Comment by skybrian
20 hours ago
Being first isn't necessarily good if you get it wrong, though. Laziness by default and Hindley-Milner type inference seem like mistakes that simply aren't going to get cleaned up. Other languages make their own mistakes too.
What's wrong with Hindley-Milner?
Leaving out types in public API's makes type errors hard to understand. Types should be declared in the API and bidirectional type inference used in the implementation.
https://jimmyhmiller.com/easiest-way-to-build-type-checker
Eh. This causes some problems for rust. Right now you can have a function return impl Trait instead of a concrete type. Very handy - and essentially required by async functions.
But the language also requires that types have names in lots of places. For example, you can't store an 'impl Trait' in a struct. You can't make a type alias of an impl Trait. And so on. As a result, async rust can only interact with a butchered subset of the language. (You can work around this with Box<dyn Future<...>> but performance suffers.)
There's a proposal[1] to fix this. But the proposal has been under discussion for (checks watch) 7 years now. Until this lands, async remains a second class citizen in rust.
This entire problem stems from rust's early decision to requiring concrete types at interface boundaries.
https://github.com/rust-lang/rust/issues/63063