Make LRUCache more like a normal container

mlx/backend/cuda/lru_cache.h

@@ -16,8 +16,9 @@ class LRUCache {
  public:
   using value_type = std::pair<K, V>;
   using list_type = std::list<value_type>;
-  using list_iter = typename list_type::iterator;
-  using map_type = M<K, list_iter>;
+  using iterator = typename list_type::iterator;
+  using const_iterator = typename list_type::const_iterator;
+  using map_type = M<K, iterator>;
 
   explicit LRUCache(size_t capacity) : capacity_(capacity) {}
 
@@ -36,16 +37,16 @@ class LRUCache {
     trim();
   }
 
-  auto begin() {
+  iterator begin() {
     return vlist_.begin();
   }
-  auto begin() const {
+  const_iterator begin() const {
     return vlist_.begin();
   }
-  auto end() {
+  iterator end() {
     return vlist_.end();
   }
-  auto end() const {
+  const_iterator end() const {
     return vlist_.end();
   }
 
@@ -54,7 +55,7 @@ class LRUCache {
     vlist_.clear();
   }
 
-  list_iter find(const K& key) {
+  iterator find(const K& key) {
     auto it = map_.find(key);
     if (it == map_.end())
       return end();
@@ -62,14 +63,15 @@ class LRUCache {
     return it->second;
   }
 
-  std::pair<list_iter, bool> emplace(const K& key, V value) {
+  template <typename U>
+  std::pair<iterator, bool> emplace(const K& key, U&& value) {
     auto it = map_.find(key);
     if (it != map_.end()) {
       vlist_.splice(vlist_.begin(), vlist_, it->second);
       return {it->second, false};
     }
 
-    vlist_.emplace_front(key, std::move(value));
+    vlist_.emplace_front(key, std::forward<U>(value));
     map_[key] = vlist_.begin();
 
     trim();
@@ -77,7 +79,7 @@ class LRUCache {
     return {vlist_.begin(), true};
   }
 
-  list_iter erase(list_iter pos) {
+  iterator erase(iterator pos) {
     map_.erase(pos->first);
     return vlist_.erase(pos);
   }