Add args forwarding specs

[palkan]

Related to #745.

This is a basic args forwarding spec (extracted from ruby-next).

I tried to add a spec for brackets-less case like this:

it "treats arguments as Range when brackets are ommitted" do
  a = Class.new(F)
  a.class_eval(<<-RUBY)
      def delegate(...)
        target ...
      end
   RUBY

   # this passes
   a.new.delegate(1, b: 2).should == [[], {}]
end

But I'm not sure why the result is empty (testing in 2.7.0)? Shouldn't there be a beginless-endless range?

[eregon]

Could you nest this under DelegationSpecs and name it more explicitly like Target?
That will also fix the CI.

[eregon]

The filename has a typo (missing d).
I think this should be called delegation_spec.rb and later on we could extend specs in this file with how delegation is achieved in various versions.

[eregon]

Re the parentheses-less version, I see this (on 2.7.0):

class F
  def target(*args, **kwargs)
    [args, kwargs]
  end
end

a = Class.new(F)
a.class_eval(<<-RUBY)
def delegate(...)
  target ...
end
RUBY

p a.new.delegate(1, b: 2)
# => [[], {}]...

So it's the same as target()....
That would be good to spec, yes.

[palkan]

Thanks for the review! Pushed the updated version.

[eregon]

Looks great!