Merge pull request #321 from koic/fix_a_false_positive_for_performanc…

…e_sum

Fix a false positive for `Performance/Sum`

changelog/fix_a_false_positive_for_performance_sum.md

@@ -0,0 +1 @@
+* [#321](https://github.com/rubocop/rubocop-performance/pull/321): Fix a false positive for `Performance/Sum` when using `TargetRubyVersion` is 2.3 or lower. ([@koic][])

lib/rubocop/cop/performance/sum.rb

@@ -70,6 +70,9 @@ module Performance
       class Sum < Base
         include RangeHelp
         extend AutoCorrector
+        extend TargetRubyVersion
+
+        minimum_target_ruby_version 2.4
 
         MSG = 'Use `%<good_method>s` instead of `%<bad_method>s`.'
         MSG_IF_NO_INIT_VALUE =

spec/rubocop/cop/performance/sum_spec.rb

@@ -304,6 +304,14 @@
         array.sum
       RUBY
     end
+
+    context 'when Ruby 2.3 or lower', :ruby23 do
+      it "does not register an offense when using `array.#{method}(10, :+)`" do
+        expect_no_offenses(<<~RUBY, method: method)
+          array.#{method}(10, :+)
+        RUBY
+      end
+    end
   end
 
   %i[map collect].each do |method|