From: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
To: Hongbo Zhang <bobzhang1988@gmail.com>
Cc: caml-list <caml-list@yquem.inria.fr>
Subject: Re: [Caml-list] First Class modules -A bug in 4.00?
Date: Fri, 8 Jun 2012 12:22:17 +0900 [thread overview]
Message-ID: <8D5E880B-79AC-45E1-B866-B83C3D725E36@math.nagoya-u.ac.jp> (raw)
In-Reply-To: <4FD164E2.4050807@gmail.com>
On 2012/06/08, at 11:35, Hongbo Zhang wrote:
> Hi, List
> I am not sure this is a bug or not?
>
> Below is a contrived example:
> ------------------
> module type S = sig
> type t=int
> module X : sig type u end
> end
>
> let f ( module X : S) (y:X.X.u) =
> 3
> --------------------
> Error: This pattern matches values of type X.X.u
> but a pattern was expected which matches values of type X.X.u
> The type constructor X.X.u would escape its scope
> -- Thanks
Definitely, this is not a bug.
Type X.X.u is abstract, and showing it outside (as by taking an argument
of that type) would be meaningless.
What you might have meant is:
let f (type a) (module X : S with type X.u = a) (y : X.X.u) = 3
This is typable (but I'm not sure it means anything...)
Jacques Garrigue
next prev parent reply other threads:[~2012-06-08 3:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-08 2:35 Hongbo Zhang
2012-06-08 3:22 ` Jacques Garrigue [this message]
2012-06-08 15:25 ` bob zhang
2012-06-08 15:29 ` bob zhang
2012-06-08 20:25 ` Milan Stanojević
2012-06-10 9:27 ` Jacques Garrigue
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