41     assert(!tail_);  in ~LRUList()
52     assert((!head_ && !tail_) || (head_ && tail_));  in Push()
54     assert(!tail_ || !tail_->next_);  in Push()
62     if (!tail_) {  in Push()
63       tail_ = t;  in Push()
77     assert(tail_ && head_);  in Pop()
78     assert(!tail_->next_);  in Pop()
108     return !head_ && !tail_;  in IsEmpty()
118     assert(head_ && tail_);  in UnlinkImpl()
120     assert(t->next_ || tail_ == t);  in UnlinkImpl()
129     if (tail_ == t) {  in UnlinkImpl()
130       tail_ = tail_->prev_;  in UnlinkImpl()
152     assert((!head_ && !tail_) || (head_ && tail_));  in PushBackImpl()
154     assert(!tail_ || !tail_->next_);  in PushBackImpl()
156     t->prev_ = tail_;  in PushBackImpl()
157     if (tail_) {  in PushBackImpl()
158       tail_->next_ = t;  in PushBackImpl()
161     tail_ = t;  in PushBackImpl()
163       head_ = tail_;  in PushBackImpl()
169   T* tail_ = nullptr;         // back (hot)  variable