Re: **DRAFT** issue CONSTANT-COLLAPSING

[Jeff Dalton <jeff%aiai.edinburgh.ac.uk@NSS.Cs.Ucl.AC.UK>]

> Rationale:
> 
> There is little reason why implementations should not be allowed to
> perform more general collapsing of structures, since the arguments
> against doing so also apply to collapsing of EQUAL structures, which
> is already permitted.

There's a problem with this rationale.  Arguments against individual
cases might also apply to EQUAL structures, but an argument that there
should be *some* non-coalescable structures is different.  I might
say, well, EQUAL sturctures is OK because I still have vectors, etc.
Removing all the alternatives requires more than arguments against
each one individually.

> Cost to users:
> 
> It is hard to imagine a program that would break under this proposal.

As I've said before, I think it's trivial to imagine a program that
would break.  Just think of one that assumes only EQUAL structures
will be collapsed.

-- Jeff