Unable to show errors that occur within nesting.

[kojix2]

class Cat
  def mew
    "meow"
  end

  def count   #  ^ ^
    1 + # error (*ω*) oO ( one, one .. and .. and?
  end
end

IRuby shows an error as an execution result.

When you use Jupyter Notebook, you don't think in the Object Oriented Way.
You rarely create your own classes or modules.
I think that's why Nobody point out this obvious bug for a long time.