30         Item *next {nullptr};
31         Item *prev {nullptr};
46         return head_ == nullptr;  in Empty()
57         ES2PANDA_ASSERT(item != nullptr);  in Append()
65         item->next = nullptr;  in Append()
66         item->prev = nullptr;  in Append()
81         ES2PANDA_ASSERT(item != nullptr);  in Prepend()
89         item->next = nullptr;  in Prepend()
90         item->prev = nullptr;  in Prepend()
105         ES2PANDA_ASSERT(item != nullptr);  in Insert()
114         ES2PANDA_ASSERT(after != nullptr);  in Insert()
115         ES2PANDA_ASSERT(item != nullptr);  in Insert()
123         if (afterNext != nullptr) {  in Insert()
135         ES2PANDA_ASSERT(item != nullptr);  in Erase()
139             head_ = nullptr;  in Erase()
140             tail_ = nullptr;  in Erase()
143             if (head_ != nullptr) {  in Erase()
144                 head_->prev = nullptr;  in Erase()
148             if (tail_ != nullptr) {  in Erase()
149                 tail_->next = nullptr;  in Erase()
156             ES2PANDA_ASSERT(prev != nullptr && next != nullptr);  in Erase()
161         item->next = nullptr;  in Erase()
162         item->prev = nullptr;  in Erase()
166     Item *head_ {nullptr};
167     Item *tail_ {nullptr};