FlattenUnions fails when unifying an array element union that indirectly contains an intersection.

[ankrgyl]

This shows up while trying to convert the latest OpenAI specs.

Issue Type

input parsing

Context (Environment, Version, Language)

• Environment: macOS, Apple Silicon, Node.js v24.15.0
• Quicktype versions: 23.3.25 and 24.0.2
• Also reproduced on: upstream master at commit 7a86b5e1042f7bc387876fbbb0c0547d2ca22cbc
• Input language: JSON Schema draft-07
• Output language: Rust

Description

I'm trying to parse OpenAI's OpenAPI spec and create generated types

Input Data

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "input": {
      "type": "array",
      "items": {
        "oneOf": [
          { "$ref": "#/definitions/Message" },
          { "$ref": "#/definitions/Item" }
        ]
      }
    }
  },
  "definitions": {
    "Message": {
      "type": "object",
      "properties": {
        "content": { "type": "string" }
      },
      "required": ["content"]
    },
    "Item": {
      "oneOf": [
        { "$ref": "#/definitions/FunctionOutput" },
        { "$ref": "#/definitions/ReasoningItem" }
      ]
    },
    "FunctionOutput": {
      "allOf": [
        { "$ref": "#/definitions/BaseItem" },
        {
          "type": "object",
          "properties": {
            "output": { "type": "string" }
          },
          "required": ["output"]
        }
      ]
    },
    "BaseItem": {
      "type": "object",
      "properties": {
        "id": { "type": "string" }
      },
      "required": ["id"]
    },
    "ReasoningItem": {
      "type": "object",
      "properties": {
        "summary": { "type": "string" }
      },
      "required": ["summary"]
    }
  }
}

Expected Behaviour / Output

Something like

#[derive(Serialize, Deserialize)]
pub struct TopLevel {
    pub input: Option<Vec<Item>>,
}

#[derive(Serialize, Deserialize)]
pub struct Item {
    pub content: Option<String>,
    pub id: Option<String>,
    pub output: Option<String>,
    pub summary: Option<String>,
}

Current Behaviour / Output

Error: Internal error: Unknown type intersection.

Steps to Reproduce

Save the above json schema to nested-intersection.schema.json and then run

npx quicktype@24.0.2 \
  --src-lang schema \
  --lang rust \
  nested-intersection.schema.json

Possible Solution

Will send a PR