[m3h]

The speed up numbers based on their testing:

    Codebase    | TypeScript 6 | TypeScript 7 | Speedup
    ------------|--------------|--------------|--------
    vscode      | 125.7s       | 10.6s        | 11.9x
    sentry      | 139.8s       | 15.7s        | 8.9x
    bluesky     | 24.3s        | 2.8s         | 8.7x
    playwright  | 12.8s        | 1.47s        | 8.7x
    tldraw      | 11.2s        | 1.46s        | 7.7x

Congratulations to the team for pulling off this feat while doing a responsible migration (looking at you, Bun).

Quick question: How does this affect downstream tools like tsdown and esbuild, which need to build the TypeScript codebase? Can I use TS 7 and current tsdown together?

[DanRosenwasser]

> How does this affect downstream tools like tsdown and esbuild, which need to build the TypeScript codebase?

esbuild doesn't rely on TypeScript at all, so there's no issue there.

With tsdown on the other hand, it depends on if you use --isolatedDeclarations. If not, you can install TypeScript 6 side-by-side (instructions for this are on the blog)

[paulddraper]

"How does this affect downstream tools"

> It’s worth calling out that workflows that use Vue, MDX, Astro, Svelte, and others will likely not yet be able to leverage TypeScript 7. Similarly, specialized type-checking within templates like Angular will also likely not use TypeScript 7. This is mainly because TypeScript 7 does not yet expose a stable programmatic API, and so tools (such as Volar) which embed TypeScript into their own compilers and language services can only currently rely on TypeScript 6.0. We expect this to be a point-in-time issue, as we are committed to providing a solution here. We will be actively working with the maintainers of these projects to ensure TypeScript 7 supports these workflows.

[hackerbrother]

Do you think Bun's migration was irresponsible?

[ricardobeat]

Not the op, but this TS migration started long before AI was able to help. It was done slowly and carefully, as a project supporting millions of users should. And the benefits are very clear.

Bun’s port was a vibe coding fever dream that happened from one day to the next, with much looser motive, and yet to be proven reliable.

[spartanatreyu]

> this TS migration started long before AI was able to help

Yes, but that doesn't mean it wasn't also "helped" along by AI.

See:

1. https://github.com/microsoft/typescript-go/pull/1387

2. https://github.com/microsoft/typescript-go/pull/2978

3. https://github.com/microsoft/typescript-go/pull/1138

4. etc...

Copilot is the "user" with the 2nd most commits (and the 15th and 19th too), and that's just what's been tracked in git.

---

The initial port was automated, then devs got in there, then LLMs got in there.

[docmars]

Bun's migration to Rust was nothing more than a marketing stunt to sell more Claude subs under the impression it can perform this kind of work at scale, assuming that most who were convinced by it wouldn't look under the hood at what really took place.

It has its merits as a proof of concept that could eventually be cleaned up and released properly later, but I can't see it any other way.

Too many see it as this miraculous one-shot and are using it as a blueprint to justify more layoffs and buzzword salad in their boisterous LinkedIn announcements about how they're "completely overhauling their strategy" in engineering. Hogwash.

[Tadpole9181]

Not sure I understand. Bun's changes are merged on the dev branch and available for use, no?

EDIT: Oh, look, blog post on the front page now.

https://bun.com/blog/bun-in-rust

> Bun v1.3.14 was the last version of Bun written in Zig. Bun v1.4.0 will be the first version of Bun written in Rust. It's available in canary now.

So, yes, it seems it was definitely more than a "marketing stunt" and it's broadly available and slated to be the production release soon.

[pjmlp]

The irony is that the blog post actually points out as pain points the reasons many of us assert languages like Zig are out of place in the 21st century.

A nice collection of heap-use-after-free crash, use-after-free crash, crash and out-of-bounds read, memory leak, double-free crash, race condition crash.

[andai]

Bun is infrastructure. Why would I want my infrastructure to be unstable? (By the way, 10,000 unsafe blocks last I checked, though the number is going down somewhat.)

[Tadpole9181]

I've never used bun on production for this very reason. But nevertheless, tens of thousands of people and businesses do.

And I'm not sure how you're responding to my comment. The parent said "this is a marketing stunt" derogatorily, as if it's slop that doesn't work. This is already the canary build, it's more stable than the current stable, and is actively in production products in wide use.

The parent is objectively wrong, whether or not I personally use Bun.

[moogly]

A minor version bump? Exciting times we live in.

[Tadpole9181]

What exactly is your complaint? It doesn't make any breaking changes. That's how semantic versioning works.

[golergka]

Marketing could of course be one of the main motivations, but it's not a "stunt". More like a marketing achievement, I guess? Stunt implies smoke and mirrors, and bun rewrite is quite real.

[jorisw]

Also it cost $165K in tokens

[Cthulhu_]

Probably cheaper than doing it by hand, however, that's the short term "port x to y" cost, the longer term cost (or benefit) is a lot harder to calculate.

[mindwok]

I don't think irresponsible is the right word, but it has drastically reduced Bun's appeal. All the tools we use have a brand to them, and Bun basically changed their brand overnight to "reckless" in my eyes.

[jitl]

bun has never been fit for production, at least not for load bearing business apps. it’s been haunted by segfault bug reports since the early days, and i personally hit at least one a week when im doing lots of bun stuff. im excited for bun with less segfaults

[brandensilva]

So reckless but needed.

[bastawhiz]

It's unknowable, because the PR is unreviewable. The Bun migration PR is larger than any model ever made can fit into context. You just have to pray that test coverage is sufficient to catch all of the possible errors, which it almost certainly isn't.

[jitl]

yeah but, the existing code was also full of bugs, so isn’t it all a wash in the end?

[bastawhiz]

The initial state has no bearing on whether the process was responsible or not. That's measuring along a different axis. If the bun rewrite lands and it breaks someone's app, that's bad no matter whether there's more or fewer bugs in the final state. The important metric in a rewrite of software that's used in production is stability.

[vlovich123]

inevitable: https://xkcd.com/1172/

[bastawhiz]

It's really not even close to being the same. In the best case, a bug means your app crashes on the new version. In the worst case, something more insidious happens like opening a security vulnerability (say, TLS isn't handled correctly or HTTP headers are mishandled in a way that allows SSRF or request smuggling) or a previously linear time operation is accidentally quadratic (leading to DoS).

[replygirl]

it's impossible to say, as v1.4 is in development and there has been no migration

[sdevonoes]

I would say it was a joke. Cannot take it seriously

[phplovesong]

Its was basically "hey claude, rewrite this"

[pjmlp]

The Typescript team is also using AI, even if not to the crazy Bun level.