请教一个 leetcode 上 Swift 语法展开问题

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public var val: Int
 *     public var next: ListNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.next = nil
 *     }
 * }
 */
class Solution {
    func reverseList(_ head: ListNode?) -> ListNode? {
        var rev: ListNode? = nil, head = head
        while head != nil
        {
            (head, rev, head!.next) = (head!.next, head, rev)   //请问下这段展开表达式
        }
        return rev
    }
}

请问下如上标记那段的展开表达式是什么？