[Fix rubocop#162] Fix a false positive for `Performance/RedundantBloc…

…kCall`

Fixes rubocop#162.

This PR fixes a false positive for `Performance/RedundantBlockCall`
when an optional block that is overridden by block variable.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#162](https://github.com/rubocop/rubocop-performance/issues/162): Fix a false positive for `Performance/RedundantBlockCall` when an optional block that is overridden by block variable. ([@koic][])
+
 ## 1.10.1 (2021-03-02)
 
 ### Bug fixes

lib/rubocop/cop/performance/redundant_block_call.rb

@@ -78,7 +78,7 @@ def autocorrect(corrector, node)
         end
 
         def calls_to_report(argname, body)
-          return [] if blockarg_assigned?(body, argname)
+          return [] if blockarg_assigned?(body, argname) || shadowed_block_argument?(body, argname)
 
           blockarg_calls(body, argname).map do |call|
             return [] if args_include_block_pass?(call)
@@ -87,6 +87,12 @@ def calls_to_report(argname, body)
           end
         end
 
+        def shadowed_block_argument?(body, block_argument_of_method_signature)
+          return false unless body.block_type?
+
+          body.arguments.map(&:source).include?(block_argument_of_method_signature.to_s)
+        end
+
         def args_include_block_pass?(blockcall)
           _receiver, _call, *args = *blockcall
 

spec/rubocop/cop/performance/redundant_block_call_spec.rb

@@ -117,7 +117,7 @@ def method(&block)
     RUBY
   end
 
-  it 'accepts an optional block that is overridden' do
+  it 'accepts an optional block that is overridden by local variable' do
     expect_no_offenses(<<~RUBY)
       def method(&block)
         block = ->(i) { puts i }
@@ -126,6 +126,35 @@ def method(&block)
     RUBY
   end
 
+  it 'accepts an optional block that is overridden by block variable' do
+    expect_no_offenses(<<~RUBY)
+      def method(&block)
+        ->(i) { puts i }.then do |block|
+          block.call(1)
+        end
+      end
+    RUBY
+  end
+
+  it 'registers an offense when an optional block that is not overridden by block variable' do
+    expect_offense(<<~RUBY)
+      def method(&block)
+        ->(i) { puts i }.then do |_block|
+          block.call(1)
+          ^^^^^^^^^^^^^ Use `yield` instead of `block.call`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      def method(&block)
+        ->(i) { puts i }.then do |_block|
+          yield(1)
+        end
+      end
+    RUBY
+  end
+
   it 'formats the error message for func.call(1) correctly' do
     expect_offense(<<~RUBY)
       def method(&func)