[BUG] [dart-dio-next] Custom Date type has no replace method

Description

In yaml definition I have a class with a property like this:

absentFrom:
        $ref: '#/definitions/Date'

and below is Date definition as

Date:
    type: object
    required:
      - year
      - month
      - day
    properties:
      year:
        type: integer
        format: int32
      month:
        type: integer
        format: int32
      day:
        type: integer
        format: int32

Generator creates code that relies on autogenerated Date type's replace method which does not exist.

case r'absentFrom':
          final valueDes = serializers.deserialize(value,
              specifiedType: const FullType(Date)) as Date;
          result.absentFrom.replace(valueDes);
          break;

The problem is that there is no replace method on dart's Date type, at least so it seems.

openapi-generator version

5.2.1, 6.0.0

OpenAPI declaration file content or url

Full model

SchoolAbsenceDay:
    type: object
    required:
      - year
      - month
      - day
    properties:
      year:
        type: integer
        format: int32
      month:
        type: integer
        format: int32
      day:
        type: integer
        format: int32
      absentFrom:
        $ref: '#/definitions/Date'
      absentTo:
        $ref: '#/definitions/Date'
      schoolType:
        type: string
      school:
        type: string
      personType:
        type: string
      personClass:
        type: string
      reason:
        type: string
  Date:
    type: object
    required:
      - year
      - month
      - day
    properties:
      year:
        type: integer
        format: int32
      month:
        type: integer
        format: int32
      day:
        type: integer
        format: int32

Generation Details

˙... -g dart-dio-next -c open-generator-config.yaml --enable-post-process-file
dart-dio yields same result

Steps to reproduce

Generate dart-dio-next code from

Suggest a fix

Deserialization should create a new Date instance instead of using replace method.

Reproduce the issue with the supplied OpenAPI definitions using the dart-dio-next generator command, then inspect the generated Dart deserialization for SchoolAbsenceDay and the custom Date model. Confirm the generated code does not call a missing replace method and that the resulting client code compiles and handles the Date reference correctly.