From @MARTIMM

In the piece of code shown below perl6 generates a wrong message. In the
original code there were more multi methods but could bring it down to one.

#!/usr/bin/env perl6
#
use v6;
use BSON​::Javascript;

class C {
  multi method c1 ( BSON​::Javascript $js1,
  BSON​::Javascript :$js2 = ''
  ) {
  }
}

my C $ic .= new();
my BSON​::Javascript $bjs .= new(javascript => 'function(){}');
$ic.c1($bjs);

The error generated is;

Cannot call 'c1'; none of these signatures match​:
:(C $​: BSON​::Javascript $js1, BSON​::Javascript :js2($js2) = { ... }, *%_)
  in block <unit> at i.pl6​:17

This message leads you to investigating the call to the method which is
wrong. When the 'multi' is removed from the method, the real problem
gets revealed;

Type check failed in binding $js2; expected 'BSON​::Javascript' but got 'Str'
  in method c1 at i.pl6​:7
  in block <unit> at i.pl6​:17

The used Perl version is;
This is perl6 version 2015.01-77-gd320f00 built on MoarVM version
2015.01-21-g4ee4925

Greetings,
Marcel Timmerman
@​MARTIMM on github

From @jnthn

On Sat Feb 21 07​:33​:27 2015, mt1957@​gmail.com wrote​:

In the piece of code shown below perl6 generates a wrong message. In the
original code there were more multi methods but could bring it down to one.

#!/usr/bin/env perl6
#
use v6;
use BSON​::Javascript;

class C {
multi method c1 ( BSON​::Javascript $js1,
BSON​::Javascript :$js2 = ''
) {
}
}

my C $ic .= new();
my BSON​::Javascript $bjs .= new(javascript => 'function(){}');
$ic.c1($bjs);

The error generated is;

Cannot call 'c1'; none of these signatures match​:
:(C $​: BSON​::Javascript $js1, BSON​::Javascript :js2($js2) = { ... }, *%_)
in block <unit> at i.pl6​:17

This message leads you to investigating the call to the method which is
wrong. When the 'multi' is removed from the method, the real problem
gets revealed;

Type check failed in binding $js2; expected 'BSON​::Javascript' but got 'Str'
in method c1 at i.pl6​:7
in block <unit> at i.pl6​:17

The used Perl version is;
This is perl6 version 2015.01-77-gd320f00 built on MoarVM version
2015.01-21-g4ee4925

We now actually go so far as to catch this one at compile time. So, a golfed version of the script submitted​:

class BSON​::Javascript { }
class C {
  multi method c1 ( BSON​::Javascript $js1,
  BSON​::Javascript :$js2 = ''
  ) {
  }
}

Now fails to compile with​:

===SORRY!=== Error while compiling bug3.p6
Default value '' will never bind to a parameter of type BSON​::Javascript
at bug3.p6​:2
------> multi c1 (BSON​::Javascript :$js2 = ''<HERE>) { }

Added a regression test in S06-signature/optional.t.

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

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