Fix an incorrect auto-correct for Layout/ClassStructure

This PR fixes the following incorrect auto-correct for `Layout/ClassStructure`
when heredoc constant is defined after public method.

```console
% cat example.rb
class Foo
  def foo
  end

  CONSTANT = <<~EOS.freeze
    str
  EOS
end

% bundle exec rubocop --only Layout/ClassStructure -a
(snip)

% cat example.rb
class Foo
  CONSTANT = <<~EOS.freeze
  def foo
  end

    str
  EOS
end
```

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 * [#8892](https://github.com/rubocop-hq/rubocop/issues/8892): Fix an error for `Style/StringConcatenation` when correcting nested concatenable parts. ([@fatkodima][])
 * [#8781](https://github.com/rubocop-hq/rubocop/issues/8781): Fix handling of comments in `Style/SafeNavigation` autocorrection. ([@dvandersluis][])
+* [#8907](https://github.com/rubocop-hq/rubocop/pull/8907): Fix an incorrect auto-correct for `Layout/ClassStructure` when heredoc constant is defined after public method. ([@koic][])
 
 ### Changes
 

lib/rubocop/cop/layout/class_structure.rb

@@ -265,6 +265,9 @@ def source_range_with_comment(node)
         end
 
         def end_position_for(node)
+          heredoc = find_heredoc(node)
+          return heredoc.location.heredoc_end.end_pos + 1 if heredoc
+
           end_line = buffer.line_for_position(node.loc.expression.end_pos)
           buffer.line_range(end_line).end_pos
         end
@@ -284,6 +287,10 @@ def start_line_position(node)
           buffer.line_range(node.loc.line).begin_pos - 1
         end
 
+        def find_heredoc(node)
+          node.each_node(:str, :dstr, :xstr).find(&:heredoc?)
+        end
+
         def buffer
           processed_source.buffer
         end

spec/rubocop/cop/layout/class_structure_spec.rb

@@ -214,4 +214,79 @@ class Foo
       end
     end
   end
+
+  it 'registers an offense and corrects when str heredoc constant is defined after public method' do
+    expect_offense(<<~RUBY)
+      class Foo
+        def do_something
+        end
+
+        CONSTANT = <<~EOS
+        ^^^^^^^^^^^^^^^^^ `constants` is supposed to appear before `public_methods`.
+          str
+        EOS
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      class Foo
+        CONSTANT = <<~EOS
+          str
+        EOS
+
+        def do_something
+        end
+      end
+    RUBY
+  end
+
+  it 'registers an offense and corrects when dstr heredoc constant is defined after public method' do
+    expect_offense(<<~'RUBY')
+      class Foo
+        def do_something
+        end
+
+        CONSTANT = <<~EOS
+        ^^^^^^^^^^^^^^^^^ `constants` is supposed to appear before `public_methods`.
+          #{str}
+        EOS
+      end
+    RUBY
+
+    expect_correction(<<~'RUBY')
+      class Foo
+        CONSTANT = <<~EOS
+          #{str}
+        EOS
+
+        def do_something
+        end
+      end
+    RUBY
+  end
+
+  it 'registers an offense and corrects when xstr heredoc constant is defined after public method' do
+    expect_offense(<<~'RUBY')
+      class Foo
+        def do_something
+        end
+
+        CONSTANT = <<~`EOS`
+        ^^^^^^^^^^^^^^^^^^^ `constants` is supposed to appear before `public_methods`.
+          str
+        EOS
+      end
+    RUBY
+
+    expect_correction(<<~'RUBY')
+      class Foo
+        CONSTANT = <<~`EOS`
+          str
+        EOS
+
+        def do_something
+        end
+      end
+    RUBY
+  end
 end