From @jonathanstowe

It appears that the Metamodel​::WrapDispatcher can't find the candidate to execute when the wrapped method is pre-compiled.

This can be recreated in several ways, first by wrapping the method in an over-ridden add_method​:

lib/Vum.pm​:

class MetamodelX​::FooHOW is Metamodel​::ClassHOW {
  method add_method(Mu \type, $name, &code) {
  say "adding $name";
  my &wrapper = method (|c) { say "running $name"; callsame; };
  &code.wrap( &wrapper );
  self.Metamodel​::ClassHOW​::add_method(type, $name, &code);
  }
  method compose(Mu \type) {
  self.Metamodel​::ClassHOW​::compose(type);
  }
}

my package EXPORTHOW {
  package SUPERSEDE {
  constant class = MetamodelX​::FooHOW;
  }
}

And lib/Boo.pm :

use Vum;

#no precompilation;

class Boo {
  has $.rabble;
  method rack() {
  say "rabble : ";
  }
}

And exercised with "perl6 -Ilib ..."​:

use Boo;

my $b = Boo.new(rabble => "hoodoo");

say $b.rack;

This will fail with​:

Cannot invoke this object
  in method <anon> at /home/jonathan/devel/perl6/Vum/lib/Vum.pm (Vum) line 4
  in any enter at gen/moar/m-Metamodel.nqp line 3947
  in block <unit> at tt line 5

(Which points to the enter method of WrapDispatch.) Which would appear that it is not getting the appropriate Callable from .candidates[0]. With the "no precompilation" un-commented in Boo.pm this will work fine.

Just to check that this wasn't something mysterious in the MOP it can also be replicated with​:

lib/Wom.pm​:

module Wom {
  multi sub trait_mod​:<is>(Method $m, :$brapped!) is export {
  $m.wrap(method (|c) { say "wrapped"; callsame });
  }
}

lib/Bok.pm​:

use Wom;

#no precompilation;

class Bok {
  has $.rabble;
  method rack() is brapped {
  say "rabble : ";
  }
}

And exercised with the similar script run with "perl6 -Ilib ..." :

use Bok;

my $b = Bok.new(rabble => "hoodoo");

say $b.rack;

Then this will also fail identically without the "no precompilation".

This afflicts OO​::Monitors in the ecosystem which cannot be used in a module that will be precompiled, and I suspect this is also at the heart of a problem with Staticish which similarly doesn't work if used in a module which is precompiled.

This is with​:

This is Rakudo version 2016.03-98-g61d231c built on MoarVM version 2016.03-84-g4afd7b6

From @LLFourn

For reference this is another related to​:

https://rt.perl.org/Public/Bug/Display.html?id=125634

On Sat, Apr 9, 2016 at 7​:10 AM Jonathan Stowe <perl6-bugs-followup@​perl.org>
wrote​:

# New Ticket Created by Jonathan Stowe
# Please include the string​: [perl #​127860]
# in the subject line of all future correspondence about this issue.
# <URL​: https://rt-archive.perl.org/perl6/Ticket/Display.html?id=127860 >

It appears that the Metamodel​::WrapDispatcher can't find the candidate to
execute when the wrapped method is pre-compiled.

This can be recreated in several ways, first by wrapping the method in an
over-ridden add_method​:

lib/Vum.pm​:

class MetamodelX​::FooHOW is Metamodel​::ClassHOW {
method add_method(Mu \type, $name, &code) {
say "adding $name";
my &wrapper = method (|c) { say "running $name"; callsame; };
&code.wrap( &wrapper );
self.Metamodel​::ClassHOW​::add_method(type, $name, &code);
}
method compose(Mu \type) {
self.Metamodel​::ClassHOW​::compose(type);
}
}

my package EXPORTHOW {
package SUPERSEDE {
constant class = MetamodelX​::FooHOW;
}
}

And lib/Boo.pm :

use Vum;

#no precompilation;

class Boo {
has $.rabble;
method rack() {
say "rabble : ";
}
}

And exercised with "perl6 -Ilib ..."​:

use Boo;

my $b = Boo.new(rabble => "hoodoo");

say $b.rack;

This will fail with​:

Cannot invoke this object
in method <anon> at /home/jonathan/devel/perl6/Vum/lib/Vum.pm (Vum) line
4
in any enter at gen/moar/m-Metamodel.nqp line 3947
in block <unit> at tt line 5

(Which points to the enter method of WrapDispatch.) Which would appear
that it is not getting the appropriate Callable from .candidates[0]. With
the "no precompilation" un-commented in Boo.pm this will work fine.

Just to check that this wasn't something mysterious in the MOP it can also
be replicated with​:

lib/Wom.pm​:

module Wom {
multi sub trait_mod​:<is>(Method $m, :$brapped!) is export {
$m.wrap(method (|c) { say "wrapped"; callsame });
}
}

lib/Bok.pm​:

use Wom;

#no precompilation;

class Bok {
has $.rabble;
method rack() is brapped {
say "rabble : ";
}
}

And exercised with the similar script run with "perl6 -Ilib ..." :

use Bok;

my $b = Bok.new(rabble => "hoodoo");

say $b.rack;

Then this will also fail identically without the "no precompilation".

This afflicts OO​::Monitors in the ecosystem which cannot be used in a
module that will be precompiled, and I suspect this is also at the heart of
a problem with Staticish which similarly doesn't work if used in a module
which is precompiled.

This is with​:

This is Rakudo version 2016.03-98-g61d231c built on MoarVM version
2016.03-84-g4afd7b6

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

From jns@gellyfish.co.uk

I'm actually surprised there are as few "Cannot invoke this object"
tickets​:

https://rt.perl.org/Search/Simple.html?q=%22Cannot+invoke+this+object%2
2

A cursory survey of those would suggest that they all fall in a wider
category of "code attribute of some type not surviving precompilation"

On Sat, 2016-04-09 at 03​:24 -0700, Lloyd Fournier via RT wrote​:

For reference this is another related to​:

https://rt.perl.org/Public/Bug/Display.html?id=125634

On Sat, Apr 9, 2016 at 7​:10 AM Jonathan Stowe <perl6-bugs-followup@​pe
rl.org>
wrote​:

# New Ticket Created by  Jonathan Stowe
# Please include the string​:  [perl #​127860]
# in the subject line of all future correspondence about this
issue.
# <URL​: https://rt-archive.perl.org/perl6/Ticket/Display.html?id=127860 >

It appears that the Metamodel​::WrapDispatcher can't find the
candidate to
execute when the wrapped method is pre-compiled.

This can be recreated in several ways, first by wrapping the method
in an
over-ridden add_method​:

lib/Vum.pm​:

class MetamodelX​::FooHOW is Metamodel​::ClassHOW {
    method add_method(Mu \type, $name, &code) {
        say "adding $name";
        my &wrapper = method (|c) { say "running $name"; callsame;
};
        &code.wrap( &wrapper );
        self.Metamodel​::ClassHOW​::add_method(type, $name, &code);
   }
   method compose(Mu \type) {
       self.Metamodel​::ClassHOW​::compose(type);
   }
}

my package EXPORTHOW {
    package SUPERSEDE {
       constant class = MetamodelX​::FooHOW;
    }
}

And lib/Boo.pm :

use Vum;

#no precompilation;

class Boo {
   has $.rabble;
   method rack() {
      say "rabble : ";
   }
}

And exercised with "perl6 -Ilib ..."​:

use Boo;

my $b = Boo.new(rabble => "hoodoo");

say $b.rack;

This will fail with​:

Cannot invoke this object
  in method <anon> at /home/jonathan/devel/perl6/Vum/lib/Vum.pm
(Vum) line
4
  in any enter at gen/moar/m-Metamodel.nqp line 3947
  in block <unit> at tt line 5

(Which points to the enter method of WrapDispatch.) Which would
appear
that it is not getting the appropriate Callable from
.candidates[0]. With
the "no precompilation" un-commented in Boo.pm this will work fine.

Just to check that this wasn't something mysterious in the MOP it
can also
be replicated with​:

lib/Wom.pm​:

module Wom {
   multi sub trait_mod​:<is>(Method $m, :$brapped!) is export {
      $m.wrap(method (|c) { say "wrapped"; callsame });
   }
}

lib/Bok.pm​:

use Wom;

#no precompilation;

class Bok {
   has $.rabble;
   method rack() is brapped {
      say "rabble : ";
   }
}

And exercised with the similar script run with "perl6 -Ilib ..." :

use Bok;

my $b = Bok.new(rabble => "hoodoo");

say $b.rack;

Then this will also fail identically without the "no
precompilation".

This afflicts OO​::Monitors in the ecosystem which cannot be used in
a
module that will be precompiled, and I suspect this is also at the
heart of
a problem with Staticish which similarly doesn't work if used in a
module
which is precompiled.

This is with​:

This is Rakudo version 2016.03-98-g61d231c built on MoarVM version
2016.03-84-g4afd7b6