Module function without argument

[thyresias]

This supports module_function without argument (#1823).
I had initially the intention to use a special value for @visibibility, but I think it is better that it has actual visibility values, so I introduced @module_function_mode.

[st0012]

This condition doesn't check @scanner.in_proc_block and it means in cases like

module M
  Module.new do
    module_function
  end

  def outer; end
end

The private visibility leaks outside of the anonymous module.

[st0012]

Let's also add this test:

def test_module_function_no_arg_does_not_leak_from_block
  util_parser <<~RUBY
    module M
      Module.new do
        module_function
      end
      def outer; end
    end
  RUBY

  mod = @store.find_module_named 'M'
  methods = mod.method_list.map { |method| [method.name, method.singleton, method.visibility] }
  assert_equal [['outer', false, :public]], methods
end

[tompng]

Visibility and module_function_mode are exclusive.
We don't want to introduce instance values with complex dependencies. Simple internal representation is better.
How about changing attr_accessor :visibility to attr_accessor :visibility_mode
and define def visibility that computes actual visibility from exclusive state like this?

attr_accessor :visibility_mode   # :public, :private, :protected, :module_function

def visibility
  @visibility_mode == :module_function ? :private : @visibility_mode
end

[tompng]

singleton is always nil because the local variable is not assigned yet.
I think it's a mistake of @scanner.singleton, but module_function_mode is only set on non-singleton module scope. Simply removing && (singleton_check_expression) is enough.

[tompng]

I think it's better to check singleton in _visit_call_module_function.

module A
  class << A
    module_function rescue p($!) # NameError, RDoc should just ignore it
    def f; end # public method
  end
end