If the return type of saga select becomes undefined when you upgrade to TypeScript 3.6.3
const editingEntry: EditingEntry = yield select(editingEntrySelector); // type is undefined. not EditingEntry
const entry = validateEntry(editingEntry); // compile error.
To fix
Update react-saga to 1.1.1 https://github.com/redux-saga/redux-saga/releases/tag/v1.1.1