docs: key type is not Clone and related improvements

closes #147

Co-authored-by: José Manuel Peña <josemanuelp2@gmail.com>
Co-authored-by: Pranav Kesavarapu <pranavkesavarapu@gmail.com>

README.md

@@ -98,9 +98,10 @@ The following apply to the key type and to the function's return type:
 
 - [`Sized`]: for one, the instrumentation stores the key in a `let` binding.
 - [`'static`]: key and return values are owned by a store which is owned by a static.
-- [`Clone`]: the key and return values are cloned for insertion into the store.
 - [`Send`] and [`Sync`]: for parallel access.
 
+And the return type must be [`Clone`] because it is cloned for insertion into the store.
+
 ## Store bounds
 
 Bounds on `K` and `R` in the `store_type`'s implementation of [`MemoizationStore`] apply to the key type and the return type respectively.
@@ -116,8 +117,11 @@ use std::hash::Hash;
 #[memoized(key_expr = input.clone())]
 fn f<A, B>(input: A) -> B
 where
-    A: 'static + Clone + Send + Sync + Eq + Hash,
-    B: 'static + Clone + Send + Sync + From<A>,
+    A: 'static + Send + Sync // bounds from instrumentation
+        + Eq + Hash // store-specific bounds
+        + Clone, // used in this function's `key_expr`
+    B: 'static + Send + Sync + Clone // bounds from instrumentation
+        + From<A>, // used in this function's body
 {
     input.into()
 }

tests/test.rs

@@ -33,6 +33,18 @@ fn on_a_generic_fn_in_an_impl_block() {
     assert_eq!(concrete_struct.f("foo"), (false, "foo"));
 }
 
+#[test]
+fn key_type_does_not_need_to_be_clone() {
+    #[memoized(key_expr = input)]
+    fn f<A, B>(input: A) -> B
+    where
+        A: 'static + Copy + Send + Sync + Eq + Hash,
+        B: 'static + Clone + Send + Sync + From<A>,
+    {
+        input.into()
+    }
+}
+
 #[test]
 fn on_a_fn_in_a_trait_impl_block() {
     #[derive(Debug, Clone, Hash, PartialEq, Eq)]