Merge 531ca7e47a into d755f3b522

crates/ty_python_semantic/resources/mdtest/assignment/annotations.md

@@ -542,8 +542,7 @@ e: list[Any] | None = [1]
 reveal_type(e)  # revealed: list[Any]
 
 f: list[Any] | None = f2(1)
-# TODO: Better constraint solver.
+reveal_type(f)  # revealed: list[Any] | None
-reveal_type(f)  # revealed: list[int] | None
 
 g: list[Any] | dict[Any, Any] = f3(1)
 # TODO: Better constraint solver.
@@ -600,6 +599,48 @@ reveal_type(x7)  # revealed: Contravariant[Any]
 reveal_type(x8)  # revealed: Invariant[Any]
 ```
 
+## Declared type preference sees through subtyping
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+from typing import Any, Iterable, Literal, MutableSequence, Sequence
+
+x1: Sequence[Any] = [1, 2, 3]
+reveal_type(x1)  # revealed: list[Any]
+
+x2: MutableSequence[Any] = [1, 2, 3]
+reveal_type(x2)  # revealed: list[Any]
+
+x3: Iterable[Any] = [1, 2, 3]
+reveal_type(x3)  # revealed: list[Any]
+
+class X[T]:
+    value: T
+
+    def __init__(self, value: T): ...
+
+class A[T](X[T]): ...
+
+def a[T](value: T) -> A[T]:
+    return A(value)
+
+x4: A[object] = A(1)
+reveal_type(x4)  # revealed: A[object]
+
+x5: X[object] = A(1)
+reveal_type(x5)  # revealed: A[object]
+
+x6: X[object] | None = A(1)
+reveal_type(x6)  # revealed: A[object]
+
+x7: X[object] | None = a(1)
+reveal_type(x7)  # revealed: A[object]
+```
+
 ## Narrow generic unions
 
 ```toml

crates/ty_python_semantic/resources/mdtest/literal_promotion.md

@@ -341,3 +341,58 @@ reveal_type(x21)  # revealed: X[Literal[1]]
 x22: X[Literal[1]] | None = x(1)
 reveal_type(x22)  # revealed: X[Literal[1]]
 ```
+
+## Literal annotations see through subtyping
+
+```py
+from typing import Any, Iterable, Literal, MutableSequence, Sequence
+
+x1: Sequence[Literal[1, 2, 3]] = [1, 2, 3]
+reveal_type(x1)  # revealed: list[Literal[1, 2, 3]]
+
+x2: MutableSequence[Literal[1, 2, 3]] = [1, 2, 3]
+reveal_type(x2)  # revealed: list[Literal[1, 2, 3]]
+
+x3: Iterable[Literal[1, 2, 3]] = [1, 2, 3]
+reveal_type(x3)  # revealed: list[Literal[1, 2, 3]]
+
+class Sup1[T]:
+    value: T
+
+class Sub1[T](Sup1[T]): ...
+
+def sub1[T](value: T) -> Sub1[T]:
+    return Sub1()
+
+x4: Sub1[Literal[1]] = sub1(1)
+reveal_type(x4)  # revealed: Sub1[Literal[1]]
+
+x5: Sup1[Literal[1]] = sub1(1)
+reveal_type(x5)  # revealed: Sub1[Literal[1]]
+
+x6: Sup1[Literal[1]] | None = sub1(1)
+reveal_type(x6)  # revealed: Sub1[Literal[1]]
+
+x7: Sup1[Literal[1]] | None = sub1(1)
+reveal_type(x7)  # revealed: Sub1[Literal[1]]
+
+class Sup2A[T, U]:
+    value: tuple[T, U]
+
+class Sup2B[T, U]:
+    value: tuple[T, U]
+
+class Sub2[T, U](Sup2A[T, Any], Sup2B[Any, U]): ...
+
+def sub2[T, U](x: T, y: U) -> Sub2[T, U]:
+    return Sub2()
+
+x8 = sub2(1, 2)
+reveal_type(x8)  # revealed: Sub2[int, int]
+
+x9: Sup2A[Literal[1], Literal[2]] = sub2(1, 2)
+reveal_type(x9)  # revealed: Sub2[Literal[1], int]
+
+x10: Sup2B[Literal[1], Literal[2]] = sub2(1, 2)
+reveal_type(x10)  # revealed: Sub2[int, Literal[2]]
+```

crates/ty_python_semantic/resources/mdtest/type_compendium/tuple.md

@@ -57,6 +57,9 @@ reveal_type(tuple((1, 2)))  # revealed: tuple[Literal[1], Literal[2]]
 
 reveal_type(tuple([1]))  # revealed: tuple[Unknown | int, ...]
 
+x1: tuple[int, ...] = tuple([1])
+reveal_type(x1)  # revealed: tuple[int, ...]
+
 # error: [invalid-argument-type]
 reveal_type(tuple[int]([1]))  # revealed: tuple[int]
 

crates/ty_python_semantic/src/types.rs

@@ -1083,7 +1083,10 @@ impl<'db> Type<'db> {
     }
 
     /// If this type is a class instance, returns its specialization.
-    pub(crate) fn class_specialization(self, db: &'db dyn Db) -> Option<Specialization<'db>> {
+    pub(crate) fn class_specialization(
+        self,
+        db: &'db dyn Db,
+    ) -> Option<(ClassLiteral<'db>, Specialization<'db>)> {
         self.specialization_of_optional(db, None)
     }
 
@@ -1094,15 +1097,17 @@ impl<'db> Type<'db> {
         expected_class: ClassLiteral<'_>,
     ) -> Option<Specialization<'db>> {
         self.specialization_of_optional(db, Some(expected_class))
+            .map(|(_, specialization)| specialization)
     }
 
     fn specialization_of_optional(
         self,
         db: &'db dyn Db,
         expected_class: Option<ClassLiteral<'_>>,
-    ) -> Option<Specialization<'db>> {
+    ) -> Option<(ClassLiteral<'db>, Specialization<'db>)> {
         let class_type = match self {
             Type::NominalInstance(instance) => instance,
+            Type::ProtocolInstance(instance) => instance.to_nominal_instance()?,
             Type::TypeAlias(alias) => alias.value_type(db).as_nominal_instance()?,
             _ => return None,
         }
@@ -1113,7 +1118,49 @@ impl<'db> Type<'db> {
             return None;
         }
 
-        specialization
+        Some((class_literal, specialization?))
+    }
+
+    /// Given a type variable `T` from the generic context of a class `C`:
+    /// - If `self` is a specialized instance of `C`, returns the type assigned to `T` on `self`.
+    /// - If `self` is a specialized instance of some class `A[T]`, and `C[T]` is a subclass of
+    ///   `A[T]`, returns the type assigned to `T` on `self`.
+    pub(crate) fn find_type_var_from(
+        self,
+        db: &'db dyn Db,
+        bound_typevar: BoundTypeVarInstance<'db>,
+        class: ClassLiteral<'db>,
+    ) -> Option<Type<'db>> {
+        if let Some(specialization) = self.specialization_of(db, class) {
+            return specialization.get(db, bound_typevar);
+        }
+
+        // TODO: We should use the constraint solver here to determine the type mappings for more
+        // complex subtyping relationships, e.g., callables, protocols, or unions containing multiple
+        // generic elements.
+        for base in class.iter_mro(db, None).skip(1) {
+            let Some((base, Some(base_specialization))) =
+                base.into_class().map(|class| class.class_literal(db))
+            else {
+                continue;
+            };
+
+            if let Some(specialization) = self.specialization_of(db, base) {
+                for (base_typevar, base_ty) in base_specialization
+                    .generic_context(db)
+                    .variables(db)
+                    .zip(base_specialization.types(db))
+                {
+                    if *base_ty == Type::TypeVar(bound_typevar) {
+                        return specialization.get(db, base_typevar);
+                    }
+                }
+
+                return None;
+            }
+        }
+
+        None
     }
 
     /// Returns the top materialization (or upper bound materialization) of this type, which is the
@@ -4035,23 +4082,26 @@ impl<'db> Type<'db> {
             return;
         };
 
-        let tcx_specialization = tcx.annotation.and_then(|tcx| {
+        for (type_var, ty) in specialization
-            tcx.filter_union(db, |ty| ty.specialization_of(db, class_literal).is_some())
-                .specialization_of(db, class_literal)
-        });
-
-        for (typevar, ty) in specialization
             .generic_context(db)
             .variables(db)
             .zip(specialization.types(db))
         {
-            let variance = typevar.variance_with_polarity(db, polarity);
+            let variance = type_var.variance_with_polarity(db, polarity);
-            let tcx = TypeContext::new(tcx_specialization.and_then(|spec| spec.get(db, typevar)));
+            let narrowed_tcx = tcx.and_then(|annotation| match annotation {
+                Type::Union(union) => union
+                    .elements(db)
+                    .iter()
+                    .filter_map(|ty| ty.find_type_var_from(db, type_var, class_literal))
+                    .exactly_one()
+                    .ok(),
+                _ => annotation.find_type_var_from(db, type_var, class_literal),
+            });
 
-            f(typevar, *ty, variance, tcx);
+            f(type_var, *ty, variance, narrowed_tcx);
 
             visitor.visit(*ty, || {
-                ty.visit_specialization_impl(db, tcx, variance, f, visitor);
+                ty.visit_specialization_impl(db, narrowed_tcx, variance, f, visitor);
             });
         }
     }
@@ -6249,30 +6299,35 @@ impl<'db> Type<'db> {
                 }
 
                 Some(KnownClass::Tuple) => {
-                    let object = Type::object();
+                    let element_ty =
+                        BoundTypeVarInstance::synthetic(db, "T", TypeVarVariance::Covariant);
 
                     // ```py
-                    // class tuple:
+                    // class tuple(Sequence[_T_co]):
                     //     @overload
                     //     def __new__(cls) -> tuple[()]: ...
                     //     @overload
-                    //     def __new__(cls, iterable: Iterable[object]) -> tuple[object, ...]: ...
+                    //     def __new__(cls, iterable: Iterable[_T_co]) -> tuple[_T_co, ...]: ...
                     // ```
                     CallableBinding::from_overloads(
                         self,
                         [
                             Signature::new(Parameters::empty(), Some(Type::empty_tuple(db))),
-                            Signature::new(
+                            Signature::new_generic(
+                                Some(GenericContext::from_typevar_instances(db, [element_ty])),
                                 Parameters::new(
                                     db,
                                     [Parameter::positional_only(Some(Name::new_static(
                                         "iterable",
                                     )))
                                     .with_annotated_type(
-                                        KnownClass::Iterable.to_specialized_instance(db, [object]),
+                                        KnownClass::Iterable.to_specialized_instance(
+                                            db,
+                                            [Type::TypeVar(element_ty)],
+                                        ),
                                     )],
                                 ),
-                                Some(Type::homogeneous_tuple(db, object)),
+                                Some(Type::homogeneous_tuple(db, Type::TypeVar(element_ty))),
                             ),
                         ],
                     )

crates/ty_python_semantic/src/types/bound_super.rs

@@ -321,7 +321,7 @@ impl<'db> BoundSuperType<'db> {
             Type::NominalInstance(instance) => SuperOwnerKind::Instance(instance),
 
             Type::ProtocolInstance(protocol) => {
-                if let Some(nominal_instance) = protocol.as_nominal_type() {
+                if let Some(nominal_instance) = protocol.to_nominal_instance() {
                     SuperOwnerKind::Instance(nominal_instance)
                 } else {
                     return Err(BoundSuperError::AbstractOwnerType {

crates/ty_python_semantic/src/types/call/bind.rs

@@ -3001,10 +3001,40 @@ impl<'a, 'db> ArgumentTypeChecker<'a, 'db> {
 
         // Prefer the declared type of generic classes.
         let preferred_type_mappings = return_with_tcx.and_then(|(return_ty, tcx)| {
-            tcx.filter_union(self.db, |ty| ty.class_specialization(self.db).is_some())
+            let (tcx_class, tcx_specialization) = tcx
+                .filter_union(self.db, |ty| ty.class_specialization(self.db).is_some())
                 .class_specialization(self.db)?;
 
-            builder.infer(return_ty, tcx).ok()?;
+            let Some((return_class, return_specialization)) = return_ty
+                .filter_union(self.db, |ty| ty.class_specialization(self.db).is_some())
+                .class_specialization(self.db)
+            else {
+                builder.infer(return_ty, tcx).ok()?;
+                return Some(builder.type_mappings().clone());
+            };
+
+            // TODO: We should use the constraint solver here to determine the type mappings for more
+            // complex subtyping relationships, e.g., callables, protocols, or unions containing multiple
+            // generic elements.
+            for base in return_class.iter_mro(self.db, Some(return_specialization)) {
+                let Some((base_class, Some(base_specialization))) =
+                    base.into_class().map(|class| class.class_literal(self.db))
+                else {
+                    continue;
+                };
+
+                if base_class == tcx_class {
+                    for (base_ty, tcx_ty) in std::iter::zip(
+                        base_specialization.types(self.db),
+                        tcx_specialization.types(self.db),
+                    ) {
+                        builder.infer(*base_ty, *tcx_ty).ok()?;
+                    }
+
+                    break;
+                }
+            }
+
             Some(builder.type_mappings().clone())
         });
 

crates/ty_python_semantic/src/types/infer.rs

@@ -381,6 +381,12 @@ impl<'db> TypeContext<'db> {
         }
     }
 
+    pub(crate) fn and_then(self, f: impl FnOnce(Type<'db>) -> Option<Type<'db>>) -> Self {
+        Self {
+            annotation: self.annotation.and_then(f),
+        }
+    }
+
     pub(crate) fn is_typealias(&self) -> bool {
         self.annotation
             .is_some_and(|ty| ty.is_typealias_special_form())

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

@@ -7832,41 +7832,24 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             annotation.filter_disjoint_elements(self.db(), collection_ty, inferable)
         });
 
-        // Extract the annotated type of `T`, if provided.
-        let annotated_elt_tys = tcx
-            .known_specialization(self.db(), collection_class)
-            .map(|specialization| specialization.types(self.db()));
-
         // Create a set of constraints to infer a precise type for `T`.
         let mut builder = SpecializationBuilder::new(self.db(), inferable);
 
-        match annotated_elt_tys {
+        for elt_ty in elt_tys.clone() {
-            // The annotated type acts as a constraint for `T`.
+            let elt_tcx = tcx
-            //
+                .annotation
-            // Note that we infer the annotated type _before_ the elements, to more closely match the
+                // The annotated type acts as a constraint for `T`.
-            // order of any unions as written in the type annotation.
+                //
-            Some(annotated_elt_tys) => {
+                // Note that we infer the annotated type _before_ the elements, to more closely match the
-                for (elt_ty, annotated_elt_ty) in iter::zip(elt_tys.clone(), annotated_elt_tys) {
+                // order of any unions as written in the type annotation.
-                    builder
+                .and_then(|tcx| tcx.find_type_var_from(self.db(), elt_ty, class_literal))
-                        .infer(Type::TypeVar(elt_ty), *annotated_elt_ty)
+                // If a valid type annotation was not provided, avoid restricting the type of the collection
-                        .ok()?;
+                // by unioning the inferred type with `Unknown`.
-                }
+                .unwrap_or(Type::unknown());
-            }
 
-            // If a valid type annotation was not provided, avoid restricting the type of the collection
+            builder.infer(Type::TypeVar(elt_ty), elt_tcx).ok()?;
-            // by unioning the inferred type with `Unknown`.
-            None => {
-                for elt_ty in elt_tys.clone() {
-                    builder.infer(Type::TypeVar(elt_ty), Type::unknown()).ok()?;
-                }
-            }
         }
 
-        let elt_tcxs = match annotated_elt_tys {
-            None => Either::Left(iter::repeat(TypeContext::default())),
-            Some(tys) => Either::Right(tys.iter().map(|ty| TypeContext::new(Some(*ty)))),
-        };
-
         for elts in elts {
             // An unpacking expression for a dictionary.
             if let &[None, Some(value)] = elts.as_slice() {
@@ -7889,10 +7872,11 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             }
 
             // The inferred type of each element acts as an additional constraint on `T`.
-            for (elt, elt_ty, elt_tcx) in itertools::izip!(elts, elt_tys.clone(), elt_tcxs.clone())
+            for (elt, elt_ty) in iter::zip(elts, elt_tys.clone()) {
-            {
                 let Some(elt) = elt else { continue };
 
+                let elt_tcx =
+                    tcx.and_then(|tcx| tcx.find_type_var_from(self.db(), elt_ty, class_literal));
                 let inferred_elt_ty = infer_elt_expression(self, elt, elt_tcx);
 
                 // Simplify the inference based on the declared type of the element.
@@ -8392,7 +8376,6 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
         call_expression: &ast::ExprCall,
         tcx: TypeContext<'db>,
     ) -> Type<'db> {
-        // TODO: Use the type context for more precise inference.
         let callable_type =
             self.infer_maybe_standalone_expression(&call_expression.func, TypeContext::default());
 

crates/ty_python_semantic/src/types/instance.rs

@@ -165,7 +165,7 @@ impl<'db> Type<'db> {
         // This matches the behaviour of other type checkers, and is required for us to
         // recognise `str` as a subtype of `Container[str]`.
         structurally_satisfied.or(db, || {
-            let Some(nominal_instance) = protocol.as_nominal_type() else {
+            let Some(nominal_instance) = protocol.to_nominal_instance() else {
                 return ConstraintSet::from(false);
             };
 
@@ -175,7 +175,7 @@ impl<'db> Type<'db> {
             // `Q`'s members in a Liskov-incompatible way.
             let type_to_test = self
                 .as_protocol_instance()
-                .and_then(ProtocolInstanceType::as_nominal_type)
+                .and_then(ProtocolInstanceType::to_nominal_instance)
                 .map(Type::NominalInstance)
                 .unwrap_or(self);
 
@@ -658,7 +658,7 @@ impl<'db> ProtocolInstanceType<'db> {
     /// If this is a synthesized protocol that does not correspond to a class definition
     /// in source code, return `None`. These are "pure" abstract types, that cannot be
     /// treated in a nominal way.
-    pub(super) fn as_nominal_type(self) -> Option<NominalInstanceType<'db>> {
+    pub(super) fn to_nominal_instance(self) -> Option<NominalInstanceType<'db>> {
         match self.inner {
             Protocol::FromClass(class) => {
                 Some(NominalInstanceType(NominalInstanceInner::NonTuple(*class)))