Polymorphic schema with 'useNativeEnums' leads to 'never' enum discriminator field

[MGabr]

What are the steps to reproduce this issue?

1. Add a api-docs.yaml spec with a polymorphic schema :

   openapi: 3.0.1
   info:
     title: OpenAPI definition
     version: v0
   servers:
     - url: http://localhost:8080
       description: Generated server url
   paths:
     /pet:
       get:
         tags:
           - pet-controller
         operationId: getPet
         responses:
           "200":
             description: OK
             content:
               '*/*':
                 schema:
                   $ref: "#/components/schemas/Pet"
   components:
     schemas:
       Cat:
         required:
           - type
         type: object
         allOf:
           - $ref: "#/components/schemas/Pet"
           - type: object
             properties:
               lives:
                 type: integer
                 format: int32
       Dog:
         required:
           - type
         type: object
         allOf:
           - $ref: "#/components/schemas/Pet"
           - type: object
             properties:
               age:
                 type: integer
                 format: int32
       Pet:
         required:
           - type
         type: object
         properties:
           type:
             type: string
             enum:
               - DOG
               - CAT
         discriminator:
           propertyName: type
           mapping:
             DOG: "#/components/schemas/Dog"
             CAT: "#/components/schemas/Cat"

2. Add a config orval.config.js with useNativeEnums: true

    module.exports = {
      'api-docs-file': {
        input: './api-docs.yaml',
        output: {
          target: './api-orval.ts',
          override: {
            useNativeEnums: true,
          }
        }
      },
    };

3. Generate types with orval --config orval.config.js.

4. Add a TypeScript file api-orval-types-test.ts that uses the types:

   import {Dog, DogType} from './api-orval';
   
   const dog: Dog = {
       type: DogType.DOG,
       age: 7,
   };

5. Run tsc api-orval.ts api-orval-types-test.ts

What happens?

The following model gets generated:

export enum PetType {
  DOG= 'DOG',
  CAT= 'CAT',
}

export interface Pet {
  type: PetType;
}

export enum DogType {
  DOG= 'DOG',
}

export type DogAllOf = {
  age?: number;
};

export type Dog = Pet & DogAllOf & {
  type: DogType;
};

So there are two different types for the type field of Dog. PetType for Pet and DogType for Dog.

This leads to the following TypeScript errors:

Type 'import("api-orval").DogType' is not assignable to type 'never'.
Type 'number' is not assignable to type 'never'.

What were you expecting to happen?

No TypeScript errors.

Types like the following being generated:

export enum PetType {
  DOG= 'DOG',
  CAT= 'CAT',
}

export interface Pet {
  type: PetType;
}

export type DogAllOf = {
  age?: number;
};

export type Dog = Pet & DogAllOf & {
  type: PetType.DOG;
};

What versions are you using?

  System:
    OS: Windows 11 10.0.26100
    CPU: (12) x64 AMD Ryzen 5 3600X 6-Core Processor
    Memory: 17.26 GB / 31.95 GB
  npmPackages:
    axios: ^1.7.7 => 1.7.7
    orval: ^7.1.1 => 7.1.1
    typescript: ^5.6.2 => 5.6.2