[perl #124149] [BUG] Declarative and procedural conjunctions in regex don't remember the keys of positional captures

[via RT]

# New Ticket Created by  Pepe Schwarz 
# Please include the string:  [perl #124149]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=124149 >


19:43 < psch> m: say ("a" ~~ /(.) | ./); say ("a" ~~ /(.) & ./)
19:43 <+camelia> rakudo-moar 5778e8: OUTPUT«｢a｣␤ 0 => ｢a｣␤｢a｣␤  => ｢a｣␤»
19:43 < psch> the mysterious case of the disappearing 0
19:43 < FROGGS> O.o
19:44 < Mouq> m: say ("a" ~~ /. & (.)/)
[...]
19:44 <+camelia> rakudo-moar 5778e8: OUTPUT«｢a｣␤  => ｢a｣␤»
19:44 < psch> nothing up my sleeve!
19:44 < FROGGS> m: say ("a" ~~ /(.) | ./); $/ := Nil; say ("a" ~~ /(.) & ./)
19:44 <+camelia> rakudo-moar 5778e8: OUTPUT«｢a｣␤ 0 => ｢a｣␤Cannot assign to an 
immutable value␤  in method ACCEPTS at src/gen/m-CORE.setting:16293␤  in block 
<unit> at /tmp/8whqFAKjvR:1␤␤»
[...]
19:44 < FROGGS> m: say ("a" ~~ /(.) | ./); $/ = Nil; say ("a" ~~ /(.) & ./)
19:44 <+camelia> rakudo-moar 5778e8: OUTPUT«｢a｣␤ 0 => ｢a｣␤｢a｣␤  => ｢a｣␤»
[...]
19:45 < psch> that kind of threw a wrench in my attempt to make .caps more 
reliable
[...]
19:45 < jnthn> psch: At a guess, the code generated for the & stuff could be 
mis-managing the cstack
19:45 < jnthn> I forget how on earth & is compiled, but it does involve some 
trickery with the marks.
[...]
19:46 < psch> jnthn: okay.  the regex match code isn't for me, though.  i'll RT 
it

19:54 <psch> m: say "a" ~~ /(.) && ./
19:54 <camelia> rakudo-moar 5778e8: OUTPUT«｢a｣␤  => ｢a｣␤»