Re-enable fixpoint iteration for variance computation

Author: Veykril

src/tools/rust-analyzer/crates/hir-expand/src/name.rs

@@ -179,9 +179,10 @@ impl Name {
         self.symbol.as_str()
     }
 
+    #[inline]
     pub fn display<'a>(
         &'a self,
-        db: &dyn crate::db::ExpandDatabase,
+        db: &dyn salsa::Database,
         edition: Edition,
     ) -> impl fmt::Display + 'a {
         _ = db;

src/tools/rust-analyzer/crates/hir-ty/src/db.rs

@@ -273,9 +273,8 @@ pub trait HirDatabase: DefDatabase + std::fmt::Debug {
 
     #[salsa::invoke(crate::variance::variances_of)]
     #[salsa::cycle(
-        // cycle_fn = crate::variance::variances_of_cycle_fn,
-        // cycle_initial = crate::variance::variances_of_cycle_initial,
-        cycle_result = crate::variance::variances_of_cycle_initial,
+        cycle_fn = crate::variance::variances_of_cycle_fn,
+        cycle_initial = crate::variance::variances_of_cycle_initial,
     )]
     fn variances_of(&self, def: GenericDefId) -> Option<Arc<[crate::variance::Variance]>>;
 

src/tools/rust-analyzer/crates/hir-ty/src/variance.rs

@@ -54,14 +54,14 @@ pub(crate) fn variances_of(db: &dyn HirDatabase, def: GenericDefId) -> Option<Ar
     variances.is_empty().not().then(|| Arc::from_iter(variances))
 }
 
-// pub(crate) fn variances_of_cycle_fn(
-//     _db: &dyn HirDatabase,
-//     _result: &Option<Arc<[Variance]>>,
-//     _count: u32,
-//     _def: GenericDefId,
-// ) -> salsa::CycleRecoveryAction<Option<Arc<[Variance]>>> {
-//     salsa::CycleRecoveryAction::Iterate
-// }
+pub(crate) fn variances_of_cycle_fn(
+    _db: &dyn HirDatabase,
+    _result: &Option<Arc<[Variance]>>,
+    _count: u32,
+    _def: GenericDefId,
+) -> salsa::CycleRecoveryAction<Option<Arc<[Variance]>>> {
+    salsa::CycleRecoveryAction::Iterate
+}
 
 pub(crate) fn variances_of_cycle_initial(
     db: &dyn HirDatabase,
@@ -965,7 +965,7 @@ struct S3<T>(S<T, T>);
 struct FixedPoint<T, U, V>(&'static FixedPoint<(), T, U>, V);
 "#,
             expect![[r#"
-                FixedPoint[T: bivariant, U: bivariant, V: bivariant]
+                FixedPoint[T: covariant, U: covariant, V: covariant]
             "#]],
         );
     }