[perl #74664] [BUG] LTA error message for attempting to use a signature in a list assignment

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# New Ticket Created by  Stefan O'Rear 
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15:14 < sorear> rakudo: my ($foo, $bar = "baz") = <a>; say "$foo $bar"
15:14 <+p6eval> rakudo e393c7: OUTPUT«Undefined value shifted from empty 
                array␤current instr.: 'perl6;Perl6Exception;throw' pc 14877 
                (src/builtins/Seq.pir:28)␤»
15:20 <@jnthn> I think we probably should just complain at parse time actually.
15:20 <@jnthn> We parse a signature there, but if you're starting to stick in 
               optional parameters and stuff, we just say "oh noes, that's too 
               complex to turn into a list".
15:20 <@jnthn> If you want full signature semantics, use binding, not 
               assignment.
15:21 <@jnthn> Us not complaining about the signature being too complex is a 
               rakudo fail.
15:21 <@jnthn> It's a bit annoying implementation wise.
15:21 <@jnthn> Because you parse a signature always but in the = case you want 
               to do list assignment.
15:22 <@jnthn> So you need to turn the signature into a list.
15:22 <@jnthn> Which doesn't make sense if it's anything complex.