Fix an infinite loop error for Layout/EndAlignment

Fixes standardrb/standard#598.

This PR fixes an infinite loop error for `Layout/EndAlignment`
when misaligned in singleton class assignments with `EnforcedStyleAlignWith: variable`.

changelog/fix_an_error_for_layout_end_alignment.md

@@ -0,0 +1 @@
+* [#12580](https://github.com/rubocop/rubocop/pull/12580): Fix an infinite loop error for `Layout/EndAlignment` when misaligned in singleton class assignments with `EnforcedStyleAlignWith: variable`. ([@koic][])

lib/rubocop/cop/layout/end_alignment.rb

@@ -83,7 +83,11 @@ def on_class(node)
         end
 
         def on_sclass(node)
-          check_other_alignment(node)
+          if node.parent&.assignment?
+            check_asgn_alignment(node.parent, node)
+          else
+            check_other_alignment(node)
+          end
         end
 
         def on_module(node)

spec/rubocop/cli/autocorrect_spec.rb

@@ -3134,6 +3134,32 @@ class << self
     RUBY
   end
 
+  it 'corrects `Layout/EndAlignment` when `end` is not aligned with beginning of a singleton class assignment ' \
+     'and EnforcedStyleAlignWith is set to `variable` style' do
+    source_file = Pathname('example.rb')
+    create_file(source_file, <<~RUBY)
+      def thing
+        @thing ||= class << Object.new
+          end
+      end
+    RUBY
+
+    create_file('.rubocop.yml', <<~YAML)
+      Layout/EndAlignment:
+        EnforcedStyleAlignWith: variable
+    YAML
+
+    status = cli.run(%w[--autocorrect --only Layout/EndAlignment])
+    expect(status).to eq(0)
+    expect($stderr.string).to eq('')
+    expect(source_file.read).to eq(<<~RUBY)
+      def thing
+        @thing ||= class << Object.new
+        end
+      end
+    RUBY
+  end
+
   it 'corrects `Layout/EndAlignment` when `end` is not aligned with start of line ' \
      'and EnforcedStyleAlignWith is set to `start_of_line` style' do
     source_file = Pathname('example.rb')