Well, Rust's `?` was initially designed as a hardcoded/poor man's `Either` monad. They quote `?` as being one of the proposals they consider, so I think that co

Well, Rust's `?` was initially designed as a hardcoded/poor man's `Either` monad. They quote `?` as being one of the proposals they consider, so I think that counts? Source: I'm one of the people who designed it.