Microsoft/TypeScript
Vedi su GitHubswitch (typeof something) isn't seen as exhaustive
Open
#56.786 aperta il 14 dic 2023
Domain: check: Control FlowHelp WantedPossible Improvement
Metriche repository
- Star
- (48.455 star)
- Metriche merge PR
- (Merge medio 6g 17h) (9 PR mergiate in 30 g)
Descrizione
🔎 Search Terms
- typeof
- switch
- narrow
- type guard
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about Type Guards
⏯ Playground Link
💻 Code
function checkAll<T>(something: T): T {
switch (typeof something) {
case "number":
case "bigint":
case "boolean":
case "symbol":
case "undefined":
case "function":
case "object":
case "string":
return something;
}
}
🙁 Actual behavior
This emits the TS error: "Function lacks ending return statement and return type does not include 'undefined'.(2366)"
🙂 Expected behavior
No error, since all possible results of typeof are handled.
Additional information about the issue
It seems to only be an issue when the function argument is generic. It works if I switch the return type and parameter types to any, but I'm not sure that's a fair comparison.