From 839e35b80169efcd70b7528c335931a3396468a0 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Thu, 9 Jul 2020 19:20:48 +0900
Subject: [PATCH] [Fix #147] Fix an error for `Performance/AncestorsInclude`

Fixes #147.

This PR fixes an error for `Performance/AncestorsInclude`
when using `ancestors.include?` without receiver.
---
 CHANGELOG.md                                          |  4 ++++
 lib/rubocop/cop/performance/ancestors_include.rb      |  4 +++-
 .../rubocop/cop/performance/ancestors_include_spec.rb | 11 +++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index df8e78e0a7..baff248f7e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#147](https://github.com/rubocop-hq/rubocop-performance/issues/147): Fix an error for `Performance/AncestorsInclude` when using `ancestors.include?` without receiver. ([@koic][])
+
 ### Changes
 
 * [#149](https://github.com/rubocop-hq/rubocop-performance/pull/149): Mark `Performance/AncestorsInclude` as unsafe. ([@eugeneius][])
diff --git a/lib/rubocop/cop/performance/ancestors_include.rb b/lib/rubocop/cop/performance/ancestors_include.rb
index ab02fac7c7..f50b57d4b6 100644
--- a/lib/rubocop/cop/performance/ancestors_include.rb
+++ b/lib/rubocop/cop/performance/ancestors_include.rb
@@ -35,7 +35,9 @@ def on_send(node)
         def autocorrect(node)
           ancestors_include_candidate?(node) do |subclass, superclass|
             lambda do |corrector|
-              corrector.replace(node, "#{subclass.source} <= #{superclass.source}")
+              subclass_source = subclass ? subclass.source : 'self'
+
+              corrector.replace(node, "#{subclass_source} <= #{superclass.source}")
             end
           end
         end
diff --git a/spec/rubocop/cop/performance/ancestors_include_spec.rb b/spec/rubocop/cop/performance/ancestors_include_spec.rb
index d870eff2d7..cd81456018 100644
--- a/spec/rubocop/cop/performance/ancestors_include_spec.rb
+++ b/spec/rubocop/cop/performance/ancestors_include_spec.rb
@@ -14,6 +14,17 @@
     RUBY
   end
 
+  it 'registers an offense and corrects when using `ancestors.include?` without receiver' do
+    expect_offense(<<~RUBY)
+      ancestors.include?(Klass)
+      ^^^^^^^^^^^^^^^^^^ Use `<=` instead of `ancestors.include?`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      self <= Klass
+    RUBY
+  end
+
   it 'does not register an offense when using `<=`' do
     expect_no_offenses(<<~RUBY)
       Class <= Kernel