Revert "Merge pull request rails#48406 from rails/revert-46790-singular-association-refactor"

This reverts commit f6f2b2d, reversing
changes made to 3e01b26.

Author: byroot

activerecord/lib/active_record/associations/has_one_association.rb

@@ -92,6 +92,10 @@ def set_new_record(record)
           replace(record, false)
         end
 
+        def replace_keys(record, force: false)
+          # Has one association doesn't have foreign keys to replace.
+        end
+
         def remove_target!(method)
           case method
           when :delete

activerecord/lib/active_record/associations/singular_association.rb

@@ -57,7 +57,7 @@ def _create_record(attributes, raise_error = false, &block)
           reflection.klass.transaction do
             record = build(attributes, &block)
             saved = record.save
-            set_new_record(record)
+            replace_keys(record, force: true)
             raise RecordInvalid.new(record) if !saved && raise_error
             record
           end