How to add an attribute and its accessors in Raku using add_attribute()?

Question

I have this program:

class Foo {
  has $.first;
}

my $a = Attribute.new(
          :name('$!second'),
          :type(Int),
          :package('Foo'),
          :has_accessor(True)
        );
Foo.^add_attribute($a);
Foo.^compose;

Foo.^attributes».say; # Mu $!first␤Int $!second␤

my $foo = Foo.new: :42first, :21second;

$foo.second.say; # P6opaque: no such attribute '$!second' on type Foo in a Foo when trying to get a value

The attributes method shows that the attribute has been added, creating an object apparently succeeds, yet when I try to access the $!second attribute I receive an error.

What am I missing?

Answer 1

What am I missing?

Looks like you're not missing anything. Looks like a bug to me.

At this stage of RakuAST development, I don't think it will get fixed.

If you're really into building classes programmatically, I'd suggest you start looking into using RakuAST.

Documentation is still mostly absent, but there's a powerful .AST method that you can run on sample code, that will produce the RakuAST statements needed to create that code. For example:

$ raku -e 'say Q|class A { has $.a; has $.b }|.AST'
RakuAST::StatementList.new(
  RakuAST::Statement::Expression.new(
    expression => RakuAST::Package.new(
      declarator => "class",
      name       => RakuAST::Name.from-identifier("A"),
      body       => RakuAST::Block.new(
        body => RakuAST::Blockoid.new(
          RakuAST::StatementList.new(
            RakuAST::Statement::Expression.new(
              expression => RakuAST::VarDeclaration::Simple.new(
                scope       => "has",
                sigil       => "\$",
                twigil      => ".",
                desigilname => RakuAST::Name.from-identifier("a")
              )
            ),
            RakuAST::Statement::Expression.new(
              expression => RakuAST::VarDeclaration::Simple.new(
                scope       => "has",
                sigil       => "\$",
                twigil      => ".",
                desigilname => RakuAST::Name.from-identifier("b")
              )
            )
          )
        )
      )
    )
  )
)