[perl #125987] [BUG] Unexpected "Useless use of emit in react"

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13:46   cdc     m: react { whenever supply { for "/etc/os-release".IO.lines { 
emit $_ }; done } { .say } }
13:46   GLRelia         rakudo-moar 17411e: OUTPUT«PRETTY_NAME="Debian 
GNU/Linux 8 (jessie)"␤Useless use of emit in react  in any  at 
/home/steve/sandbox/perl6/rakudo/install/shar​e/perl6/runtime/CORE.setting.moarvm:1␤Useless
 use of emit in react  in any  at 
/home/steve/sandbox/perl6/rakudo/install/shar…»

http://irclog.perlgeek.de/perl6/2015-09-04#i_11169035