[Fix #9627] Fix an incorrect auto-correct for Style/StructInheritance

Fixes #9627.

This PR fixes an incorrect auto-correct for `Style/StructInheritance` when
extending instance of Struct without `do` ... `end` and class body is empty.

changelog/fix_an_incorrect_autocorrect_for_style_struct_inheritance.md

@@ -0,0 +1 @@
+* [#9627](https://github.com/rubocop/rubocop/issues/9627): Fix an incorrect auto-correct for `Style/StructInheritance` when extending instance of Struct without `do` ... `end` and class body is empty. ([@koic][])

lib/rubocop/cop/style/struct_inheritance.rb

@@ -48,6 +48,8 @@ def on_class(node)
         def correct_parent(parent, corrector)
           if parent.block_type?
             corrector.remove(range_with_surrounding_space(range: parent.loc.end, newlines: false))
+          elsif (class_node = parent.parent).body.nil?
+            corrector.remove(range_by_whole_lines(class_node.loc.end, include_final_newline: true))
           else
             corrector.insert_after(parent.loc.expression, ' do')
           end

spec/rubocop/cop/style/struct_inheritance_spec.rb

@@ -44,6 +44,18 @@ class Person < Struct.new(:first_name, :last_name) do end
     RUBY
   end
 
+  it 'registers an offense when extending instance of Struct without `do` ... `end` and class body is empty' do
+    expect_offense(<<~RUBY)
+      class Person < Struct.new(:first_name, :last_name)
+                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't extend an instance initialized by `Struct.new`. Use a block to customize the struct.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      Person = Struct.new(:first_name, :last_name)
+    RUBY
+  end
+
   it 'registers an offense when extending instance of ::Struct with ' \
      'do ... end' do
     expect_offense(<<~RUBY)