Fix stale tracked struct values in later iterations (#1068)

* Fix stale tracked struct values in later iterations

* Remove TODO

Author: MichaReiser

src/active_query.rs

@@ -89,6 +89,8 @@ impl ActiveQuery {
         // Mark all tracked structs from the previous iteration as active.
         self.tracked_struct_ids
             .mark_all_active(active_tracked_ids.iter().copied());
+        self.disambiguator_map
+            .seed(active_tracked_ids.iter().map(|(id, _)| id));
     }
 
     pub(super) fn take_cycle_heads(&mut self) -> CycleHeads {

src/function/execute.rs

@@ -172,7 +172,6 @@ where
         // This is different from `opt_old_memo` which might be from a different revision.
         let mut last_provisional_memo_opt: Option<&Memo<'db, C>> = None;
 
-        // TODO: Can we seed those somehow?
         let mut last_stale_tracked_ids: Vec<(Identity, Id)> = Vec::new();
         let mut iteration_count = IterationCount::initial();
 

src/tracked_struct.rs

@@ -461,11 +461,20 @@ impl DisambiguatorMap {
         result
     }
 
-    pub fn clear(&mut self) {
+    pub(crate) fn seed<'a>(&mut self, identities: impl Iterator<Item = &'a Identity>) {
+        for identity in identities {
+            self.disambiguate(IdentityHash {
+                ingredient_index: identity.ingredient_index,
+                hash: identity.hash,
+            });
+        }
+    }
+
+    pub(crate) fn clear(&mut self) {
         self.map.clear()
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub(crate) fn is_empty(&self) -> bool {
         self.map.is_empty()
     }
 }

tests/cycle_tracked.rs

@@ -302,3 +302,36 @@ fn test_cycle_with_fixpoint_structs() {
             "DidDiscard { key: IterationNode(Id(402)) }",
         ]"#]]);
 }
+
+#[salsa::tracked(debug)]
+struct NameWithOffset<'db> {
+    name: String,
+
+    #[tracked]
+    offset: u32,
+}
+
+#[test]
+fn cycle_tracked_struct_with_tracked_field() {
+    #[salsa::tracked(cycle_initial=|_,_| 0)]
+    fn query_a(db: &dyn salsa::Database) -> u32 {
+        let offset = query_b(db);
+
+        let tracked = NameWithOffset::new(db, "test".to_string(), offset);
+
+        tracked.offset(db)
+    }
+
+    #[salsa::tracked]
+    fn query_b(db: &dyn salsa::Database) -> u32 {
+        let base_offset = query_a(db);
+
+        (base_offset + 1).min(5)
+    }
+
+    let db = salsa::DatabaseImpl::default();
+
+    let result = query_a(&db);
+
+    assert_eq!(result, 5);
+}