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• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Link to the rule's documentation

https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/switch-exhaustiveness-check.md

Description

#3616 (comment)

This comment was never implemented. The case that is not possible to detect is case 1 from the original thread

This should throw an error because all cases are not enumerated (despite there being a fallthrough).

Fail

declare const literal: "a" | "b";

switch (literal) {
  case "a": break;
  default: break;
}

Pass

declare const literal: "a" | "b";

// Valid
switch (literal) {
  case "a": break;
  case "b": break;
}

// Valid
switch (literal) {
  case "a": break;
  case "b": break;
  default: break;
}

Additional Info

Why is this useful? Say you want to define explicit behavior for each enum value. I then add an enum value to my type. Having an error in this case will be an extra catch that will allow me to ensure that I remember to update the switch statements. Essentially I want to be able to always define behavior for known types.