Revert "break recursion cycle"

This reverts commit ee68251407.

crates/ty_python_semantic/src/types.rs

@@ -7595,15 +7595,11 @@ impl<'db> Type<'db> {
         tcx: TypeContext<'db>,
         visitor: &ApplyTypeMappingVisitor<'db>,
     ) -> Type<'db> {
+        // If we are binding `typing.Self`, and this type is what we are binding `Self` to, return
+        // early. This is not just an optimization, it also prevents us from infinitely expanding
+        // the type, if it's something that can contain a `Self` reference.
         match type_mapping {
-            // If we are binding `typing.Self`, and this type is what we are binding `Self` to, return
-            // early. This is not just an optimization, it also prevents us from infinitely expanding
-            // the type, if it's something that can contain a `Self` reference.
             TypeMapping::BindSelf { self_type, .. } if self == *self_type => return self,
-
-            // If we are breaking a recursive type, look for that before expanding this type.
-            TypeMapping::BreakRecursionCycle(target) if self == *target => return Type::unknown(),
-
             _ => {}
         }
 
@@ -7622,7 +7618,7 @@ impl<'db> Type<'db> {
                         TypeMapping::BindSelf { .. } |
                         TypeMapping::ReplaceSelf { .. } |
                         TypeMapping::Materialize(_) |
-                        TypeMapping::BreakRecursionCycle(_) |
+                        TypeMapping::ReplaceParameterDefaults |
                         TypeMapping::EagerExpansion => self,
                     }
                 }
@@ -7798,7 +7794,7 @@ impl<'db> Type<'db> {
                 TypeMapping::BindSelf { .. } |
                 TypeMapping::ReplaceSelf { .. } |
                 TypeMapping::Materialize(_) |
-                TypeMapping::BreakRecursionCycle(_) |
+                TypeMapping::ReplaceParameterDefaults |
                 TypeMapping::EagerExpansion |
                 TypeMapping::PromoteLiterals(PromoteLiteralsMode::Off) => self,
                 TypeMapping::PromoteLiterals(PromoteLiteralsMode::On) => self.promote_literals_impl(db, tcx)
@@ -7811,7 +7807,7 @@ impl<'db> Type<'db> {
                 TypeMapping::BindSelf { .. } |
                 TypeMapping::ReplaceSelf { .. } |
                 TypeMapping::PromoteLiterals(_) |
-                TypeMapping::BreakRecursionCycle(_) |
+                TypeMapping::ReplaceParameterDefaults |
                 TypeMapping::EagerExpansion => self,
                 TypeMapping::Materialize(materialization_kind) => match materialization_kind {
                     MaterializationKind::Top => Type::object(),
@@ -8088,12 +8084,11 @@ impl<'db> Type<'db> {
         .find_legacy_typevars(db, None, variables);
     }
 
-    /// Looks for any recursive references to this type inside of itself, replacing them with
-    /// `Unknown`.
-    pub(crate) fn break_recursion_cycle(self, db: &'db dyn Db) -> Type<'db> {
+    /// Replace default types in parameters of callables with `Unknown`.
+    pub(crate) fn replace_parameter_defaults(self, db: &'db dyn Db) -> Type<'db> {
         self.apply_type_mapping(
             db,
-            &TypeMapping::BreakRecursionCycle(self),
+            &TypeMapping::ReplaceParameterDefaults,
             TypeContext::default(),
         )
     }
@@ -8533,9 +8528,9 @@ pub enum TypeMapping<'a, 'db> {
     ReplaceSelf { new_upper_bound: Type<'db> },
     /// Create the top or bottom materialization of a type.
     Materialize(MaterializationKind),
-    /// Looks for any recursive references to a type inside of itself, replacing them with
-    /// `Unknown`.
-    BreakRecursionCycle(Type<'db>),
+    /// Replace default types in parameters of callables with `Unknown`. This is used to avoid infinite
+    /// recursion when the type of the default value of a parameter depends on the callable itself.
+    ReplaceParameterDefaults,
     /// Apply eager expansion to the type.
     /// In the case of recursive type aliases, this will diverge, so that part will be replaced with `Divergent`.
     EagerExpansion,
@@ -8554,7 +8549,7 @@ impl<'db> TypeMapping<'_, 'db> {
             | TypeMapping::PromoteLiterals(_)
             | TypeMapping::BindLegacyTypevars(_)
             | TypeMapping::Materialize(_)
-            | TypeMapping::BreakRecursionCycle(_)
+            | TypeMapping::ReplaceParameterDefaults
             | TypeMapping::EagerExpansion => context,
             TypeMapping::BindSelf {
                 binding_context, ..
@@ -8588,7 +8583,7 @@ impl<'db> TypeMapping<'_, 'db> {
             | TypeMapping::BindLegacyTypevars(_)
             | TypeMapping::BindSelf { .. }
             | TypeMapping::ReplaceSelf { .. }
-            | TypeMapping::BreakRecursionCycle(_)
+            | TypeMapping::ReplaceParameterDefaults
             | TypeMapping::EagerExpansion => self.clone(),
         }
     }
@@ -10185,7 +10180,7 @@ impl<'db> BoundTypeVarInstance<'db> {
                 }
             }
             TypeMapping::PromoteLiterals(_)
-            | TypeMapping::BreakRecursionCycle(_)
+            | TypeMapping::ReplaceParameterDefaults
             | TypeMapping::BindLegacyTypevars(_)
             | TypeMapping::EagerExpansion => Type::TypeVar(self),
             TypeMapping::Materialize(materialization_kind) => {

crates/ty_python_semantic/src/types/infer/builder.rs

@@ -8248,7 +8248,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                     if let Some(default) = param.default() {
                         parameter = parameter.with_default_type(
                             self.infer_expression(default, TypeContext::default())
-                                .break_recursion_cycle(self.db()),
+                                .replace_parameter_defaults(self.db()),
                         );
                     }
                     parameter
@@ -8262,7 +8262,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                     if let Some(default) = param.default() {
                         parameter = parameter.with_default_type(
                             self.infer_expression(default, TypeContext::default())
-                                .break_recursion_cycle(self.db()),
+                                .replace_parameter_defaults(self.db()),
                         );
                     }
                     parameter
@@ -8280,7 +8280,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                     if let Some(default) = param.default() {
                         parameter = parameter.with_default_type(
                             self.infer_expression(default, TypeContext::default())
-                                .break_recursion_cycle(self.db()),
+                                .replace_parameter_defaults(self.db()),
                         );
                     }
                     parameter

crates/ty_python_semantic/src/types/signatures.rs

@@ -544,7 +544,7 @@ impl<'db> Signature<'db> {
                 defaults
                     .next()
                     .expect("should have optional default for each non-variadic parameter")
-                    .map(|ty| ty.break_recursion_cycle(db))
+                    .map(|ty| ty.replace_parameter_defaults(db))
             });
         }
         let mut parameters = Parameters::new(db, inferred_signature.parameters);
@@ -2202,9 +2202,13 @@ impl<'db> ParameterKind<'db> {
         visitor: &ApplyTypeMappingVisitor<'db>,
     ) -> Self {
         let apply_to_default_type = |default_type: &Option<Type<'db>>| {
-            default_type
-                .as_ref()
-                .map(|ty| ty.apply_type_mapping_impl(db, type_mapping, tcx, visitor))
+            if type_mapping == &TypeMapping::ReplaceParameterDefaults && default_type.is_some() {
+                Some(Type::unknown())
+            } else {
+                default_type
+                    .as_ref()
+                    .map(|ty| ty.apply_type_mapping_impl(db, type_mapping, tcx, visitor))
+            }
         };
 
         match self {