From @bbkr

[13​:48] <bbkr> rakudo​: "" ~~ /{}*/; say "alive"
[13​:48] <p6eval> rakudo f8e959​: OUTPUT«(timeout)»

[13​:50] <bbkr> rakudo​: "" ~~ /{"a"}*/; say "alive"
[13​:50] <p6eval> rakudo f8e959​: OUTPUT«(timeout)»

[13​:49] <moritz> bbkr​: since {} doesn't return anything that can be matched
against, I'd argue it should complain "quantifiers follows nothing" or so
[13​:49] <moritz> or "can't quantify non-matching construct" or something
[13​:50] <moritz> IMHO it should be a parse error at compile time

From @FROGGS

Patches​:
Raku/nqp@41ab646099
rakudo/rakudo@de4b2b3a87

Tests​:
Raku/roast@95ee3272ab

Closing ticket.

@FROGGS - Status changed from 'new' to 'resolved'