Fix false negatives for Style/RedundantReturn

changelog/fix_false_negative_for_style_redundant_return.md

@@ -0,0 +1 @@
+* [#12674](https://github.com/rubocop/rubocop/pull/12674): Fix false negatives for `Style/RedundantReturn` when using pattern matching. ([@koic][])

lib/rubocop/cop/style/redundant_return.rb

@@ -113,6 +113,7 @@ def check_branch(node)
           case node.type
           when :return then check_return_node(node)
           when :case   then check_case_node(node)
+          when :case_match then check_case_match_node(node)
           when :if     then check_if_node(node)
           when :rescue then check_rescue_node(node)
           when :resbody then check_resbody_node(node)
@@ -140,6 +141,11 @@ def check_case_node(node)
           check_branch(node.else_branch)
         end
 
+        def check_case_match_node(node)
+          node.in_pattern_branches.each { |in_pattern_node| check_branch(in_pattern_node.body) }
+          check_branch(node.else_branch)
+        end
+
         def check_if_node(node)
           return if node.ternary?
 

spec/rubocop/cop/style/redundant_return_spec.rb

@@ -601,4 +601,52 @@ def func
       RUBY
     end
   end
+
+  context 'when return is inside a in-branch' do
+    it 'registers an offense and autocorrects' do
+      expect_offense(<<~RUBY)
+        def func
+          some_preceding_statements
+          case x
+          in y then return 1
+                    ^^^^^^ Redundant `return` detected.
+          in z then return 2
+                    ^^^^^^ Redundant `return` detected.
+          in q
+          else
+            return 3
+            ^^^^^^ Redundant `return` detected.
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        def func
+          some_preceding_statements
+          case x
+          in y then 1
+          in z then 2
+          in q
+          else
+            3
+          end
+        end
+      RUBY
+    end
+  end
+
+  context 'when case match nodes are empty' do
+    it 'accepts empty in nodes' do
+      expect_no_offenses(<<~RUBY)
+        def func
+          case x
+          in y then 1
+          in z # do nothing
+          else
+            3
+          end
+        end
+      RUBY
+    end
+  end
 end