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What does underscore mean in this type expression?
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Date: -- (:)
From: Richard Jones <rich@a...>
Subject: What does underscore mean in this type expression?
I'm seeing this type error.  Notice the difference is a lowly
underscore character.

  The implementation libvirt.ml does not match the interface libvirt.cmi:
  Values do not match:
    val get_domains :
      (_[> `R ] as 'a) Connect.t ->
      ?want_info:bool ->
      Domain.list_flag list -> 'a Domain.t list * Domain.info list
  is not included in
    val get_domains :
      ([> `R ] as 'a) Connect.t ->
      ?want_info:bool ->
      Domain.list_flag list -> 'a Domain.t list * Domain.info list

This syntax doesn't appear to be documented in the manual (unless it's
related to '_a).  What does it mean?

I can supply some reproducer code if needed, but the code is rather
long at the moment.

Rich.

-- 
Richard Jones
Red Hat