From @LLFourn

15​:18 < llfourn_> m​: say (Str andthen .uc orelse "foo") # more golfed
15​:18 <+camelia> rakudo-moar 1c425f​: OUTPUT«-> ;; $_ is raw {
#`(Block|81391040) ... }␤»
15​:23 < llfourn_> m​: say (Str andthen .uc orelse "foo")("wee")
15​:23 <+camelia> rakudo-moar 1c425f​: OUTPUT«foo␤»

unless I totally missed what these are meant to do a Block is not what
should be returned from this expression.

From @zoffixznet

On Sun, 06 Nov 2016 20​:25​:50 -0800, lloyd.fourn@​gmail.com wrote​:

15​:18 < llfourn_> m​: say (Str andthen .uc orelse "foo") # more golfed
15​:18 <+camelia> rakudo-moar 1c425f​: OUTPUT«-> ;; $_ is raw {
#`(Block|81391040) ... }␤»
15​:23 < llfourn_> m​: say (Str andthen .uc orelse "foo")("wee")
15​:23 <+camelia> rakudo-moar 1c425f​: OUTPUT«foo␤»

unless I totally missed what these are meant to do a Block is not what
should be returned from this expression.

The issue is due to `andthen` (and `notandthen`) actually returning Empty instead of the advertized "first undefined value" and since Empty is a Slip, it causes an issue with `orelse`.

While the fix is trivial, it causes fallout with `with` operator and right now we're waiting for TimToady to chime in on how things should be done. IRC conversation​: https://irclog.perlgeek.de/perl6-dev/2016-11-09#i_13539174

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

From @LLFourn

Thanks for the update. As viki hinted at, isn't this a bug in itself
(andthen problems aside). Why does Empty as the first arg to orelse return
a block?

say (Empty orelse "foo")

-> ;; $_ is raw { #`(Block|140421623865904) ... }

Where as

say (Any orelse "foo")

returns the correct value.

On Thu, Nov 10, 2016 at 1​:51 AM Zoffix Znet via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Sun, 06 Nov 2016 20​:25​:50 -0800, lloyd.fourn@​gmail.com wrote​:

15​:18 < llfourn_> m​: say (Str andthen .uc orelse "foo") # more golfed
15​:18 <+camelia> rakudo-moar 1c425f​: OUTPUT«-> ;; $_ is raw {
#`(Block|81391040) ... }␤»
15​:23 < llfourn_> m​: say (Str andthen .uc orelse "foo")("wee")
15​:23 <+camelia> rakudo-moar 1c425f​: OUTPUT«foo␤»

unless I totally missed what these are meant to do a Block is not what
should be returned from this expression.

The issue is due to `andthen` (and `notandthen`) actually returning Empty
instead of the advertized "first undefined value" and since Empty is a
Slip, it causes an issue with `orelse`.

While the fix is trivial, it causes fallout with `with` operator and right
now we're waiting for TimToady to chime in on how things should be done.
IRC conversation​:
https://irclog.perlgeek.de/perl6-dev/2016-11-09#i_13539174

From @zoffixznet

Empty isn't passed as an arg. It's just an empty slip that gets flattened, so `orelse` ends up with a single block as the arg (the thunked "foo"), which gets returned.

I don't know whether it should be evaluated first.

On Wed, 09 Nov 2016 15​:52​:35 -0800, lloyd.fourn@​gmail.com wrote​:

Thanks for the update. As viki hinted at, isn't this a bug in itself
(andthen problems aside). Why does Empty as the first arg to orelse return
a block?

say (Empty orelse "foo")

-> ;; $_ is raw { #`(Block|140421623865904) ... }

Where as

say (Any orelse "foo")

returns the correct value.

On Thu, Nov 10, 2016 at 1​:51 AM Zoffix Znet via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Sun, 06 Nov 2016 20​:25​:50 -0800, lloyd.fourn@​gmail.com wrote​:

15​:18 < llfourn_> m​: say (Str andthen .uc orelse "foo") # more golfed
15​:18 <+camelia> rakudo-moar 1c425f​: OUTPUT«-> ;; $_ is raw {
#`(Block|81391040) ... }␤»
15​:23 < llfourn_> m​: say (Str andthen .uc orelse "foo")("wee")
15​:23 <+camelia> rakudo-moar 1c425f​: OUTPUT«foo␤»

unless I totally missed what these are meant to do a Block is not what
should be returned from this expression.

The issue is due to `andthen` (and `notandthen`) actually returning Empty
instead of the advertized "first undefined value" and since Empty is a
Slip, it causes an issue with `orelse`.

While the fix is trivial, it causes fallout with `with` operator and right
now we're waiting for TimToady to chime in on how things should be done.
IRC conversation​:
https://irclog.perlgeek.de/perl6-dev/2016-11-09#i_13539174

From @zoffixznet

Reply from TimToady​: https://irclog.perlgeek.de/perl6-dev/2016-11-11#i_13550043

I need to think a bit about this behaviour and maybe simply evaluating the thunk before returning it will fix the issues.

From @zoffixznet

On Sun, 06 Nov 2016 20​:25​:50 -0800, lloyd.fourn@​gmail.com wrote​:

15​:18 < llfourn_> m​: say (Str andthen .uc orelse "foo") # more golfed
15​:18 <+camelia> rakudo-moar 1c425f​: OUTPUT«-> ;; $_ is raw {
#`(Block|81391040) ... }␤»
15​:23 < llfourn_> m​: say (Str andthen .uc orelse "foo")("wee")
15​:23 <+camelia> rakudo-moar 1c425f​: OUTPUT«foo␤»

unless I totally missed what these are meant to do a Block is not what
should be returned from this expression.

Thank you for the report. This is now fixed.

Fix​: rakudo/rakudo@287af6a37e00ad
Test​: Raku/roast@8d6a6397e7

@zoffixznet - Status changed from 'open' to 'resolved'