[perl #83552] s[] is not recognized as illegal substitution with null pattern, but as a subroutine call

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# New Ticket Created by  Moritz Lenz 
# Please include the string:  [perl #83552]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=83552 >


08:49 < moritz_> rakudo: $_ = "foo"; s[] = 'bar'; .say
08:50 <+p6eval> rakudo 989883: OUTPUT«Could not find sub &s␤  in main 
program body at line 22:/tmp/b7_gMKxUFS␤»
08:51 < moritz_> rakudo: $_ = "foo"; s[f] = 'bar'; .say
08:51 <+p6eval> rakudo 989883: OUTPUT«baroo␤»
08:51 < moritz_> so it doesn't commit to the [
08:54 < TimToady> std: $_ = "foo"; s[] = 'bar'; .say
08:54 <+p6eval> std 625303c: OUTPUT«===SORRY!===␤Null pattern not 
allowed at /tmp/zVvv5rwrey line 1:␤------> $_ = "foo"; s[⏏] = 'bar'; 
.say␤Parse failed␤FAILED 00:01 121m␤»
08:54 < TimToady> std: $_ = "foo"; s[f] = 'bar'; .say
08:54 <+p6eval> std 625303c: OUTPUT«ok 00:01 123m␤»
08:54 < TimToady> rakudo should not backtrack there
09:51  * moritz_ submits rakudobug, justin case