Summary

Fixes #24140

Variables annotated with Self (from typing or typing_extensions) are now recognized as same-class instances and no longer trigger SLF001 for private member access.

from typing import Self

class Foo:
    def __init__(self, x: int) -> None:
        self._x = x

    def foo(self) -> None:
        this: Self = self
        print(this._x)  # previously SLF001, now OK

Changes

Added Self type check in SameClassInstanceChecker::match_annotation using semantic.match_typing_expr(annotation, "Self")
Added test fixture SLF001_self.py covering: Self annotation on variable, Self annotation on parameter, Self in classmethod, and cross-class access (still flagged)

Test Plan

this: Self = self accessing this._private -> no diagnostic
other: Self as parameter accessing other._private -> no diagnostic
other: DifferentClass accessing other._private -> SLF001 still flagged