Feels to me that Nil should not be allowed as a type constraint at all.
> On 27 Feb 2017, at 09:11, Zefram (via RT) <perl6-bugs-follo...@perl.org> > wrote: > > # New Ticket Created by Zefram > # Please include the string: [perl #130875] > # in the subject line of all future correspondence about this issue. > # <URL: https://rt.perl.org/Ticket/Display.html?id=130875 > > > >> my Int $a of Nil > ===SORRY!=== Error while compiling: > Mu not allowed here; variable list already declared with type Int > at line 2 > ------> <BOL>^<EOL> > expecting any of: > constraint >> my Nil $a of Int > ===SORRY!=== Error while compiling: > Int not allowed here; variable list already declared with type Mu > at line 2 > ------> <BOL>^<EOL> > expecting any of: > constraint > > In both of these cases of multiple type constraints, the Nil type > constraint is incorrectly described as "Mu". The same problem > also occurs if both type constraints are specified in the "of" form. > The error messages are otherwise correct, and the corresponding messages > for other types are correct. A Nil type constraint specified without > a clash actually behaves (mostly correctly) as a Nil type constraint, > not as a Mu type constraint. > > -zefram
