Variable "$foo" is propably undefined when using ->when() function on eloquent. about larastan HOT 2 OPEN

That's because you're accessing the $ids from the outer scope which hasn't has the isset applied to it (from static analysis standpoint).

First use a null default value, and then use the $ids that is passed to the closure:

$ids = null;

if ($user->is_admin) {
     $ids = Position::pluck('id')
}

InvoiceableItem::query()
   ->when($ids, fn($query, $ids) => $query->whereIn('position_id', $ids))
   ->get();

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$ids = $user->is_admin
    ? Position::pluck('id')
    : [];

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