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Type from local module would escape its scope?
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Date: -- (:)
From: Jean-Marie Gaillourdet <jm@g...>
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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