[Fix rubocop#217] Fix a false positive for Performance/RedundantEqualityComparisonBlock

Fixes rubocop#217.

This PR fixes a false positive for `Performance/RedundantEqualityComparisonBlock`
when using block argument is used for an argument of `is_a`.

Author: koic

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#214](https://github.com/rubocop/rubocop-performance/issues/214): Fix a false positive for `Performance/RedundantEqualityComparisonBlock` when using multiple block arguments. ([@koic][])
+* [#217](https://github.com/rubocop/rubocop-performance/issues/217): Fix a false positive for `Performance/RedundantEqualityComparisonBlock` when using block argument is used for an argument of `is_a`. ([@koic][])
 
 ## 1.10.0 (2021-03-01)
 

lib/rubocop/cop/performance/redundant_equality_comparison_block.rb

@@ -39,6 +39,7 @@ def on_block(node)
           block_argument = node.arguments.first
           block_body = node.body
           return unless use_equality_comparison_block?(block_body)
+          return if same_block_argument_and_is_a_argument?(block_body, block_argument)
           return unless (new_argument = new_argument(block_argument, block_body))
 
           range = offense_range(node)
@@ -55,6 +56,12 @@ def use_equality_comparison_block?(block_body)
           block_body.send_type? && COMPARISON_METHODS.include?(block_body.method_name)
         end
 
+        def same_block_argument_and_is_a_argument?(block_body, block_argument)
+          return false unless %i[is_a? kind_of?].include?(block_body.method_name)
+
+          block_argument.source == block_body.first_argument.source
+        end
+
         def new_argument(block_argument, block_body)
           if block_argument.source == block_body.receiver.source
             block_body.first_argument.source

spec/rubocop/cop/performance/redundant_equality_comparison_block_spec.rb

@@ -71,6 +71,18 @@
       RUBY
     end
 
+    it 'does not register an offense when using block argument is used for an argument of `is_a`' do
+      expect_no_offenses(<<~RUBY)
+        klasses.all? { |klass| item.is_a?(klass) }
+      RUBY
+    end
+
+    it 'does not register an offense when using block argument is used for an argument of `kind_of?`' do
+      expect_no_offenses(<<~RUBY)
+        klasses.all? { |klass| item.kind_of?(klass) }
+      RUBY
+    end
+
     it 'does not register and corrects an offense when using block argument is not used as it is' do
       expect_no_offenses(<<~RUBY)
         items.all? { |item| item.do_something == other }