Type Variables in Native Toplevel

[NathanReb]

The native toplevel does not retain type var names as the bytecode toplevel does. When a type with type parameters is defined in a native toplevel session, with those parameters explicitly named, future evaluation may not retain this name and use the regular 'a, 'b, etc. instead.

Here's an example, taken from ocaml-jit's test suite:

# module A : sig 
    type ('foo, 'bar) t

    val get_foo : ('foo, _) t -> 'foo option
  end = struct
    type ('foo, 'bar) t =
      | Foo of 'foo
      | Bar of 'bar

    let get_foo = function
      | Foo foo -> Some foo
      | Bar _ -> None
  end
  ;;
module A :
  sig type ('foo, 'bar) t val get_foo : ('foo, 'a) t -> 'foo option end
# A.get_foo;;
- : ('foo, 'a) A.t -> 'foo option = <fun>

This is what you get in a bytecode toplevel, the 'foo type variable is preserved in the toplevel evaluation of A.get_foo. Running the same phrases in a native toplevel would get you:

- : ('a, 'b) A.t -> 'a option = <fun>

This has been fixed in ocaml-flambda/flambda-backend#188.

The upstream patch is awaiting review here ocaml/ocaml#10712.

[dra27]

This is fixed in 4.14!

[NathanReb]

Wonderful, thanks for taking care of this!