Type from local module would escape its scope? - fa.caml

Message from discussion Type from local module would escape its scope?

Jean-Marie Gaillourdet

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More options Jul 3 2006, 9:58 am

Newsgroups: fa.caml

From: Jean-Marie Gaillourdet <j...@gaillourdet.net>

Date: Mon, 03 Jul 2006 13:58:28 UTC

Local: Mon, Jul 3 2006 9:58 am

Subject: Re: [Caml-list] Type from local module would escape its scope?

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Hello,

On 03.07.2006, at 15:19, Bruno De Fraine wrote:

> While the following is rejected:

> let foo (ignore: 'a -> unit) =
> let module Foo : FOO =
> struct
> type t = int
> let value = 1
> end in
> ignore Foo.value
> ;;

> With an error on the expression "Foo.value" stating that "The type
> constructor Foo.t would escape its scope". Reading about the
> typical case for this error message in http://caml.inria.fr/pub/ml-
> archives/caml-list/2002/10/0cf087feab3ef8dc5ccba5a8592472fb.en.html
> didn't really help me. Why does it make a difference whether ignore
> is an argument?

Let us extend your example with the following code:

> let foo (ignore: 'a -> unit) =
> let module Foo : FOO =
> struct
> type t = int
> let value = 1
> end in
> ignore Foo.value
> ;;

let bar (ignore: 'b -> unit) =
let module Foo : FOO =
struct
type t = float
let value = 1.0
end in
ignore Foo.value

let baz () =
let x = ignore in begin
foo x;
bar x
end

Which type should x have?

Best Regards,
Jean-Marie

PS: didn't compile that code

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