Merge pull request #58 from kleimkuhler/issue-56-remove-eq-bound

[WIP] Removal of Eq bound on `Q::Val`

examples/hello_world/README.md

@@ -44,7 +44,7 @@ need.
 The `HelloWorldDatabase` trait has one supertrait:
 `salsa::Database`. If we were defining more query groups in our
 application, and we wanted to invoke some of those queries from within
-this query group, we might list those query groupes here. You can also
+this query group, we might list those query groups here. You can also
 list any other traits you want, so long as your final database type
 implements them (this lets you add custom state and so forth to your
 database).

src/derived.rs

@@ -53,6 +53,8 @@ where
 {
     fn should_memoize_value(key: &Q::Key) -> bool;
 
+    fn memoized_value_eq(old_value: &Q::Value, new_value: &Q::Value) -> bool;
+
     fn should_track_inputs(key: &Q::Key) -> bool;
 }
 
@@ -60,12 +62,17 @@ pub enum AlwaysMemoizeValue {}
 impl<DB, Q> MemoizationPolicy<DB, Q> for AlwaysMemoizeValue
 where
     Q: QueryFunction<DB>,
+    Q::Value: Eq,
     DB: Database,
 {
     fn should_memoize_value(_key: &Q::Key) -> bool {
         true
     }
 
+    fn memoized_value_eq(old_value: &Q::Value, new_value: &Q::Value) -> bool {
+        old_value == new_value
+    }
+
     fn should_track_inputs(_key: &Q::Key) -> bool {
         true
     }
@@ -81,6 +88,10 @@ where
         false
     }
 
+    fn memoized_value_eq(_old_value: &Q::Value, _new_value: &Q::Value) -> bool {
+        panic!("cannot reach since we never memoize")
+    }
+
     fn should_track_inputs(_key: &Q::Key) -> bool {
         true
     }
@@ -101,6 +112,10 @@ where
         true
     }
 
+    fn memoized_value_eq(_old_value: &Q::Value, _new_value: &Q::Value) -> bool {
+        false
+    }
+
     fn should_track_inputs(_key: &Q::Key) -> bool {
         false
     }
@@ -243,7 +258,7 @@ where
                 match map.insert(key.clone(), QueryState::in_progress(runtime.id())) {
                     Some(QueryState::Memoized(old_memo)) => Some(old_memo),
                     Some(QueryState::InProgress { .. }) => unreachable!(),
-                    None => None
+                    None => None,
                 }
             }
         };
@@ -262,13 +277,7 @@ where
                 let changed_at = memo.changed_at;
 
                 let new_value = StampedValue { value, changed_at };
-                self.overwrite_placeholder(
-                    runtime,
-                    descriptor,
-                    key,
-                    old_memo.unwrap(),
-                    &new_value,
-                );
+                self.overwrite_placeholder(runtime, descriptor, key, old_memo.unwrap(), &new_value);
                 return Ok(new_value);
             }
         }
@@ -299,9 +308,11 @@ where
         // "backdate" its `changed_at` revision to be the same as the
         // old value.
         if let Some(old_memo) = &old_memo {
-            if old_memo.value.as_ref() == Some(&stamped_value.value) {
-                assert!(old_memo.changed_at <= stamped_value.changed_at);
-                stamped_value.changed_at = old_memo.changed_at;
+            if let Some(old_value) = &old_memo.value {
+                if MP::memoized_value_eq(&old_value, &stamped_value.value) {
+                    assert!(old_memo.changed_at <= stamped_value.changed_at);
+                    stamped_value.changed_at = old_memo.changed_at;
+                }
             }
         }
 

src/input.rs

@@ -42,6 +42,7 @@ struct IsConstant(bool);
 impl<DB, Q> InputStorage<DB, Q>
 where
     Q: Query<DB>,
+    Q::Value: Eq,
     DB: Database,
     Q::Value: Default,
 {
@@ -137,6 +138,7 @@ where
 impl<DB, Q> QueryStorageOps<DB, Q> for InputStorage<DB, Q>
 where
     Q: Query<DB>,
+    Q::Value: Eq,
     DB: Database,
     Q::Value: Default,
 {
@@ -197,6 +199,7 @@ where
 impl<DB, Q> InputQueryStorageOps<DB, Q> for InputStorage<DB, Q>
 where
     Q: Query<DB>,
+    Q::Value: Eq,
     DB: Database,
     Q::Value: Default,
 {

src/lib.rs

@@ -56,7 +56,7 @@ pub trait ParallelDatabase: Database + Send {
 
 pub trait Query<DB: Database>: Debug + Default + Sized + 'static {
     type Key: Clone + Debug + Hash + Eq;
-    type Value: Clone + Debug + Hash + Eq;
+    type Value: Clone + Debug;
     type Storage: plumbing::QueryStorageOps<DB, Self> + Send + Sync;
 }