[perl #106932] Junctions in subsignatures can cause infinite recursion

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# New Ticket Created by  Stefan O'Rear 
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21:09 < sorear> rakudo: sub foo(Mu $x [ $y ]) { }; foo([ any(1,2,3) ])
21:09 <+p6eval> rakudo eb6c4b: OUTPUT«(timeout)maximum recursion depth 
                exceeded␤»

There's no direct junction, so AUTOTHREAD makes no progress when called.