How Should Nullable And Optional Properties Be Handled During Deserialization?

[jorgerangel-msft]

Discussion arose from #4850.

MGC currently follows autorest for building the deserialization method of a model. For properties that are nullable and not collections, we generate a check for the json element to see if it's value is Null and then assign the corresponding property to null. This can be redundant in most cases since properties in the method are initialized using their default value ie. int? someInt = default.

Is this check still necessary? If the spec says a property is not nullable, is there still a need for adding this check?