Hello,

First, thanks for the great work on Biome. I’m currently using it in a JavaScript project and really appreciate how fast, helpful it is et les suggestions de correction.

I’d like to suggest a feature that could improve code safety when working with async functions or class methods.

Use case

In my project, I often work with async functions and methods inside classes. Sometimes, a function is expected to return a value, but due to oversight, it ends up not returning anything (implicit undefined).

Problem

class UserService {
  async getUser(id) {
    if (!id) {
      return; // ❌ returns undefined
    }

    const user = await db.findUser(id);

    if (user) {
      return user;
    }

    // ❌ implicitly returns undefined
  }
}

This is a simplified example to demonstrate the problem, but such a rule could help make code safer by catching unintended undefined returns.

Thank you for taking the time to read my suggestion !