99fa850e53
## Summary Allow (instances of) subclasses of `Any` and `Unknown` to be assignable to (instances of) other classes, unless they are final. This allows us to get rid of ~1000 false positives, mostly when mock-objects like `unittest.mock.MagicMock` are assigned to various targets. ## Test Plan Adapted and new Markdown tests.
2.1 KiB
Any
Annotation
typing.Any is a way to name the Any type.
from typing import Any
x: Any = 1
x = "foo"
def f():
reveal_type(x) # revealed: Any
Aliased to a different name
If you alias typing.Any to another name, we still recognize that as a spelling of the Any type.
from typing import Any as RenamedAny
x: RenamedAny = 1
x = "foo"
def f():
reveal_type(x) # revealed: Any
Shadowed class
If you define your own class named Any, using that in a type expression refers to your class, and
isn't a spelling of the Any type.
class Any: ...
x: Any
def f():
reveal_type(x) # revealed: Any
# This verifies that we're not accidentally seeing typing.Any, since str is assignable
# to that but not to our locally defined class.
y: Any = "not an Any" # error: [invalid-assignment]
Subclass
The spec allows you to define subclasses of Any.
Subclass has an unknown superclass, which might be int. The assignment to x should not be
allowed, even when the unknown superclass is int. The assignment to y should be allowed, since
Subclass might have int as a superclass, and is therefore assignable to int.
from typing import Any
class Subclass(Any): ...
reveal_type(Subclass.__mro__) # revealed: tuple[Literal[Subclass], Any, Literal[object]]
x: Subclass = 1 # error: [invalid-assignment]
y: int = Subclass()
def _(s: Subclass):
reveal_type(s) # revealed: Subclass
Subclass should not be assignable to a final class though, because Subclass could not possibly
be a subclass of FinalClass:
from typing import final
@final
class FinalClass: ...
f: FinalClass = Subclass() # error: [invalid-assignment]
A use case where this comes up is with mocking libraries, where the mock object should be assignable to any type:
from unittest.mock import MagicMock
x: int = MagicMock()
Invalid
Any cannot be parameterized:
from typing import Any
# error: [invalid-type-form] "Type `typing.Any` expected no type parameter"
def f(x: Any[int]):
reveal_type(x) # revealed: Unknown