This is expected because the rule is not type-aware. We'd need to build an extension rule.

This is a pretty rare usecase so I'm not sure if it makes sense for us to own and maintain an extension rule for it.

This is the first time in the history of the project that someone has requested this behaviour - so it's either not a common pattern, or just not a common pattern in codebases that use the rule.

The closest issue we've had filed is #3455 (which is similar but A LOT more complicated).

I'll leave this as "evaluating community engagement", but my gut is that we probably won't action this due to how rare it is.

Totally fair. I hadn't see #3455 when I searched, but I'd be okay if you want to close this as duplicate of that.

To add some missed details:

• I had a vague expectation that "plugin:@typescript-eslint/eslint-recommended" would have disabled/adjusted the failing eslint rule in some way to work around this
• The main reason I think this is an actually problem is because ts itself actually warns about the break statement I need to add (typescript itself actually conflicts with eslint directly here). If I had stricter typescript compiler warning requirements in my PR checks I'd be forced to actually disable a linting rule.
  

Yeah for sure - your want makes sense because there's no way to satisfy the lint rule and TS at the same time with code when using this pattern.

But you can satisfy the rule by adding a comment. By default the rule will ignore cases when there is a comment that matches the regex /falls?\s*through/.

I.e. you can add the comment // impossible to fall through due to the above assertion function, and the rule would not error playground.

But this is obviously sub-par in comparison to the rule just working.

@bradzacher fwiw I was just about to file this bug as well, thereby making it half as rare now 🙂

In Next.js there are e.g. redirect("/path") and notFound() which return never. I think this issue affects those cases quite a lot. For example:

function getUserType(): "unauthorized" | "normal" | "admin" {
  return "normal";
}

export default function MyPage() {
  const userType = getUserType();

  switch (userType) {
    case "unauthorized":
      redirect("/login");
      break; // <-- problem here
    case "normal":
      return <div>Welcome, user</div>;
    case "admin":
      return <div>Welcome, admin</div>;
  }
}

With break;:

Without break;:

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@Eldemarkki your case is easily satisfiable by prefixing it with return

This has the added benefit of also making it very clear that redirect terminates things - which is nice for newbies and when working without intellisense (eg gh reviews)

Duplicate of #3455