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Tests the handling of generic protocols.
"""
# Specification: https://typing.readthedocs.io/en/latest/spec/protocol.html#generic-protocols
from typing import Callable, Generic, Iterator, Protocol, Self, TypeVar, assert_type
S = TypeVar("S")
T = TypeVar("T")
T_co = TypeVar("T_co", covariant=True)
T_contra = TypeVar("T_contra", contravariant=True)
class Iterable(Protocol[T_co]):
def __iter__(self) -> Iterator[T_co]:
...
# > Protocol[T, S, ...] is allowed as a shorthand for Protocol, Generic[T, S, ...].
# In particular, the implicit order of type parameters is dictated by
# the order in which they appear in the `Protocol` subscript.
class Proto1(Iterable[T_co], Protocol[S, T_co]):
def method1(self, x: S) -> S:
...
class Concrete1:
def __iter__(self) -> Iterator[int]:
return (x for x in [1, 2, 3])
def method1(self, x: str) -> str:
return ""
p1: Proto1[str, int] = Concrete1() # OK
p2: Proto1[int, str] = Concrete1() # E: incompatible type
# > It is an error to combine the shorthand with Generic[T, S, ...]
class Proto2(Protocol[T_co], Generic[T_co]): # E
...
# > User-defined generic protocols support explicitly declared variance.
class Box(Protocol[T_co]):
def content(self) -> T_co:
...
def func1(box_int: Box[int], box_float: Box[float]):
v1: Box[float] = box_int # OK
v2: Box[int] = box_float # E
class Sender(Protocol[T_contra]):
def send(self, data: T_contra) -> int:
return 0
def func2(sender_int: Sender[int], sender_float: Sender[float]):
v1: Sender[int] = sender_float # OK
v2: Sender[float] = sender_int # E
class AttrProto(Protocol[T]):
attr: T
def func3(attr_int: AttrProto[int], attr_float: AttrProto[float]):
v1: AttrProto[float] = attr_int # E
v2: AttrProto[int] = attr_float # E
# Specification: https://typing.readthedocs.io/en/latest/spec/protocol.html#self-types-in-protocols
# > The self-types in protocols follow the rules for other methods.
# Specification: https://typing.readthedocs.io/en/latest/spec/annotations.html#annotating-instance-and-class-methods
# > In addition, the first argument in an instance method can be annotated
# > with a type variable. In this case the return type may use the same
# > type variable, thus making that method a generic function.
T_bounded = TypeVar("T_bounded", bound="HasParent")
class HasParent(Protocol):
def get_parent(self: T_bounded) -> T_bounded:
...
GenericHasParent = TypeVar("GenericHasParent", bound=HasParent)
def generic_get_parent(n: GenericHasParent) -> GenericHasParent:
return n.get_parent()
class ConcreteHasParent:
def get_parent(self) -> Self:
return self
parent = generic_get_parent(ConcreteHasParent()) # OK
assert_type(parent, ConcreteHasParent)
# Specification: https://typing.readthedocs.io/en/latest/spec/generics.html#use-in-protocols
# > `Self` is valid within Protocols, similar to its use in classes:
class HasParentProperty(Protocol):
@property
def parent(self) -> Self:
...
class ConcreteParentProperty:
@property
def parent(self) -> Self:
return self
class InvalidParentProperty:
@property
def parent(self) -> HasParentProperty:
return ConcreteParentProperty()
hp1: HasParentProperty = ConcreteParentProperty() # OK
hp2: HasParentProperty = InvalidParentProperty() # E
class HasMethod(Protocol):
def m(self, item: T, callback: Callable[[T], str]) -> str:
...
class ConcreteHasMethod:
def m(self, item: T, callback: Callable[[T], str]) -> str:
return ""
class InvalidHasMethod:
def m(self, item: int, callback: Callable[[int], str]) -> str:
return ""
hm1: HasMethod = ConcreteHasMethod() # OK
hm2: HasMethod = InvalidHasMethod() # E
# Specification: https://typing.readthedocs.io/en/latest/spec/generics.html#use-in-protocols
# > Checking a class for assignability to a protocol: If a protocol uses `Self`
# > in methods or attribute annotations, then a class `Foo` is assignable
# > to the protocol if its corresponding methods and attribute annotations use
# > either `Self` or `Foo` or any of `Foo`'s subclasses.
class HasGreaterThan(Protocol):
def __gt__(self, other: Self) -> bool:
...
class ConcreteGreaterThan1:
def __gt__(self, other: Self) -> bool:
return False
class ConcreteGreaterThan2:
def __gt__(self, other: "ConcreteGreaterThan2") -> bool:
return False
class InvalidGreaterThan:
def __gt__(self, other: int) -> bool:
return False
hg1: HasGreaterThan = ConcreteGreaterThan1() # OK
hg2: HasGreaterThan = ConcreteGreaterThan2() # OK
hg3: HasGreaterThan = InvalidGreaterThan() # E
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