Incompatible types with array of ObjectId after upgrading to 6.0.1

[pqvst]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
Creating a schema with an array of ObjectId and defining a corresponding TypeScript interface causes a compiler error, stating that the types are incompatible.

A single ObjectId (no array) works fine though. Arrays of other types also work fine. It just seems to be array of ObjectId which is problematic.

If the current behavior is a bug, please provide the steps to reproduce.

import { Schema, model, ObjectId, Document } from 'mongoose';

interface Foo extends Document<ObjectId> {
  arrayOfObjectId: ObjectId[];
}

const fooSchema = new Schema<Foo>({
  arrayOfObjectId: { type: [Schema.Types.ObjectId], required: true },
});

tsconfig.json

{
  "compilerOptions": {
    "outDir": "./build",
    "allowJs": true,
    "target": "ES2018",
    "module": "CommonJS",
    "sourceMap": true,
    "esModuleInterop": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "typeRoots": [
      "types", // must be first!
      "node_modules/@types"
    ]
  }
}

What is the expected behavior?
Before upgrading to mongoose v6 I was able to create a schema with an array of ObjectId and use a corresponding TypeScript interface.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
node: v16.3.0
mongoose: 6.0.1

[vkarpov15]

This appears to be fixed by the fix for #10605