From @AlexDaniel

Code​:
-> (Str() $a, Str() :$b) { say [$a, $b] }('abc'.match(/(.) $<b>=. ./))

¦«2015.12»​:
[a b]

¦«2016.06»​:
[a b]

¦«2016.12»​:
[a b]

¦«2017.06»​:
Cannot find method 'gist'​: no method cache and no .^find_method
  in block <unit> at /home/bisectable/git/whateverable/data/regressionable/15277191/snippet line 1
«exit code = 1»

¦«HEAD»​:
Cannot find method 'gist'​: no method cache and no .^find_method
  in block <unit> at /home/bisectable/git/whateverable/data/regressionable/15277191/snippet line 1
«exit code = 1»

Possible IRC discussion​: https://irclog.perlgeek.de/perl6-dev/2017-10-09#i_15277191

This was caused by â��uncurseâ�� branch merge​: https://gist.github.com/e908b4fcec227d6a66abd509c150c414

I'm just the messenger, I don't know what's going on in that code and if it should work at all. But the error message does not feel right at all.