flaws and shortcom

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds Associated type constructors, part 3: What higher-kinded types might look like This post is a continuation of my posts discussing the topic of associated type constructors (ATC) and higher-kinded types (HKT): The first post focused on introducing the basic idea of ATC, as well as intro

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other So for the end of last week, I was at Rust Belt Rust. This was awesome. And not only because the speakers and attendees at Rust Belt Rust were awesome, though they were. But also because it gave a

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds 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

Of course, part of making parallelism easy is making it safe. Rayon guarantees you that using Rayon APIs will not introduce data races. This blog post explains how Rayon works. It starts by describing the core Rayon primitive (join) and explains how that is implemented. I look in particular at how many of Rust’s features come together to let us implement join with very low runtime overhead and wit

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds One priority for Rust after 1.0 is going to be incorporating some kind of support for “efficient inheritance” or “virtual structs”. In order to motivate and explain this design, I am writing a series of blog posts examining how Rust’s current abstractions compare with those found in ot

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds After reading nrc’s blog post about graphs, I felt inspired to write up an alternative way to code graphs in Rust, based on vectors and indicates. This encoding has certain advantages over using Rc and RefCell; in particular, I think it’s a closer fit to Rust’s ownership model. (Of cou

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds 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 th

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feedsSelected posts: The borrow checker withinEmpathy in open source: be gentle with each other I’ve been thinking about an alternative way to factor the PJS API. Until now, we’ve had these methods like mapPar(), filterPar() and so forth. They work mostly like their sequential namesakes but

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds Here is the current state of my thinking with respect to value types and value objects. Some of you may have seen Brendan’s slides where he discusses value objects. This post is about the same topic, but it is focused on just the initial part of the work – what it means to be a value o

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds I believe I have come to the point where I am ready to make a final proposal for DST. Ironically, this proposal is quite similar to where I started, but somewhat more expansive. It seems to be one of those unusual cases where supporting more features actually makes things easier. Thank

This blog is where I post up various half-baked ideas that I have. All PostsCategoriesGitHubTwitterRSS/Atom feeds There is currently some ongoing effort to implement the proposed JavaScript SIMD API in Firefox. The basic idea of the API is to introduce explicit vector value types called float32x4 and int32x4. These types fit into the typed objects hierarchy, so you can create arrays of them, embed