On Sat, Feb 03, 2007 at 10:57:50AM +0100, Gabriel Kerneis wrote:
> Le Fri, 2 Feb 2007 18:29:56 -0800, Bob Williams <a6b37331@telus.net> a
> ?crit :
> > My first impulse was to suggest that toplevel disallow the
> > redefinition of anything.  But Daniel has convinced me that reloading
> > an object file can be useful during development.  So how about this:
> > when toplevel redefines an exception, the exception's tag number
> > should not change.
> > 
> > Daniel mentioned a related problem, with similar pitfalls:
> > 
> > 	type t = C;;
> > 	... define function Foo using t ...
> > 	type t = D;;
> > 	... what should we do about Foo? ...
> > 
> > Foo is now clearly obsolete, as are any blocks on the heap that were
> > constructed by C.  What should be done here?
> 
> As you said, redefinition can be useful sometimes. But in most of the
> cases, it's a bug. So why not make the compiler issue a (possibly
> optional) warning on redefinitions ? 
> 
> Sincerely,
> -- 
> Gabriel Kerneis

I think that is a good idea.  Perhaps the warning should be issued
only when the new type differs from the old type.