From @masak

<masak> r​: sub foo(X of X) { }
<p6eval> rakudo e765c9​: OUTPUT«===SORRY!===␤Method 'parameterize' not
found for invocant of class 'Perl6​::Metamodel​::PackageHOW'␤»
* masak submits rakudobug
<masak> std​: sub foo(X of X) { }
<p6eval> std 64edd1c​: OUTPUT«===SORRY!===␤In parameter declaration,
typename 'X' must be predeclared (or marked as declarative with :​:
prefix) [...] FAILED 00​:00 42m␤»

I prefer STD.pm6's error message here. Rakudo's error message feels
like an internal leakage of some kind.

Courtesy of diakopter++.

From @jnthn

On Sun Oct 21 02​:45​:27 2012, masak wrote​:

<masak> r​: sub foo(X of X) { }
<p6eval> rakudo e765c9​: OUTPUT«===SORRY!===␤Method 'parameterize' not
found for invocant of class 'Perl6​::Metamodel​::PackageHOW'␤»
* masak submits rakudobug
<masak> std​: sub foo(X of X) { }
<p6eval> std 64edd1c​: OUTPUT«===SORRY!===␤In parameter declaration,
typename 'X' must be predeclared (or marked as declarative with :​:
prefix) [...] FAILED 00​:00 42m␤»

STD doesn't know about the X exception package, however. Anyway, now there's a good error​:

$ perl6-m -e "sub foo(X of X) { }"
===SORRY!=== Error while compiling -e
X cannot be parameterized
at -e​:1
------> sub foo(X of X<HERE>) { }

Tests in S32-misc/exceptions.t.

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

@jnthn - Status changed from 'open' to 'resolved'