From 0b3c8407989901641e41cb5bb66906dd8b7269ce Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 15 Sep 2020 22:02:36 +0900
Subject: [PATCH] [Fix #8720] Fix an error for `Lint/IdentityComparison`

Fixes #8720.

This PR fixes an error for `Lint/IdentityComparison` when
calling `object_id` method without receiver in LHS or RHS.
---
 CHANGELOG.md                                      |  4 ++++
 lib/rubocop/cop/lint/identity_comparison.rb       |  8 +++++---
 spec/rubocop/cop/lint/identity_comparison_spec.rb | 12 ++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index eca06643662..75d6720fae9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#8720](https://github.com/rubocop-hq/rubocop/issues/8720): Fix an error for `Lint/IdentityComparison` when calling `object_id` method without receiver in LHS or RHS. ([@koic][])
+
 ## 0.91.0 (2020-09-15)
 
 ### New features
diff --git a/lib/rubocop/cop/lint/identity_comparison.rb b/lib/rubocop/cop/lint/identity_comparison.rb
index c1b6d6d74ca..eed7956f75f 100644
--- a/lib/rubocop/cop/lint/identity_comparison.rb
+++ b/lib/rubocop/cop/lint/identity_comparison.rb
@@ -26,9 +26,11 @@ def on_send(node)
           return unless compare_between_object_id_by_double_equal?(node)
 
           add_offense(node) do |corrector|
-            receiver = node.receiver.receiver.source
-            argument = node.first_argument.receiver.source
-            replacement = "#{receiver}.equal?(#{argument})"
+            receiver = node.receiver.receiver
+            argument = node.first_argument.receiver
+            return unless receiver && argument
+
+            replacement = "#{receiver.source}.equal?(#{argument.source})"
 
             corrector.replace(node, replacement)
           end
diff --git a/spec/rubocop/cop/lint/identity_comparison_spec.rb b/spec/rubocop/cop/lint/identity_comparison_spec.rb
index 8f3e7b7056b..8699b3fbed8 100644
--- a/spec/rubocop/cop/lint/identity_comparison_spec.rb
+++ b/spec/rubocop/cop/lint/identity_comparison_spec.rb
@@ -31,4 +31,16 @@
       foo.equal(bar)
     RUBY
   end
+
+  it 'does not register an offense when lhs is `object_id` without receiver' do
+    expect_no_offenses(<<~RUBY)
+      object_id == bar.object_id
+    RUBY
+  end
+
+  it 'does not register an offense when rhs is `object_id` without receiver' do
+    expect_no_offenses(<<~RUBY)
+      foo.object_id == object_id
+    RUBY
+  end
 end