class Common
  def func(x)
    yield 1
  end
end

class Foo
  def foo
    Common.new.func("str") do |x|
      1
    end
  end
end

class Bar
  def bar
    Common.new.func(:sym) do |x|
      :sym2
    end
  end
end

Foo.new.foo
Bar.new.bar

__END__
# Classes
class Common
  def func: (:sym | String) { (Integer) -> (:sym2 | Integer) } -> (:sym2 | Integer)
end

class Foo
  def foo: -> (:sym2 | Integer)
end

class Bar
  def bar: -> (:sym2 | Integer)
end
