False positive with Style/MissingRespondToMissing when using inline access modifiers

[voikya]

When using inline access modifiers (like private def respond_to_missing?(...)), the Style/MissingRespondToMissing is inappropriately returning a false positive, stating there is no respond_to_missing? method defined.

Both of these methods are initially defined as private:

BasicObject.private_method_defined?(:method_missing)
 => true

Kernel.private_method_defined?(:respond_to_missing?)
 => true

---

Expected behavior

The Style/MissingRespondToMissing should not report an issue if respond_to_missing? is defined using an inline private modifier.

Actual behavior

Rubocop validation fails.

Steps to reproduce the problem

Rubocop configuration:

Style/AccessModifierDeclarations:
  EnforcedStyle: inline

Style/MissingRespondToMissing:
  Enabled: true

Test file:

class Test
  private def method_missing(method, *args, &block)
    super
  end

  private def respond_to_missing?(method, include_private = false)
    super
  end
end

Result:

test.rb:2:11: C: Style/MissingRespondToMissing: When using method_missing, define respond_to_missing?.
  private def method_missing(method_id, *args, &block) ...

In contrast, no issue is reported with this file, using group-style access modifiers:

class Test
  private
  def method_missing(method_id, *args, &block)
    super
  end

  def respond_to_missing?(method, include_private = false)
    super
  end
end

RuboCop version

$ rubocop -V
0.88.0 (using Parser 2.7.1.4, rubocop-ast 0.1.0, running on ruby 2.6.6 x86_64-darwin19)