[perl #127025] Multimethods from a role fail to probe all where clauses during dispatch

[Brian S. Julin]

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Regression:

(09:51:30 PM) camelia: rakudo-moar e360bd: OUTPUT«1␤»
(09:51:57 PM) skids: m: role A { multi method a ($ where { $_.say; $_ ~~ /a/ } 
) { "A".say }; multi method a ($ where { $_.say; $_ ~~ /b/ } ) { "B".say } }; 
class C does A { }; C.new.a("a");
(09:51:57 PM) camelia: rakudo-moar e360bd: OUTPUT«a␤a␤A␤»
(09:52:02 PM) skids: m: role A { multi method a ($ where { $_.say; $_ ~~ /a/ } 
) { "A".say }; multi method a ($ where { $_.say; $_ ~~ /b/ } ) { "B".say } }; 
class C does A { }; C.new.a("b");
(09:52:02 PM) camelia: rakudo-moar e360bd: OUTPUT«b␤Cannot call a(C.new: "b"); 
none of these signatures match:␤    (C $: $ where { ... }, *%_)␤  in block 
<unit> at /tmp/10zZDctR_z line 1␤␤»
(09:52:08 PM) skids: star: role A { multi method a ($ where { $_.say; $_ ~~ /a/ 
} ) { "A".say }; multi method a ($ where { $_.say; $_ ~~ /b/ } ) { "B".say } }; 
class C does A { }; C.new.a("b");
(09:52:09 PM) camelia: star-m 2015.09: OUTPUT«b␤b␤b␤B␤»

Classes seem to be OK:

(09:55:47 PM) skids: m: class C { multi method a ($ where { $_.say; $_ ~~ /a/ } 
) { "A".say }; multi method a ($ where { $_.say; $_ ~~ /b/ } ) { "B".say } }; 
C.new.a("a"); C.new.a("b");
(09:55:47 PM) camelia: rakudo-moar e360bd: OUTPUT«a␤a␤A␤b␤b␤b␤B␤»