ensure len and capacity methods reflect their intentions

src/poolable.rs

@@ -3,15 +3,20 @@ use std::hash::{BuildHasher, Hash};
 
 /// The trait required to be able to use a type in `BytePool`.
 pub trait Poolable {
+    fn len(&self) -> usize;
     fn capacity(&self) -> usize;
     fn alloc(size: usize) -> Self;
 }
 
 impl<T: Default + Clone> Poolable for Vec<T> {
-    fn capacity(&self) -> usize {
+    fn len(&self) -> usize {
         self.len()
     }
 
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
     fn alloc(size: usize) -> Self {
         vec![T::default(); size]
     }
@@ -22,10 +27,14 @@ where
     K: Eq + Hash,
     S: BuildHasher + Default,
 {
-    fn capacity(&self) -> usize {
+    fn len(&self) -> usize {
         self.len()
     }
 
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
     fn alloc(size: usize) -> Self {
         HashMap::with_capacity_and_hasher(size, Default::default())
     }