[Fwd: Re: [Caml-list] Re: Improving OCaml's choice of type to display]

[Julien Signoles <Julien.Signoles@cea.fr>]

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Sorry, forgot the caml-list.

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From: Julien Signoles <Julien.Signoles@cea.fr>
To: Jun Furuse <jun.furuse@gmail.com>
Subject: Re: [Caml-list] Re: Improving OCaml's choice of type to display
Date: Mon, 12 Oct 2009 10:57:34 +0200
Message-ID: <4AD2EF7E.2080105@cea.fr>

Jun Furuse a écrit :
> I have not tested it well but it counts dots and should try to find
> the minimal one.
> 
> A problem I have found so far is that it prints something confusing, ex.
> 
> module M = struct type t end
> module N = struct type t end
> open M
> open N
> 
> let _ = ( 1 : M.t )
> 
>>> Error: This expression has type int but an expression was expected of type t    (which t ?!?!?)

 From the typing environment, it refers to N.t. Hence the type error 
message is not correct.

> If there are types M.t and N.t and the both of M and N are opened,
> these types are printed just "t". This can be avoided by testing the
> result name "t" against the current typing envrionment to see it
> really means the original type "M.t". This requires more coding but
> the weekend has ended in the far east already :-)   (It's 0:24 Monday
> now.)

One solution could be the following.

Let M.t the unique long type name to simplify and let P the longest 
prefix of M removed with the "do not print opened modules" rule.
After simplifying the long name M.t to (M - P).t (that is what your 
implementation does, if I well understood), add the shortest suffix S of 
M.t such that (M - P).S.t is visible in the current typing environment.

Don't know how hard is to implement such a solution in the caml compiler.

--
Julien