From @moritz

08​:53 <@​moritz_> rakudo​: class A { }; class B does A { }; say "alive"
08​:53 < p6eval> rakudo 99ad1e​: OUTPUT«Method '!select' not found for
invocant of class ''␤»

I think abusing a class as a role is forbidden, but the error message
could be more awesome.

Cheers,
Moritz

From @chromatic

On Monday 06 July 2009 23​:55​:28 Moritz Lenz wrote​:

I think abusing a class as a role is forbidden

I hope it's not!

-- c

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

From @moritz

chromatic wrote​:

On Monday 06 July 2009 23​:55​:28 Moritz Lenz wrote​:

I think abusing a class as a role is forbidden

I hope it's not!

Well, it surely depends on context. You can "pun" a role into a class by
instantiating it, but the correct way to apply it to another class seems
to be with 'does', not 'is'.

I haven't found a concrete reference in the specs if it's actually
forbidden, a comment from jnthn or TimToady would be appreciated.

Cheers,
Moritz

From @jnthn

Moritz Lenz wrote​:

chromatic wrote​:

On Monday 06 July 2009 23​:55​:28 Moritz Lenz wrote​:

I think abusing a class as a role is forbidden

I hope it's not!

Well, it surely depends on context. You can "pun" a role into a class by
instantiating it, but the correct way to apply it to another class seems
to be with 'does', not 'is'.

As it stands right now...

class C does R { } # composes the role
class C is R { } # inherits from the pun
class C1 is C2 { } # plain old class inheritance
class C1 does C2 { } # fails

I haven't found a concrete reference in the specs if it's actually
forbidden, a comment from jnthn or TimToady would be appreciated.

I've heard the whole "every class implies a role" and "you can take a
role as an immutable snapshot of a class" stuff touted now and then, but
as moritz points out, there's nothing concrete in the spec about that.
Unless that changes (which I'm open to it doing), don't expect Rakudo's
current semantics to change on this (aside from awesomizing the error
message).

Thanks,

Jonathan

From @jnthn

On Mon Jul 06 23​:55​:28 2009, moritz wrote​:

08​:53 <@​moritz_> rakudo​: class A { }; class B does A { }; say "alive"
08​:53 < p6eval> rakudo 99ad1e​: OUTPUT«Method '!select' not found for
invocant of class ''␤»

While at some point we may end up spec'ing that you actually get your
class snapshotted to make a role, that's not the case yet. So I
awesomized the error​:

class A { }; class B does A { }
Can only use does with a role, but A is not one

Giving to moritz++ for spectests (I guess one to check that we get an
error mentioning A will do fine).

Thanks,

Jonathan

From @kyleha

This is an automatically generated mail to inform you that tests are now available in t/spec/S14-roles/basic.t

commit 4b8222394636ac4bb66f3661dfa9cee5dc0f30b2
Author​: moritz <moritz@​c213334d-75ef-0310-aa23-eaa082d1ae64>
Date​: Mon May 24 14​:46​:29 2010 +0000

  [t/spec] tests for RT #​67278, non-awesome error message for class Foo does NonRole
 
  git-svn-id​: http://svn.pugscode.org/pugs@&#8203;30777 c213334d-75ef-0310-aa23-eaa082d1ae64

diff --git a/t/spec/S14-roles/basic.t b/t/spec/S14-roles/basic.t
index 405e2ba..9d48c95 100644
--- a/t/spec/S14-roles/basic.t
+++ b/t/spec/S14-roles/basic.t
@@ -114,6 +114,15 @@ eval_dies_ok '0 but RT66178', '"but" with non-existent role dies';
        '... and the error message mentions the role';
 }
 
+# RT #67278
+{
+    class AClass { };
+    my $x = eval 'class BClass does AClass { }; 1';
+    nok $x, 'class SomeClass does AnotherClass  dies';
+    ok "$!" ~~ /AClass/, 'Error message mentions the offending non-role';
+
+}
+
 done_testing;
 
 # vim: ft=perl6

From @moritz

... and now tested appropriately.

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