[Fix #12542] Fix false positive for Lint/MixedRegexpCaptureTypes

changelog/fix_false_positive_for_lint_mixed_regexp_capture_types.md

@@ -0,0 +1 @@
+* [#12542](https://github.com/rubocop/rubocop/issues/12542): Fix false positive for `Lint/MixedRegexpCaptureTypes` when using look-ahead matcher. ([@marocchino][])

lib/rubocop/ext/regexp_node.rb

@@ -54,17 +54,22 @@ def each_capture(named: ANY)
         return enum_for(__method__, named: named) unless block_given?
 
         parsed_tree&.traverse do |event, exp, _index|
-          yield(exp) if event == :enter &&
-                        named == exp.respond_to?(:name) &&
-                        exp.respond_to?(:capturing?) &&
-                        exp.capturing?
+          yield(exp) if named_capturing?(exp, event, named)
         end
 
         self
       end
 
       private
 
+      def named_capturing?(exp, event, named)
+        event == :enter &&
+          named == exp.respond_to?(:name) &&
+          !exp.text.start_with?('(?<=') &&
+          exp.respond_to?(:capturing?) &&
+          exp.capturing?
+      end
+
       def with_interpolations_blanked
         # Ignore the trailing regopt node
         children[0...-1].map do |child|

spec/rubocop/cop/lint/mixed_regexp_capture_types_spec.rb

@@ -14,6 +14,12 @@
     RUBY
   end
 
+  it 'does not register offense to a regexp with look behind' do
+    expect_no_offenses(<<~RUBY)
+      /(?<=>)(<br>)(?=><)/
+    RUBY
+  end
+
   it 'does not register offense to a regexp with numbered capture only' do
     expect_no_offenses(<<~RUBY)
       /(foo)(bar)/