i18next: Type instantiation is excessively deep and possibly infinite

🐛 Bug Report

I’m getting the error Type instantiation is excessively deep and possibly infinite when defining CustomTypeOptions.

My type definition:

// i18next.d.ts
import resources from "../i18n/locales/resources";

declare module "i18next" {
	interface CustomTypeOptions {
		returnNull: false;
		resources: typeof resources['en'];
	}
}

where resources are:

// i18n/locales/resources
import definitions_de from './definitions/de.json';
import definitions_en from './definitions/en.json';
import errors_de from './errors/de.json';
import errors_en from './errors/en.json';

export const resources = {
	de: {
		definitions: definitions_de,
		errors: errors_de,
	},
	en: {
		definitions: definitions_en,
		errors: errors_en,
	},
<etc.>
}

In my code, I’m doing:

// src/myCode
const t = i18nInstance.getFixedT(this.locale as Locale);

throw new Error(t('index.edgeError'));

Expected behavior

I would expect the type definition to work. And the code to compile. However, while I don’t get any tslint errors, my tests are failing with the error Type instantiation is excessively deep and possibly infinite, which also shows up (sometimes) in VS Code.

Your Environment

• runtime version: node16
• i18next version: “^22.4.10”, “typescript”: “^4.9.5”,
• os: Mac