withInput() doesn't work

And when I use it with withError(), it does not work either.

This works:

if ($validation->fails()) {
    //////////// Works and return the $errors array
    return redirect()->back()->withErrors($validation);                         
}

This doesn't work:

if ($validation->fails()) {
    return redirect()->back()->withInput();                         
}

This doesn't work too (either for withInput() and for withErrors())

if ($validation->fails()) {
    return redirect()->back()->withInput()->withErrors($validacion);
}

This is symptom of ... what problem?

via Chebli Mohamed