[AnimalMuppet]

Well... how much of actual software is written using those type systems? Less than 1%? So such type systems might be able to prevent bugs, but in practice, they don't.

Why aren't they used? Probably existing code bases, inertia, and ignorance play a role. I suspect, though, that at least part of the problem is that most programmers find those type systems too hard to use. In that sense, the type systems aren't practical.

And if you're going to blame the programmers for that, well, if your plan for making programming better requires different programmers than the ones we have, your plan isn't very practical, either.

[hyperpape]

Today less than 1% of all software is written in null safe languages. But I believe Swift has non-nullable types, and it's the promoted language for a really big ecosystem. There's also Rust and Scala, but those have less of a captive audience. I do have high hopes for Rust, which also is data-race safe.

I think Java 8 and optionals show it doesn't have to be that hard, it's just that there's too much old code that relies on nulls for the Java ecosystem to ever be fully null safe.

Use-after-free is solved in a language without manual memory management, so that's actually quite common.

Programmers get comfortable with new ideas over time. Higher order functions and type inference used to be obscure concepts. Today they're par for the course. I don't know if we'll all use dependent types some day, but I think we'll keep getting more powerful types in mainstream languages for a while.

[swsieber]

Kotlin is plenty practical. It was born out of a desire for a safer yet practical language on the JVM (provides null safety at the type level). It is at least practical for it be getting gaining lots of traction.

Rust is another good example. It's not very ergonomic, but it is getting better every release.

I think how those two languages do will show whether type systems can me made practical for reducing wider classes of bugs. They seem practical and have the backing to help drive adoption.

[naasking]

> So such type systems might be able to prevent bugs, but in practice, they don't.

Rockets might be able to carry humans up to space, but in practice they don't because only a small set of humans actually get to go.

Isn't that a slightly absurd interpretation of "in practice"?

Why these languages aren't used may have absolutely nothing to do with their technical merits. It's a myth that technical merits is the only consideration for language popularity.