From zefram@fysh.org

$ perl6 -e 'my Nil $a = 3'
Type check failed in assignment to '$a'; expected 'Any' but got 'Int'
  in block <unit> at -e​:1

It is correct to get an error of this general type, but the message
is incorrect in identifying the expected type. The message appears
nonsensical, because an Int would satisfy an Any constraint. A similar
faulty message can be produced in other coercion situations too​:

$ perl6 -e 'sub aa (Nil $a) { }; my $b = 3; aa($b)'
Type check failed in binding $a; expected 'Any' but got 'Int'
  in sub aa at -e​:1
  in block <unit> at -e​:1

I have some suspicion that this faulty message is a result of the
intentional but somewhat surprising behaviour of assigning Nil to
a scalar​:

$ perl6 -e 'my $a = Nil; say $a.perl'
Any

-zefram

From @usev6

The error messages correctly mention Nil now​:

$ perl6 -e 'my Nil $a = 3'
Type check failed in assignment to $a; expected Nil but got Int
  in block <unit> at -e​:1

$ perl6 -e 'sub aa (Nil $a) { }; my $b = 3; aa($b)'
Type check failed in binding $a; expected Nil but got Int
  in sub aa at -e​:1
  in block <unit> at -e​:1

I added two tests to S32-exceptions/misc.t with commit Raku/roast@3fe83cf8dc

I'm closing this ticket as 'resolved'.

@usev6 - Status changed from 'new' to 'resolved'