.rubocop.yml

AllCops:
  DisabledByDefault: true

Style/TopLevelMethodDefinition:
  Enabled: true

broken.rb

class One
  def two
    2
  end
end

def one
  1
end

Gemfile

# frozen_string_literal: true

source "https://rubygems.org"

git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }

gem "rubocop"

output.txt

❯ rubocop --debug
For /Users/dev/projects/rubocop-bug: configuration from /Users/dev/projects/rubocop-bug/.rubocop.yml
Default configuration from /Users/dev/.rbenv/versions/2.7.3/lib/ruby/gems/2.7.0/gems/rubocop-1.15.0/config/default.yml
Inspecting 3 files
Scanning /Users/dev/projects/rubocop-bug/Gemfile
Loading cache from /Users/dev/.cache/rubocop_cache/c00b397a11a60e0fa0171c84ff7b86bed54ca9f3/6d7a3b621ca1730e04accd938619e4bdab66cfb1/9a72538d2e9b9b74fa91e1ebf6f6587f9cdb5cac
.Scanning /Users/dev/projects/rubocop-bug/broken.rb
Loading cache from /Users/dev/.cache/rubocop_cache/c00b397a11a60e0fa0171c84ff7b86bed54ca9f3/6d7a3b621ca1730e04accd938619e4bdab66cfb1/f6397e6482b48540814a82460e9e0c74f45a636e
.Scanning /Users/dev/projects/rubocop-bug/works.rb
Loading cache from /Users/dev/.cache/rubocop_cache/c00b397a11a60e0fa0171c84ff7b86bed54ca9f3/6d7a3b621ca1730e04accd938619e4bdab66cfb1/ea14c4e0525a37b192467d7a2cb78d8e2efdc75b
C

Offenses:

works.rb:1:1: C: Style/TopLevelMethodDefinition: Do not define methods at the top-level.
def one ...
^^^^^^^

3 files inspected, 1 offense detected
Finished in 0.3944059999776073 seconds

works.rb

def one
  1
end