[ty] Add cycle handling to lazy_default

Author: MichaReiser

Cargo.lock

@@ -146,7 +146,7 @@ regex-automata = { version = "0.4.9" }
 rustc-hash = { version = "2.0.0" }
 rustc-stable-hash = { version = "0.1.2" }
 # When updating salsa, make sure to also update the revision in `fuzz/Cargo.toml`
-salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "ef9f9329be6923acd050c8dddd172e3bc93e8051", default-features = false, features = [
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "8c5d8315b5dc61c3ad7c3df71c7323c3d98f3bd4", default-features = false, features = [
     "compact_str",
     "macros",
     "salsa_unstable",

Cargo.toml

@@ -1,2 +1,2 @@
 spark  # too many iterations (in `exported_names` query), `should not be able to access instance member `spark` of type variable IndexOpsLike@astype in inferable position`
-steam.py  # dependency graph cycle when querying TypeVarInstance < 'db >::lazy_default_(Id(2e007)), set cycle_fn/cycle_initial to fixpoint iterate.
+steam.py  # too many iterations

crates/ty_python_semantic/resources/primer/bad.txt

@@ -8359,7 +8359,7 @@ impl<'db> TypeVarInstance<'db> {
         Some(TypeVarBoundOrConstraints::Constraints(ty))
     }
 
-    #[salsa::tracked(heap_size=ruff_memory_usage::heap_size)]
+    #[salsa::tracked(cycle_fn=lazy_default_cycle_recover, cycle_initial=lazy_default_cycle_initial, heap_size=ruff_memory_usage::heap_size)]
     fn lazy_default(self, db: &'db dyn Db) -> Option<Type<'db>> {
         let definition = self.definition(db)?;
         let module = parsed_module(db, definition.file(db)).load(db);
@@ -8401,6 +8401,23 @@ fn lazy_bound_cycle_initial<'db>(
     None
 }
 
+#[allow(clippy::ref_option)]
+fn lazy_default_cycle_recover<'db>(
+    _db: &'db dyn Db,
+    _value: &Option<Type<'db>>,
+    _count: u32,
+    _self: TypeVarInstance<'db>,
+) -> salsa::CycleRecoveryAction<Option<Type<'db>>> {
+    salsa::CycleRecoveryAction::Iterate
+}
+
+fn lazy_default_cycle_initial<'db>(
+    _db: &'db dyn Db,
+    _self: TypeVarInstance<'db>,
+) -> Option<Type<'db>> {
+    None
+}
+
 /// Where a type variable is bound and usable.
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, salsa::Update, get_size2::GetSize)]
 pub enum BindingContext<'db> {

crates/ty_python_semantic/src/types.rs

@@ -30,7 +30,7 @@ ty_python_semantic = { path = "../crates/ty_python_semantic" }
 ty_vendored = { path = "../crates/ty_vendored" }
 
 libfuzzer-sys = { git = "https://github.com/rust-fuzz/libfuzzer", default-features = false }
-salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "ef9f9329be6923acd050c8dddd172e3bc93e8051", default-features = false, features = [
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "8c5d8315b5dc61c3ad7c3df71c7323c3d98f3bd4", default-features = false, features = [
     "compact_str",
     "macros",
     "salsa_unstable",