I outlined some of the downsides in the comment, more in another comment of mine.

I thought about it even more and I think I can finally see the possibly true reason why people are developing these type of bundlers: The typescript projects that they have to work on are so huge that the typechecking is always going to be too slow so you don't want to deal with it, you rather typecheck only the file that you're currently working on and you don't care about the 15000 other files because you didn't touch them since checkout and the reasonable assumption is that they will probably still work same as tested by some other team that worked on them and committed them. However there is still one large implication: Your production build on the CI server must then at least be configured to execute both the typechecking process and then the bundling process. I still wonder though: if the typechecking is truly too slow then wouldn't it also be too slow for your iterative development. I guess if those other sections of the code are never referenced then maybe it will do okay and you don't get squiggly lines on all your imports because it won't recheck them? I have some doubts that the typescript type checker actually caches this type of work.

It is also strange because somehow every other language in the world doesn't have to separate type checking from compilation, it's only in the js world that we somehow ended up with such large amounts of code that people felt that they want that speed back from back when js could simply be loaded into the browser instantly with no compilation.

And on top of that: If Turbopack does such supposedly excellent caching now, why would this not help with a 15000 file project and let me also do typechecking in a cached way? Yes I really don't think that omitting typechecking is the way to go for development.

For typical workflows, I’m not looking for type errors on the CLI. I’m just running webpack in watch mode in the background, while I edit and get typescript errors in my editor.

This is how the majority of people write typescript, and there is only upside from splitting out bundling and type-checking for these people.

Typescript has an open bug to use multiple threads for compilation.

That's why it's slow. It's also not a big deal because of parallel type checkers.

> Yes I really don't think that omitting typechecking is the way to go for development.

You've not really given a reason why. Just a rant about how other languages are different.

It is you who is ranting at me with this small comment complaining about a lack of reasons while I've given many reasons now across multiple comments while you have called me a ranter with two dismissive lines.