Which OCaml features exist in Rust but not Haskell? The trait system looks very similar to Haskell typeclasses, but I'm not aware of any novel OCaml influence on the language.
I'm not convinced the implementation language of the compiler counts as a feature of the Rust language. If the argument is that Rust wouldn't have been invented without the original author wanting a 'systems OCaml' then fine. But it's possible Rust would still look similar to how it does now in a counterfactual world where the original inspiration was Haskell rather than OCaml, but removing the Haskell influence from Rust as it is now would result in something quite different.
Additionally, unlike some languages that are formally specified before turning to implementation, Rust has subscribed to design-by-implementation. The implementation is the language.
That just means the semantics of the language are defined by whatever the default implementation does. It's a big stretch to conclude that means Rust 'was' OCaml in some sense when the compiler was written with it. Especially now the Rust compiler is written in Rust itself.
