Parse failure with signature unpacking on anon Callable param

[zoffixznet]

3rd code should work just the same as 2nd code does

m: -> & {}(-> {})
rakudo-moar 202459ce0: OUTPUT: «»

m: -> &z:() {}(-> {})
rakudo-moar 202459ce0: OUTPUT: «»

m: -> &:() {}(-> {})
rakudo-moar 202459ce0: OUTPUT: «(exit code 1) Cannot unpack or Capture `->  { #`(Block|94478251310560) ... }`.␤To create a…»

<Zoffix> I think that ticket can be fixed by just changing this line
    to `<subshortname> | <sigterm> | <subshortname> <sigterm>` 
    https://github.com/rakudo/rakudo/blob/202459ce0b9cf0170339d543529c9415d52ac3d4/src/Perl6/Grammar.nqp#L582