ruff/crates/red_knot_python_semantic/resources/mdtest/subscript/class.md

Class subscript

Class getitem unbound

class NotSubscriptable: pass
a = NotSubscriptable[0]  # error: "Cannot subscript object of type `Literal[NotSubscriptable]` with no `__class_getitem__` method"

Class getitem

class Identity:
    def __class_getitem__(cls, item: int) -> str:
        return item

a = Identity[0]  
reveal_type(a) # revealed: str

Class getitem union

flag = True

class Identity:
    if flag:
        def __class_getitem__(cls, item: int) -> str:
            return item
    else:
        def __class_getitem__(cls, item: int) -> int:
            return item

a = Identity[0]  
reveal_type(a) # revealed: str | int

Class getitem with class union

flag = True

class Identity1:
    def __class_getitem__(cls, item: int) -> str:
        return item

class Identity2:
    def __class_getitem__(cls, item: int) -> int:
        return item

if flag:
    a = Identity1
else:
    a = Identity2

b = a[0]
reveal_type(a) # revealed: Literal[Identity1, Identity2]
reveal_type(b) # revealed: str | int

Class getitem with unbound method union

flag = True

if flag:
    class Identity:
        def __class_getitem__(self, x: int) -> str:
            pass
else:
    class Identity: pass

a = Identity[42] # error: [call-non-callable] "Method `__class_getitem__` of type `Literal[__class_getitem__] | Unbound` is not callable on object of type `Literal[Identity, Identity]`" 
reveal_type(a) # revealed: str | Unknown 

TODO: Class getitem non-class union

flag = True

if flag:
    class Identity:
        def __class_getitem__(self, x: int) -> str:
            pass
else:
    Identity = 1

a = Identity[42] # error: "Cannot subscript object of type `Literal[Identity] | Literal[1]` with no `__getitem__` method"
# TODO: should _probably_ emit `str | Unknown` 
reveal_type(a) # revealed: Unknown