Type signatures are optional in Haskell, but in OCaml you can even specify partial signatures (e.g. just one parameter).
Maybe return types are more valuable to annotate? I can often guess params based on the name, but I have to read the function body for the result.
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Playing with optional type signatures in Python, I realise that the return type is the most important to me.
I'd much rather have a function with only a return type instead of a function with only parameter types. It's often quick to add too.
I really like pattern matching in Rust, but I find myself using it less and less.
`if let` and `let ... else` require substantially less indentation, and I often use them for Option values.
I don't miss this syntactic sugar in OCaml though. Maybe it's just because OCaml has a 2 space indent, unlike Rust's 4 space indent?
`init` feels like an unhelpful name in OO. It doesn't give you an initial value, it initialises the instance that has already been created. Developers are often surprised that init doesn't return the instance, because they have a strong association with `new Foo()`.
Perhaps `finish` would have been a less confusing name?