typing/conformance/tests/generics_self_advanced.py at d159fd32b9c6217fee3aaa149f68647c96f2bf9c · python/typing · GitHub

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"""
Tests for advanced or special-case usage of the typing.Self type.
"""

from typing import assert_type, Self


class ParentA:
    # Test for property that returns Self.
    @property
    def prop1(self) -> Self:
        raise NotImplementedError

class ChildA(ParentA):
    ...


assert_type(ParentA().prop1, ParentA)
assert_type(ChildA().prop1, ChildA)


# Test for a child that accesses an attribute within a parent
# whose type is annotated using Self.
class ParentB:
    a: list[Self]

    @classmethod
    def method1(cls) -> Self:
        raise NotImplementedError

class ChildB(ParentB):
    b: int = 0

    def method2(self) -> None:
        assert_type(self, Self)
        assert_type(self.a, list[Self])
        assert_type(self.a[0], Self)
        assert_type(self.method1(), Self)

    @classmethod
    def method3(cls) -> None:
        assert_type(cls, type[Self])
        cls.a # E: Access to generic instance variables via class is ambiguous
        assert_type(cls.method1(), Self)

ChildB.a # E: Ambigous access
ParentB.a = [ChildB.method1()] # E: Ambigous write