rdoc -C1 reports alias method arguments as uncovered

# run this with rdoc -C  rdoc_bug.rb and it looks fully covered.
# run this with rdoc -C1 rdoc_bug.rb to see that aliases arguments aren't covered.

##
# Instance methods

module InstanceMethods
  ##
  # Takes a +value+ or a +block+ and returns a value monad.

  def _ value = nil, &block
    # ...
  end

  alias value  _
  alias expect _
end

reports:

The following items are not documented:

  module InstanceMethods # is documented

    # in file rdoc_bug.rb
    # +value+, +block+ is not documented
    def expect(value = nil, &block); end

    # in file rdoc_bug.rb
    # +value+, +block+ is not documented
    def value(value = nil, &block); end

  end

Start by reproducing the report with rdoc -C and rdoc -C1 on the shown rdoc_bug.rb example, then trace how RDoc handles the aliased methods value and expect. Done means the -C1 report no longer incorrectly marks the aliases' value and block arguments as undocumented.