diff --git a/crates/ty_python_semantic/resources/mdtest/intersection_types.md b/crates/ty_python_semantic/resources/mdtest/intersection_types.md index 022e09c43b..c2637b2afd 100644 --- a/crates/ty_python_semantic/resources/mdtest/intersection_types.md +++ b/crates/ty_python_semantic/resources/mdtest/intersection_types.md @@ -907,6 +907,11 @@ def unknown( Dynamic types do not cancel each other out. Intersecting an unknown set of values with the negation of another unknown set of values is not necessarily empty, so we keep the positive contribution: +```toml +[environment] +python-version = "3.12" +``` + ```py from typing import Any from ty_extensions import Intersection, Not, Unknown @@ -924,6 +929,50 @@ def unknown( ) -> None: reveal_type(i1) # revealed: Unknown reveal_type(i2) # revealed: Unknown + +class Covariant[T]: + def get(self) -> T: + raise NotImplementedError + +def covariant( + i1: Intersection[Covariant[Any], Not[Covariant[Any]]], + i2: Intersection[Not[Covariant[Any]], Covariant[Any]], +) -> None: + reveal_type(i1) # revealed: Covariant[Any] + reveal_type(i2) # revealed: Covariant[Any] + +class Contravariant[T]: + def receive(self, input: T): ... + +def contravariant( + i1: Intersection[Contravariant[Any], Not[Contravariant[Any]]], + i2: Intersection[Not[Contravariant[Any]], Contravariant[Any]], +) -> None: + reveal_type(i1) # revealed: Contravariant[Any] + reveal_type(i2) # revealed: Contravariant[Any] + +class Invariant[T]: + mutable_attribute: T + +def invariant( + i1: Intersection[Invariant[Any], Not[Invariant[Any]]], + i2: Intersection[Not[Invariant[Any]], Invariant[Any]], +) -> None: + reveal_type(i1) # revealed: Invariant[Any] + reveal_type(i2) # revealed: Invariant[Any] + +class Bivariant[T]: ... + +# Because of bivariance, the specialisation here is meaningless; +# `Bivariant[Any]` is arguably still a fully static type, even +# though it is specialised with a gradual form! Thus self-cancellation +# here is fine: +def bivariant( + i1: Intersection[Bivariant[Any], Not[Bivariant[Any]]], + i2: Intersection[Not[Bivariant[Any]], Bivariant[Any]], +) -> None: + reveal_type(i1) # revealed: Never + reveal_type(i2) # revealed: Never ``` ### Mixed dynamic types diff --git a/crates/ty_python_semantic/src/types/builder.rs b/crates/ty_python_semantic/src/types/builder.rs index c279ddbd27..5536de4295 100644 --- a/crates/ty_python_semantic/src/types/builder.rs +++ b/crates/ty_python_semantic/src/types/builder.rs @@ -1048,6 +1048,12 @@ impl<'db> InnerIntersectionBuilder<'db> { self.positive.insert(Type::Never); return; } + // `T & ~T` = `T` if `T` is not a subtype of `T` + // (this can only be true if `T` is a non-fully-static type) + if existing_negative.is_equivalent_to(db, new_positive) { + to_remove.push(index); + continue; + } // A & ~B = A if A and B are disjoint if existing_negative.is_disjoint_from(db, new_positive) { to_remove.push(index); @@ -1136,6 +1142,11 @@ impl<'db> InnerIntersectionBuilder<'db> { self.positive.insert(Type::Never); return; } + // `T & ~T` = `T` if `T` is not a subtype of `T` + // (this can only be true if `T` is a non-fully-static type) + if existing_positive.is_equivalent_to(db, new_negative) { + return; + } // A & ~B = A if A and B are disjoint if existing_positive.is_disjoint_from(db, new_negative) { return;