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[red-knot] Understand typing.Tuple (#14927)
Co-authored-by: Alex Waygood <[email protected]>
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‎crates/red_knot_python_semantic/resources/mdtest/subscript/tuple.md‎

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@@ -72,3 +72,55 @@ def _(m: int, n: int):
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# TODO: Support overloads... Should be `tuple[Literal[1, 'a', b"b"] | None, ...]`
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reveal_type(tuple_slice) # revealed: @Todo(return type)
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```
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## Inheritance
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```toml
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[environment]
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target-version = "3.9"
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```
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```py
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# TODO:
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# * `tuple.__class_getitem__` is always bound on 3.9 (`sys.version_info`)
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# * `tuple[int, str]` is a valid base (generics)
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# error: [call-possibly-unbound-method] "Method `__class_getitem__` of type `Literal[tuple]` is possibly unbound"
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# error: [invalid-base] "Invalid class base with type `GenericAlias` (all bases must be a class, `Any`, `Unknown` or `Todo`)"
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class A(tuple[int, str]): ...
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# Runtime value: `(A, tuple, object)`
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# TODO: Generics
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reveal_type(A.__mro__) # revealed: tuple[Literal[A], Unknown, Literal[object]]
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```
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## `typing.Tuple`
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### Correspondence with `tuple`
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`typing.Tuple` can be used interchangeably with `tuple`:
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```py
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from typing import Tuple
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class A: ...
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def _(c: Tuple, d: Tuple[int, A], e: Tuple[Any, ...]):
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reveal_type(c) # revealed: tuple
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reveal_type(d) # revealed: tuple[int, A]
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reveal_type(e) # revealed: @Todo(full tuple[...] support)
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```
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### Inheritance
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Inheriting from `Tuple` results in a MRO with `builtins.tuple` and `typing.Generic`. `Tuple` itself
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is not a class.
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```py
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from typing import Tuple
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class C(Tuple): ...
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# Runtime value: `(C, tuple, typing.Generic, object)`
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# TODO: Add `Generic` to the MRO
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reveal_type(C.__mro__) # revealed: tuple[Literal[C], Literal[tuple], Unknown, Literal[object]]
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```

‎crates/red_knot_python_semantic/src/types.rs‎

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@@ -1758,6 +1758,7 @@ impl<'db> Type<'db> {
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Type::ClassLiteral(_) | Type::SubclassOf(_) => self.to_instance(db),
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// We treat `typing.Type` exactly the same as `builtins.type`:
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Type::KnownInstance(KnownInstanceType::Type) => KnownClass::Type.to_instance(db),
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Type::KnownInstance(KnownInstanceType::Tuple) => KnownClass::Tuple.to_instance(db),
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Type::Union(union) => union.map(db, |element| element.in_type_expression(db)),
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Type::Unknown => Type::Unknown,
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// TODO map this to a new `Type::TypeVar` variant
@@ -2137,6 +2138,8 @@ pub enum KnownInstanceType<'db> {
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Never,
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/// The symbol `typing.Any` (which can also be found as `typing_extensions.Any`)
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Any,
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/// The symbol `typing.Tuple` (which can also be found as `typing_extensions.Tuple`)
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Tuple,
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/// The symbol `typing.Type` (which can also be found as `typing_extensions.Type`)
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Type,
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/// A single instance of `typing.TypeVar`
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Self::NoReturn => "NoReturn",
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Self::Never => "Never",
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Self::Any => "Any",
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Self::Tuple => "Tuple",
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Self::Type => "Type",
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Self::TypeAliasType(_) => "TypeAliasType",
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}
@@ -2173,6 +2177,7 @@ impl<'db> KnownInstanceType<'db> {
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| Self::NoReturn
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| Self::Never
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| Self::Any
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| Self::Tuple
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| Self::Type
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| Self::TypeAliasType(_) => Truthiness::AlwaysTrue,
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}
@@ -2188,6 +2193,7 @@ impl<'db> KnownInstanceType<'db> {
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Self::NoReturn => "typing.NoReturn",
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Self::Never => "typing.Never",
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Self::Any => "typing.Any",
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Self::Tuple => "typing.Tuple",
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Self::Type => "typing.Type",
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Self::TypeVar(typevar) => typevar.name(db),
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Self::TypeAliasType(_) => "typing.TypeAliasType",
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Self::NoReturn => KnownClass::SpecialForm,
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Self::Never => KnownClass::SpecialForm,
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Self::Any => KnownClass::Object,
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Self::Type => KnownClass::Object,
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Self::Tuple => KnownClass::SpecialForm,
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Self::Type => KnownClass::SpecialForm,
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Self::TypeVar(_) => KnownClass::TypeVar,
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Self::TypeAliasType(_) => KnownClass::TypeAliasType,
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}
@@ -2231,6 +2238,7 @@ impl<'db> KnownInstanceType<'db> {
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("typing" | "typing_extensions", "Union") => Some(Self::Union),
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("typing" | "typing_extensions", "NoReturn") => Some(Self::NoReturn),
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("typing" | "typing_extensions", "Never") => Some(Self::Never),
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("typing" | "typing_extensions", "Tuple") => Some(Self::Tuple),
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("typing" | "typing_extensions", "Type") => Some(Self::Type),
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_ => None,
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}

‎crates/red_knot_python_semantic/src/types/infer.rs‎

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@@ -4862,6 +4862,7 @@ impl<'db> TypeInferenceBuilder<'db> {
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Type::Unknown
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}
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KnownInstanceType::Type => self.infer_subclass_of_type_expression(parameters),
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KnownInstanceType::Tuple => self.infer_tuple_type_expression(parameters),
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KnownInstanceType::Any => Type::Any,
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}
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}

‎crates/red_knot_python_semantic/src/types/mro.rs‎

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@@ -364,10 +364,13 @@ impl<'db> ClassBase<'db> {
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| KnownInstanceType::Never
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| KnownInstanceType::Optional => None,
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KnownInstanceType::Any => Some(Self::Any),
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// TODO: classes inheriting from `typing.Type` also have `Generic` in their MRO
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// TODO: Classes inheriting from `typing.Type` et al. also have `Generic` in their MRO
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KnownInstanceType::Type => {
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ClassBase::try_from_ty(db, KnownClass::Type.to_class_literal(db))
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}
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KnownInstanceType::Tuple => {
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ClassBase::try_from_ty(db, KnownClass::Tuple.to_class_literal(db))
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}
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},
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}
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}

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