Merge pull request #223 from mobusoperandi/insert_move

feat: return type does not have to be Clone

README.md

@@ -128,12 +128,10 @@ The following apply to the key type and to the function's return type:
 - [`'static`]: key and return values are owned by a store which is owned by a static.
 - [`Send`] and [`Sync`]: for parallel access.
 
-And the return type must be [`Clone`] because it is cloned for insertion into the store.
-
 ## Store bounds
 
 Another source of bounds on the key type and the return type is the implementation of [`MemoizationStore`] for the store type.
-By the way, the provided implementation of [`MemoizationStore`] for the default store type [`HashMap`] bounds `K: Eq + Hash`.
+By the way, the provided implementation of [`MemoizationStore`] for the default store type [`HashMap`] bounds `K: Eq + Hash, R: Clone`.
 
 # Generic functions
 

macro/src/lib.rs

@@ -146,7 +146,7 @@ fn expand_fn_block(original_fn_block: Block, return_type: Type, attr_args: AttrA
         // However, since the concrete store is already obtained and since presumably the
         // following `::get` should be cheap, releasing the exclusive lock, obtaining a read lock
         // and obtaining the store again does not seem reasonable.
-        let attempt: ::core::option::Option<#return_type> = ::michie::MemoizationStore::get(store, #key_ref).cloned();
+        let attempt: ::core::option::Option<#return_type> = ::michie::MemoizationStore::get(store, #key_ref);
         ::core::mem::drop(type_map_mutex_guard);
         if let ::core::option::Option::Some(hit) = attempt {
             hit
@@ -170,8 +170,7 @@ fn expand_fn_block(original_fn_block: Block, return_type: Type, attr_args: AttrA
                 }
                 downcast_mut_with_inference_hint::<#store_type>(store, || #store_init).unwrap()
             };
-            ::michie::MemoizationStore::insert(store, #key, ::core::clone::Clone::clone(&miss));
-            miss
+            ::michie::MemoizationStore::insert(store, #key, miss)
         }
     }}
 }

src/lib.rs

@@ -9,30 +9,34 @@ use std::{
 pub use michie_macro::memoized;
 
 pub trait MemoizationStore<K, R> {
-    fn insert(&mut self, key: K, value: R);
-    fn get(&self, key: &K) -> Option<&R>;
+    fn insert(&mut self, key: K, value: R) -> R;
+    fn get(&self, key: &K) -> Option<R>;
 }
 
 impl<K, R> MemoizationStore<K, R> for HashMap<K, R>
 where
     K: Eq + Hash,
+    R: Clone,
 {
-    fn insert(&mut self, key: K, value: R) {
-        HashMap::insert(self, key, value);
+    fn insert(&mut self, key: K, value: R) -> R {
+        HashMap::insert(self, key, value.clone());
+        value
     }
-    fn get(&self, key: &K) -> Option<&R> {
-        HashMap::get(self, key)
+    fn get(&self, key: &K) -> Option<R> {
+        HashMap::get(self, key).cloned()
     }
 }
 
 impl<K, R> MemoizationStore<K, R> for BTreeMap<K, R>
 where
     K: Ord,
+    R: Clone,
 {
-    fn insert(&mut self, key: K, value: R) {
-        BTreeMap::insert(self, key, value);
+    fn insert(&mut self, key: K, value: R) -> R {
+        BTreeMap::insert(self, key, value.clone());
+        value
     }
-    fn get(&self, key: &K) -> Option<&R> {
-        BTreeMap::get(self, key)
+    fn get(&self, key: &K) -> Option<R> {
+        BTreeMap::get(self, key).cloned()
     }
 }

tests/compile_fail/store_init_omitted_and_default_not_implemented.rs

@@ -2,8 +2,10 @@ use michie::{memoized, MemoizationStore};
 
 struct Store;
 impl MemoizationStore<usize, usize> for Store {
-    fn insert(&mut self, _key: usize, _value: usize) {}
-    fn get(&self, _key: &usize) -> Option<&usize> {
+    fn insert(&mut self, _key: usize, value: usize) -> usize {
+        value
+    }
+    fn get(&self, _key: &usize) -> Option<usize> {
         None
     }
 }

tests/compile_fail/store_init_omitted_and_default_not_implemented.stderr

@@ -1,7 +1,7 @@
 error[E0277]: the trait bound `Store: Default` is not satisfied
-  --> tests/compile_fail/store_init_omitted_and_default_not_implemented.rs:10:1
+  --> tests/compile_fail/store_init_omitted_and_default_not_implemented.rs:12:1
    |
-10 | #[memoized(key_expr = input, store_type = Store)]
+12 | #[memoized(key_expr = input, store_type = Store)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Default` is not implemented for `Store`
    |
    = note: this error originates in the attribute macro `memoized` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/test.rs

@@ -83,8 +83,10 @@ fn store_init_is_omitted() {
         }
     }
     impl MemoizationStore<usize, usize> for Store {
-        fn insert(&mut self, _key: usize, _value: usize) {}
-        fn get(&self, _key: &usize) -> Option<&usize> {
+        fn insert(&mut self, _key: usize, value: usize) -> usize {
+            value
+        }
+        fn get(&self, _key: &usize) -> Option<usize> {
             None
         }
     }
@@ -110,8 +112,10 @@ fn store_init_is_used_instead_of_implementation_of_the_default_trait() {
         }
     }
     impl MemoizationStore<usize, usize> for Store {
-        fn insert(&mut self, _key: usize, _value: usize) {}
-        fn get(&self, _key: &usize) -> Option<&usize> {
+        fn insert(&mut self, _key: usize, value: usize) -> usize {
+            value
+        }
+        fn get(&self, _key: &usize) -> Option<usize> {
             None
         }
     }
@@ -142,8 +146,10 @@ fn store_init_includes_a_concrete_store_type() {
         }
     }
     impl<K, R> MemoizationStore<K, R> for Store<K, R> {
-        fn insert(&mut self, _key: K, _value: R) {}
-        fn get(&self, _key: &K) -> Option<&R> {
+        fn insert(&mut self, _key: K, value: R) -> R {
+            value
+        }
+        fn get(&self, _key: &K) -> Option<R> {
             None
         }
     }
@@ -165,8 +171,10 @@ fn store_init_includes_function_from_impl_block_that_has_bound_on_k_and_v() {
         }
     }
     impl MemoizationStore<usize, usize> for Store<()> {
-        fn insert(&mut self, _key: usize, _value: usize) {}
-        fn get(&self, _key: &usize) -> Option<&usize> {
+        fn insert(&mut self, _key: usize, value: usize) -> usize {
+            value
+        }
+        fn get(&self, _key: &usize) -> Option<usize> {
             None
         }
     }
@@ -193,7 +201,7 @@ fn trait_functions_are_called_explicitly() {
     }
     impl MemoizationStore<(), ()> for Store {
         fn insert(&mut self, _key: (), _value: ()) {}
-        fn get(&self, _key: &()) -> Option<&()> {
+        fn get(&self, _key: &()) -> Option<()> {
             None
         }
     }