Closures are the closest thing to closures Rust has.
Also, there's a lot of disagreement about exactly what the distinctions between `lambda`, `closure`, `anonymous function` and friends mean. The interpretation of `closure` I'm interested in is basically a bundle of code and data, which can be treated abstractly in a first class way. That could be something that appears as a lambda capturing variables in the text of your program or as an object in a more OO setting which, albeit more verbose for a single function, has a similar level of power of abstraction.
Either way, part of that power is being able to write code that can work with the interface (irrespective of the shape of the enclosed data), and do things like store differing implementations in lists/vecs etc. The only mechanism Rust provides to do that is trait objects.
I don't understand the issue (and I know very little of rust), but isn't `dyn impl Fn(A) -> B` exactly that type? Any language with first class function parameters and objects, but type erases them (unlike rust and c++) would implement them pretty much like the dyn impl above under the hood.
But dyn impl is a trait wrapped in an existential. There's no concrete type a -> b, only a trait for types that can be 'called.' So to pass an arbitrary function around in a record/struct you need to do the very thing the post is saying is an antipattern (in Haskell). So the argument doesn't really apply to Rust because there isn't a simpler more direct way to achieve the same thing.