From @grondilu

Hello,

I failed converting an object derived from Int using bless​:

code​:

class Foo is Int {}; sub somefoo returns Foo { Foo.bless​: 13 }; say somefoo.WHAT;

  Error​:
  rakudo d61049​: OUTPUT«Type check failed for return value␤ in sub
  somefoo at /tmp/42g2EnvfAS​:1␤ in block <anon> at /tmp/42g2EnvfAS​:1␤␤»

$ perl6 --version
This is perl6 version 2012.04.1-9-g110f35c built on parrot 4.3.0 revision RELEASE_4_3_0-12-gf983396

From @moritz

On Thu May 10 06​:12​:35 2012, grondilu@​yahoo.fr wrote​:

I failed converting an object derived from Int using bless​:

code​:

class Foo is Int {}; sub somefoo returns Foo { Foo.bless​: 13 }; say
somefoo.WHAT;

Error​:
rakudo d61049​: OUTPUT«Type check failed for return value␤  in sub
somefoo at /tmp/42g2EnvfAS&#8203;:1␤ in block \<anon> at

/tmp/42g2EnvfAS​:1␤␤»

Rakudo is actually correct here​: in Perl 6, bless takes an already-built
object, and does initialization stuff (in particular it calls BUILDALL,
which in turns calls the BUILD submethods or does the default attribute
initialization). So Foo.bless​: 13 actually returns the 13, and that
fails your type check.

So, how does one write the constructor for a class that inherits from a
value type?

A rakudo-specific answer is that you can write

class Foo is Int {
  method new($x) {
  nqp​::box_i($x, self)
  }
}

The spec is silent on how to do it in a more general way.
A possible solution is to force all value types to provide a constructor
that you can inherit. So Int.new(4) would return a 4, but

class Foo is Int { }; Foo.new(4)

would return a 4 but of type Foo.

Cheers,
Moritz

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

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