Merge pull request #27787 from y-yagi/show_correct_class_name_in_migration_error

show correct class name in migration inherited directly error

activerecord/lib/active_record/migration.rb

@@ -525,7 +525,7 @@ def self.inherited(subclass) # :nodoc:
         raise StandardError, "Directly inheriting from ActiveRecord::Migration is not supported. " \
           "Please specify the Rails release the migration was written for:\n" \
           "\n" \
-          "  class #{self.class.name} < ActiveRecord::Migration[4.2]"
+          "  class #{subclass} < ActiveRecord::Migration[4.2]"
       end
     end
 

activerecord/test/cases/migration/compatibility_test.rb

@@ -103,9 +103,10 @@ def migrate(x)
       end
 
       def test_legacy_migrations_raises_exception_when_inherited
-        assert_raises(StandardError) do
-          Class.new(ActiveRecord::Migration)
+        e = assert_raises(StandardError) do
+          class_eval("class LegacyMigration < ActiveRecord::Migration; end")
         end
+        assert_match(/LegacyMigration < ActiveRecord::Migration\[4\.2\]/, e.message)
       end
     end
   end