Add a const constructor

src/lib.rs

@@ -78,20 +78,25 @@ struct Entry<T> {
 
 impl<T, const N: usize> Default for LRUCache<T, N> {
     fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T, const N: usize> LRUCache<T, N> {
+    /// Create an empty cache.
+    pub const fn new() -> Self {
         let cache = LRUCache {
-            entries: ArrayVec::new(),
+            entries: ArrayVec::new_const(),
             head: 0,
             tail: 0,
         };
         assert!(
-            cache.entries.capacity() < u16::max_value() as usize,
+            N < u16::max_value() as usize,
             "Capacity overflow"
         );
         cache
     }
-}
 
-impl<T, const N: usize> LRUCache<T, N> {
     /// Insert a given key in the cache.
     ///
     /// This item becomes the front (most-recently-used) item in the cache.  If the cache is full,

src/tests.rs

@@ -20,7 +20,7 @@ where
 
 #[test]
 fn empty() {
-    let mut cache = TestCache::default();
+    let mut cache = TestCache::new();
     assert_eq!(cache.is_empty(), true);
     assert_eq!(items(&mut cache), []);
     cache.insert(1);