[fhunt]

TS has by far the most advanced compile-time type system followed by Rust.

TS has the best and most responsive editor support (tsserver). I know that Rust's is much slower but IDK much more than that.

Re ecosystem and build system: TS' build system is not trivial but it's very flexible and has a bigger ecosystem.

[valenterry]

Idris and F* have a much much more advanced type system, compared to Typescript and Rust. But even if you deem these languages not "mainstream" enough, there is still e.g. Scala which has a typesystem that beats the one of Rust by far and also the one of Typescript, minus certain special cases where Typescript is really nice.

It is great to see though that even frontend-mainstream languages like Typescript start to get proper support for type-systems (especially considering that they had to do it on top of Javascript).

Very excited to see where we go with languages and I agree with you that TDD should now by default mean "type driven development". :)