Bug: Dependencies Array shows missing dependency error for generic type parameters

[mrousavy]

React version: 16.13.1

Steps To Reproduce

1. Create function with generic type parameter
2. Use that generic type parameter in useCallback, useEffect or useMemo

Example:

export function useDocument<TDocument>(path: string, defaultValue: TDocument | undefined = undefined): TDocument | undefined {
	const [value, setValue] = useState<TDocument | undefined>(defaultValue);

	const onNext = useCallback((snapshot: FirebaseFirestoreTypes.DocumentSnapshot<FirebaseFirestoreTypes.DocumentData>) => {
		if (snapshot.exists) setValue(build<TDocument>(snapshot.data(), snapshot.id));
		else setValue(undefined);
	}, []);


	useEffect(() => firestore().doc(path).onSnapshot(onNext), [onNext, path]);

	return value;
}

The current behavior

Shows error React Hook useCallback has a missing dependency: 'TDocument'. Either include it or remove the dependency array.eslintreact-hooks/exhaustive-deps)

The expected behavior

Should not show any errors, because it isn't possible to add types to the dependencies array (types don't exist at runtime!)

[dsgkirkby]

I'm also seeing this issue. It only happens after updating typescript-eslint from v3.8 to v4.1.

[mrousavy]

@dsgkirkby yep, might be a typescript 4.0 problem

[eps1lon]

Duplicate of #19742. It should be fixed by #19751. We'll just need to wait for a release.

[gaearon]

[email protected] should have the fix.