From zefram@fysh.org

$ ./perl6 -e 'sub aa (Mu​:U :​:T) { say T; my T $a = T; say $a.WHAT; }; aa(Int); aa(Nil)'
(Int)
(Int)
Nil
Method 'gist' not found for invocant of class 'T'
  in sub aa at -e​:1
  in block <unit> at -e​:1

I'm mystified as to how the gist method goes missing there. It seems
entirely available when I'm not using a type parameter​:

$ ./perl6 -e 'say Int; my Int $a = Int; say $a.WHAT; say Nil; my Nil $b = Nil; say $b.WHAT;'
(Int)
(Int)
Nil
Nil

I also don't get an error if the "= T" is omitted, which is bizarre
because the variable contains the same value by default. The error
doesn't occur at the time of the assignment, though​: it only happens
with the say statement.

-zefram

From @AlexDaniel

That's a nice one. Still reproducible (2017.11, HEAD(5929887))

On 2015-09-20 09​:29​:41, zefram@​fysh.org wrote​:

$ ./perl6 -e 'sub aa (Mu​:U :​:T) { say T; my T $a = T; say $a.WHAT; };
aa(Int); aa(Nil)'
(Int)
(Int)
Nil
Method 'gist' not found for invocant of class 'T'
in sub aa at -e​:1
in block <unit> at -e​:1

I'm mystified as to how the gist method goes missing there. It seems
entirely available when I'm not using a type parameter​:

$ ./perl6 -e 'say Int; my Int $a = Int; say $a.WHAT; say Nil; my Nil
$b = Nil; say $b.WHAT;'
(Int)
(Int)
Nil
Nil

I also don't get an error if the "= T" is omitted, which is bizarre
because the variable contains the same value by default. The error
doesn't occur at the time of the assignment, though​: it only happens
with the say statement.

-zefram

The RT System itself - Status changed from 'new' to 'open'