[MLton] mlb files and the ML Kit

[Stephen Weeks]

> We could perhaps issue a warning if a file (is mentioned multiple
> times). In most cases, I belive it would be a mistake, 

A warning sounds reasonable, at least if the mention is twice in the
same mlb file.  Twice in different mlb files I'm not so sure.

> but perhaps the programmer would use the feature to write poor-man
> functors.

The thought had occurred to me as well.

> I don't think that is enough. Consider the mlb-file:
> 
>  bad.mlb:
>   A.sml B.sml C.sml D.sml B.sml E.sml
> 
> and the content map
> 
>  A.sml:  type t0 = int
>  B.sml:  datatype t = T of t  
>  C.sml:  val a = T 4
>  D.sml:  type t0 = bool
>  E.sml:  val _ = case a of T b => print (Bool.toString b)
> 
> Here the ``type name'' "B.sml-t" is not sufficient to ensure type
> soundness... But I think I can use the position in the mlb-file to get
> things to work.

That makes sense.