Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/subscript/instance.md

@@ -0,0 +1,44 @@
+# Instance subscript
+
+## Getitem unbound
+
+```py
+class NotSubscriptable: ...
+
+a = NotSubscriptable()[0]  # error: "Cannot subscript object of type `NotSubscriptable` with no `__getitem__` method"
+```
+
+## Getitem not callable
+
+```py
+class NotSubscriptable:
+    __getitem__ = None
+
+# error: "Method `__getitem__` of type `Unknown | None` is not callable on object of type `NotSubscriptable`"
+a = NotSubscriptable()[0]
+```
+
+## Valid getitem
+
+```py
+class Identity:
+    def __getitem__(self, index: int) -> int:
+        return index
+
+reveal_type(Identity()[0])  # revealed: int
+```
+
+## Getitem union
+
+```py
+def _(flag: bool):
+    class Identity:
+        if flag:
+            def __getitem__(self, index: int) -> int:
+                return index
+        else:
+            def __getitem__(self, index: int) -> str:
+                return str(index)
+
+    reveal_type(Identity()[0])  # revealed: int | str
+```