User-defined "opIs"

[Adam D. Ruppe via Digitalmars-d]

On Wednesday, 24 September 2014 at 22:48:36 UTC, Meta wrote:
> Is this supposed to work, and if not, should an enhancement be 
> made to allow it?

It is not supposed to work - the docs don't list is as 
overridable (http://dlang.org/expression.html look for "Identity 
expressions") - and I don't think it should work either. Consider:

class A { opIs() }

if(a is null)

If that were rewritten into if(a.opIs(null))... and a were null, 
you'd have some trouble. Putting in an automatic null pre-check 
would start to complicate that is currently a simple operator.