Fix exception on Lint/InheritException when class definition has non-constant siblings

changelog/fix_error_for_lint_exception.md

@@ -0,0 +1 @@
+* [#11930](https://github.com/rubocop/rubocop/pull/11930): Fix exception on `Lint/InheritException` when class definition has non-constant siblings. ([@rafaelfranca][])

lib/rubocop/cop/lint/inherit_exception.rb

@@ -91,7 +91,9 @@ def exception_class?(class_node)
         def inherit_exception_class_with_omitted_namespace?(class_node)
           return false if class_node.parent_class.namespace&.cbase_type?
 
-          class_node.left_siblings.any? { |sibling| exception_class?(sibling.identifier) }
+          class_node.left_siblings.any? do |sibling|
+            sibling.respond_to?(:identifier) && exception_class?(sibling.identifier)
+          end
         end
 
         def preferred_base_class

spec/rubocop/cop/lint/inherit_exception_spec.rb

@@ -48,6 +48,29 @@ class Exception < RuntimeError; end
         end
       end
 
+      context 'when inheriting `Exception` and has non-constant siblings' do
+        it 'registers an offense and corrects' do
+          expect_offense(<<~RUBY)
+            module Foo
+              include Bar
+
+              class C < Exception; end # This `Exception` is the same as `::Exception`.
+                        ^^^^^^^^^ Inherit from `RuntimeError` instead of `Exception`.
+              class Exception < RuntimeError; end
+            end
+          RUBY
+
+          expect_correction(<<~RUBY)
+            module Foo
+              include Bar
+
+              class C < RuntimeError; end # This `Exception` is the same as `::Exception`.
+              class Exception < RuntimeError; end
+            end
+          RUBY
+        end
+      end
+
       context 'when inheriting `::Exception`' do
         it 'registers an offense and corrects' do
           expect_offense(<<~RUBY)