I find TS philosophy of requiring input types and inferring return types (something I was initially quite sceptical about when Flow was adopting it) quite nice to work with in practice - the same could be applied to strict typing of errors ala Effect.js?
This does add the “complexity” of there being places (crate boundaries in Rust) where you want types explicitly defined (so to infer types in one crate doesn’t require typechecking all its dependencies). TS can generate these types, and really ought to be able to check invariants on them like “no implicit any”.
Rust of course has difference constraints and hails more from Haskell’s heritage where the declared return types can impact runtime behavior instead. I find this makes Rust code harder to read unfortunately, and would avoid it if I could in Rust (it’s hard given the ecosystem and stdlib).
I have some desire to make an RFC for limited cross-item inference within a single crate, but part of it wouldn't be needed with stabilized impl Trait in more positions. For public items I don't think the language will ever allow it, not only due to technical concerns (not wanting global inference causing compile times to explode) but also language design concerns (inferred return types would be a very big footgun around API stability for crate owners).
This already does work in TS, and there are some patterns besides Effect that simplify working with the return values.
Which brings me to my other big gripe with Rust (and Go): the need to declare structs makes it really unwieldy to return many values (resorting to tuples, which make code more error prone and again harder to read).
This does add the “complexity” of there being places (crate boundaries in Rust) where you want types explicitly defined (so to infer types in one crate doesn’t require typechecking all its dependencies). TS can generate these types, and really ought to be able to check invariants on them like “no implicit any”.
Rust of course has difference constraints and hails more from Haskell’s heritage where the declared return types can impact runtime behavior instead. I find this makes Rust code harder to read unfortunately, and would avoid it if I could in Rust (it’s hard given the ecosystem and stdlib).