bug#32463: 27.0.50; (logior -1) => 4611686018427387903

[Eli Zaretskii]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sat, 18 Aug 2018 11:48:11 -0700
> Cc: 32463@debbugs.gnu.org
> 
> It would be weird for lsh to act one way for negative bignums, and a 
> different 
> and incompatible way for negative fixnums. Instead, I suggest that we 
> deprecate 
> lsh, as it doesn't make sense any more now that integers have unbounded size. 

It is IMO absurd for us to deprecate a valid and useful operation just
because we added bignums.  If we cannot agree on its semantics for
bignums (which would surprise me), then it is better to make it not
work for bignums at all than deprecate it for fixnums.

> While we're deprecating it, we can make (lsh A B) signal an error if A is a 
> bignum and B is negative, since there's nothing we can do there that is 
> reasonable and is compatible with the fixnum behavior.

If that's the best we can do, fine.  But it doesn't require
deprecating lsh while we are at it.