Generic parameter 'ResultType' could not be inferred

Question

So after migrating my code to Swift 3 I now get errors with the following code designed to remove all data from Core Data. I have seen similar posts about this issue but none that seem to apply directly to how the code below works where I define the NSFetchRequest() without any parameters.

func removeAllChargerData(){
    // Remove all charging data from persistent storage
    let fetchRequest = NSFetchRequest()
    let entity = NSEntityDescription.entity(forEntityName: "ChargerPrimary", in: self.secondMoc)
    fetchRequest.entity = entity
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)

    do {
        try self.secondMoc.execute(deleteRequest)
    } catch {
        let deleteError = error as NSError
        NSLog("\(deleteError), \(deleteError.localizedDescription)")
    }

}

It now throws an error on the let fetchRequest line stating: Generic parameter 'ResultType' could not be inferred.

Could someone explain what's changed here and how best to go about fixing it?

Thanks!