Fix clippy findings and related issues

src/maps.rs

@@ -89,7 +89,7 @@ impl<E: Copy, T: Clone> ElementMap<E, T> {
     /// ```
     pub fn map<U: Clone>(&self, f: impl Fn(&T) -> U) -> ElementMap<E, U> {
         ElementMap {
-            data: self.data.iter().map(|v| f(v)).collect(),
+            data: self.data.iter().map(&f).collect(),
             default: f(&self.default),
             to_index: self.to_index,
         }