[perl #131251] Useless use warning triggered on assignment forms of reverse metaops

[Zoffix Znet via RT]

On Wed, 03 May 2017 19:14:23 -0700, b...@abrij.org wrote:
> 
> An R metaop using the bracket notation to retain lvalueness of the
> lvalue side
> triggers a "useless use" warning in sink context, and shouldn't.
> 
> (10:00:22 PM) skids: m: my $a = "H"; say $a [R~]= "T"; $a.say; $a
> [R~]= "W"; $a.say
> (10:00:22 PM) camelia: rakudo-moar f4cbdb: OUTPUT: «Potential
> difficulties:␤    Useless use of [R~]= in sink context␤    at <tmp>:1␤
> ------>  $a = "H"; say $a [R~]= "T"; $a.say; $a ⏏[R~]= "W";
> $a.say␤TH␤TH␤WTH␤»


Using fix:  Fix spurious useless-use warnings in metaop+metaassign op
Using test: Fix spurious useless-use warnings in metaop+metaassign op

Thank you for the report. This is now fixed.

Fix:  https://github.com/rakudo/rakudo/commit/cad66b72d57637f
Test: https://github.com/rakudo/rakudo/commit/cad66b72d57637f

(P.S.: couldn't figure out a combination with `S` meta op that did not explode 
about missing CALL-ME methods, so I didn't cover that one in tests)