From @masak

<masak> :T allows only type objects, not just any undefined thing.
<masak> :U allows undefined things.
<masak> r​: multi foo(Int​:U) { say "undefined" }; multi foo(Int​:D) {
say "defined" }; foo 42; foo 42 but role { method defined { False } }
<p6eval> rakudo 038a3c​: OUTPUT«defined␤defined␤»
<masak> apparently that wasn't undefined enough :)
<sirrobert> heh
<quietfanatic> Rakudo might be cheating.
<Tene> r​: multi foo(Int​:U) { say "undefined" }; multi foo(Int​:D) { say
"defined" }; foo 42; foo Int
<p6eval> rakudo 038a3c​: OUTPUT«defined␤undefined␤»
<jnthn> :U is currently taken to mean "type object"
<masak> huh.
<jnthn> Just after I implemented that lot, the spec got changed. :/
* masak submits rakudobug
<jnthn> I'm hoping if I ignore the spec change enough it may change back :P

From @ShimmerFairy

This is actually according to spec. The :U and :D smileys check on objects via .DEFINITE, not .defined. So the behavior presented is as it should be.

Additionally, the :T smiley was never implemented in rakudo, and :U/​:D have come to distinguish type objects from object instances. The only theoretical difference between :T and :U as spec'd is not applicable anymore. (​:U was supposed to let Failure objects through where :T didn't, but in today's Perl 6 Failure objects are never accepted by type constraints any differently than all other types.) So the :T smiley has been removed from the spec.

For both reasons, this ticket should be rejected.

The RT System itself - Status changed from 'new' to 'open'

From @labster

<jnthn> I'm hoping if I ignore the spec change enough it may change back :P

Wish granted. Rejecting ticket.

On Fri Aug 14 00​:03​:08 2015, lue wrote​:

This is actually according to spec. The :U and :D smileys check on
objects via .DEFINITE, not .defined. So the behavior presented is as
it should be.

Additionally, the :T smiley was never implemented in rakudo, and :U/​:D
have come to distinguish type objects from object instances. The only
theoretical difference between :T and :U as spec'd is not applicable
anymore. (​:U was supposed to let Failure objects through where :T
didn't, but in today's Perl 6 Failure objects are never accepted by
type constraints any differently than all other types.) So the :T
smiley has been removed from the spec.

For both reasons, this ticket should be rejected.

@labster - Status changed from 'open' to 'rejected'