[Caml-list] tpyping question

[skaller <skaller@ozemail.com.au>]

type x = [`A | `B of int | `V of float];;
let g (a:x) = a;;
let f a = match a with
| `A -> g a
(* | `B _ *) | _ -> g a;;

Compiles fine, but gives an error if the comments are
removed.

File "xx.ml", line 4, characters 10-11:
This expression has type [< `A | `B of 'a ] but is here used with type
  x = [ `A | `B of int | `V of float ]
The first variant type does not allow tag(s) `V

I can fix this with a coercion/annotation:

| (`A:x) -> g a

but that's a bit messy. Of course an annotation on the
argument doesn't work (since such annotations are only
consulted *after* the body type is infered).

Is there a better way to do this?


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