Typing of `ValidationError`'s `errors` property is incomplete

[thiagokisaki]

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

What is the current behavior?
Current type:

(property) Error.ValidationError.errors: {
  [path: string]: mongoose.Error.ValidatorError | mongoose.Error.CastError;
}

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

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: { type: String, required: true },
  address: new mongoose.Schema({ city: { type: String, required: true } }),
});

const User = mongoose.model('User', userSchema);

const user = new User({ name: {}, address: {} });

const error = user.validateSync();

// The errors property contains instances of CastError, ValidatorError and ValidationError
if (error instanceof mongoose.Error.ValidationError) {
  console.log(error.errors.name instanceof mongoose.Error.CastError); // true
  console.log(error.errors['address.city'] instanceof mongoose.Error.ValidatorError); // true
  console.log(error.errors.address instanceof mongoose.Error.ValidationError); // true
}

What is the expected behavior?
Expected type:

(property) Error.ValidationError.errors: {
  [path: string]: mongoose.Error.ValidatorError | mongoose.Error.CastError | mongoose.Error.ValidationError;
}

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
Node.js: 14.17.0
Mongoose: 5.12.12
MongoDB: 4.4.6