Re: [Caml-list] Numbered modules in error messages

[Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>]

On 2012/06/06, at 19:04, Dawid Toton wrote:

> Is it possible to make use of the numbers the compiler shows in the message below? What triggers this formatting?
> 
> Error: This expression has type O/3119.dexpr = O/3119.decor * O/3119.expr
>       but an expression was expected of type
>         O/1730.dexpr = O/1730.decor * O/1730.expr
>       Type O/3119.decor = O/3119.decor_fst * Static.t
>       is not compatible with type O/1730.decor = O/1730.decor_fst * Static.t
>       Type O/3119.decor_fst = Keep_defs.P.O.decor_fst
>       is not compatible with type O/1730.decor_fst = Indirloc.t
> 
> I'm asking this, because from time to time I deal with error messages like "type abc is not compatible with abc" with both abc being exactly the same strings. I'm wondering whether it is possible to force the compiler to say something more, to explain the difference between these types.

It is exactly what it does here:
it tells you that you have two versions of the module O, and that they
are incompatible because decor_fst has different definitions in these
two versions.

The output of numbers is triggered when the same identifier appears
twice for different entities.
So you should never have just "abc is not compatible with abc", as
the internal unique identifiers should be printed also.

Jacques Garrigue