From firefish6000@gmail.com

*Description​:*
Longest alternation seems to only evaluate the first nested alternation of
its right side arguments.
That is, if the first regex of an alternation <||> following longest
alternation <|> fails, and the regex preceding the longest alternation
succeeds, the longest alternation uses the preceding/ left side match
rather than evaluating the rest of the right side alternation which could
have a potentially longer match.

*Example 1​:*
'succeed'.match(/ suc | [ fail || succeed ]/).say;

Returns​:
｢suc｣

Expected​:
｢succeed｣

*Example 2​:*
grammar TEST {
  regex NestedAlternation { fail || succeed }
  regex LongestAlternation { suc | <NestedAlternation> }
  regex TOP { <LongestAlternation> .* }
}
TEST.parse('succeed').say;

Returns​:
｢succeed｣
LongestAlternation => ｢suc｣

Expected​:
｢succeed｣
LongestAlternation => ｢succeed｣
  NestedAlternation => ｢succeed｣

Note if we remove the trailing '.*' in TOP, backtracking forces it to
evaluate the NestedAlternation and return the expected result. However,
backtracking back into the NestedAlternation should not be necessary.

*Example 3​:*
grammar TEST {
  token NestedAlternation { fail || succeed }
  token LongestAlternation { suc | <NestedAlternation> }
  token TOP { <LongestAlternation> }
}
TEST.parse('succeed').say;

Returns​:
Nil

Expected​:
｢succeed｣
LongestAlternation => ｢succeed｣
  NestedAlternation => ｢succeed｣

From @zoffixznet

Adding more content from OP (seems there's some possible delay/issue with RT emails) per https://irclog.perlgeek.de/perl6/2017-08-29#i_15086833

This is Rakudo version 2017.07-155-gc229022cb built on MoarVM version 2017.07-378-g5e94da03
implementing Perl 6.c.

Linux Kataomoi 4.13.0-rc6
CPU E3-1230 V2 @​ 3.30GHz GenuineIntel GNU/Linux
Also tested on IRC with Moar and Star

This is not specific to right side nested alternations.

Example 4​:
'succeed'.match(/ [fail || succeed] | suc /).say;
Result​:
｢suc｣
Expected​:
｢succeed｣

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

From @ronaldxs

Looks to me like possible dup of RT 130562 https://rt-archive.perl.org/perl6/Ticket/Display.html?id=130562

See also doc issue​: Raku/doc#1141

From @ronaldxs

Closing on request​: https://irclog.perlgeek.de/perl6/2017-08-29#i_15087239

I have never closed anybody else's ticket before so let me know if I am doing anything wrong.

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

From @TimToady

Yes, as noted above, this is a dup of rejected ('better docs needed', really) ticket #​130562.

From firefish6000@gmail.com

This is Rakudo version 2017.07-155-gc229022cb built on MoarVM version
2017.07-378-g5e94da03
implementing Perl 6.c.

Linux Kataomoi 4.13.0-rc6
CPU E3-1230 V2 @​ 3.30GHz GenuineIntel GNU/Linux

Also tested on IRC with Moar and Star

On Tue, Aug 29, 2017 at 1​:22 PM, perl6 via RT <perl6-bugs-followup@​perl.org>
wrote​:

Greetings,

This message has been automatically generated in response to the
creation of a trouble ticket regarding​:
"[REGEX] Longest Alternation followed by an Alternation fails",
a summary of which appears below.

There is no need to reply to this message right now. Your ticket has been
assigned an ID of [perl #​131991].

Please include the string​:

     \[perl #​131991\]

in the subject line of all future correspondence about this issue. To do
so,
you may reply to this message.

                    Thank you,
                    perl6\-bugs\-followup@​perl\.org

-------------------------------------------------------------------------
*Description​:*
Longest alternation seems to only evaluate the first nested alternation of
its right side arguments.
That is, if the first regex of an alternation <||> following longest
alternation <|> fails, and the regex preceding the longest alternation
succeeds, the longest alternation uses the preceding/ left side match
rather than evaluating the rest of the right side alternation which could
have a potentially longer match.

*Example 1​:*
'succeed'.match(/ suc | [ fail || succeed ]/).say;

Returns​:
｢suc｣

Expected​:
｢succeed｣

*Example 2​:*
grammar TEST {
regex NestedAlternation { fail || succeed }
regex LongestAlternation { suc | <NestedAlternation> }
regex TOP { <LongestAlternation> .* }
}
TEST.parse('succeed').say;

Returns​:
｢succeed｣
LongestAlternation => ｢suc｣

Expected​:
｢succeed｣
LongestAlternation => ｢succeed｣
NestedAlternation => ｢succeed｣

Note if we remove the trailing '.*' in TOP, backtracking forces it to
evaluate the NestedAlternation and return the expected result. However,
backtracking back into the NestedAlternation should not be necessary.

*Example 3​:*
grammar TEST {
token NestedAlternation { fail || succeed }
token LongestAlternation { suc | <NestedAlternation> }
token TOP { <LongestAlternation> }
}
TEST.parse('succeed').say;

Returns​:
Nil

Expected​:
｢succeed｣
LongestAlternation => ｢succeed｣
NestedAlternation => ｢succeed｣

From firefish6000@gmail.com

This is Rakudo version 2017.07-155-gc229022cb built on MoarVM version
2017.07-378-g5e94da03
implementing Perl 6.c.

Linux Kataomoi 4.13.0-rc6
CPU E3-1230 V2 @​ 3.30GHz GenuineIntel GNU/Linux

Also tested on IRC with Moar and Star
This is not specific to right side nested alternations.

*Example 4​:*
'succeed'.match(/ [fail || succeed] | suc /).say;
Result​:
｢suc｣
Expected​:
｢succeed｣