Re: [Caml-list] OCaml release 4.02.0+beta1

[Andreas Rossberg <rossberg@mpi-sws.org>]

On 21.05.2014 14:13, Damien Doligez wrote:
> OCaml 4.02.0+beta1:
> -------------------

> - Allow opening a first-class module [...]  in the body of
>    an applicative functor if no types are created

Is that a good idea? It seems that one property you want from modules 
(second or first class) is that you can always extend them safely to a 
subtype (as a form of weakening). That property would be violated by 
such a typing rule, because extending a first-class module with a type 
might now unexpectedly break client code which unpacks it inside a 
functor, and relies on that functor being applicative.

(Of course, 'open' and 'include' already violate this property, but they 
stick out enough and are known to be brittle.)

/Andreas