Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/stubs/class.md

@@ -0,0 +1,47 @@
+# Class definitions in stubs
+
+## Cyclical class definition
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+In type stubs, classes can reference themselves in their base class definitions. For example, in
+`typeshed`, we have `class str(Sequence[str]): ...`.
+
+```pyi
+class Foo[T]: ...
+
+class Bar(Foo[Bar]): ...
+
+reveal_type(Bar)  # revealed: Literal[Bar]
+reveal_type(Bar.__mro__)  # revealed: tuple[Literal[Bar], Literal[Foo[Bar]], Literal[object]]
+```
+
+## Access to attributes declared in stubs
+
+Unlike regular Python modules, stub files often omit the right-hand side in declarations, including
+in class scope. However, from the perspective of the type checker, we have to treat them as bindings
+too. That is, `symbol: type` is the same as `symbol: type = ...`.
+
+One implication of this is that we'll always treat symbols in class scope as safe to be accessed
+from the class object itself. We'll never infer a "pure instance attribute" from a stub.
+
+`b.pyi`:
+
+```pyi
+from typing import ClassVar
+
+class C:
+    class_or_instance_var: int
+```
+
+```py
+from typing import ClassVar, Literal
+
+from b import C
+
+# No error here, since we treat `class_or_instance_var` as bound on the class.
+reveal_type(C.class_or_instance_var)  # revealed: int
+```