Cannot use different type for HTTP 404.

I want to use progenitor, but generated client uses same response type for HTTP 404 as it has for HTTP 200.

Here is the most simple reproducible spec:

openapi: "3.0.2"
info:
  title: Demo That Triggers It
  version: 0.1.0
  description: "Here you go"
  contact:
    name: Demo
servers:
  - url: http://localhost:12346/
paths:
  /items/{key}:
    get:
      summary: get_state_element
      operationId: get_state_element
      tags: [ "hi-there" ]
      parameters:
        - name: key
          in: path
          required: true
          schema:
            type: string
      responses:
        200:
          $ref: "#/components/responses/StateMapElementResponse2"
        404:
          "$ref": "#/components/responses/NotFound"
components:
  parameters:
    rollup_height:
      name: rollup_height
      in: query
      description: The height of the rollup to query. If not provided, the rollup head is used.
      required: false
      schema:
        type: integer
        minimum: 0
  responses:
    StateMapElementResponse2:
      description: Response containing the value of a `StateMap` element.
      content:
        application/json:
          schema:
            type: object
            properties:
              data:
                type: object
                properties:
                  key:
                    $ref: "#/components/schemas/AnyJsonValue"
                  value:
                    $ref: "#/components/schemas/AnyJsonValue"
                required:
                  - key
                  - value
              meta:
                $ref: "#/components/schemas/AnyJsonValue"
            required:
              - data
    NotFound:
      description: The requested resource was not found.
      content:
        application/json:
          schema:
            type: object
            properties:
              errors:
                type: array
                items:
                  $ref: "#/components/schemas/Error"
              meta:
                $ref: "#/components/schemas/AnyJsonValue"
            required:
              - errors
  schemas:
    AnyJsonValue:
      description: "Any JSON type, including null."
      nullable: true
      oneOf:
        - type: string
          title: "String"
        - type: number
          title: "Number"
        - type: boolean
          title: "Boolean"
        - type: array
          title: "Array"
          items:
            x-stainless-any: true
        - type: object
          title: "Object"
          additionalProperties: true
    Error:
      type: object
      properties:
        status:
          type: integer
          format: int32
          description: HTTP status code related to this error
        title:
          type: string
        details:
          $ref: "#/components/schemas/AnyJsonValue"
      required:
        - status
        - title
        - details

Here is part of the codegen.rs:

impl Client {
    pub async fn get_state_element<'a>(
        &'a self,
        key: &'a str,
    ) -> Result<
        ResponseValue<types::GetStateElementResponse>,
        Error<types::GetStateElementResponse>,
    > { todo!("omitted"); }
}    

I am struggling to find what causes the problem, that Error variant is the same as success.

Start with codegen.rs and generate a client from the minimal OpenAPI spec in the issue, focusing on how the 200 and 404 responses are represented. Done means the generated get_state_element method distinguishes the 404 response type from the 200 response type; no specific test file is named in the issue.