self-referential NamedTuple leads to spurious "incompatible types" with List[<nothing>]

[carljm]

This code typechecks cleanly:

from typing import List, NamedTuple

class Person(NamedTuple):
    name: str
    age: int
 
people: List[Person] = []

But add a self-referential attribute to the NamedTuple:

from typing import List, NamedTuple

class Person(NamedTuple):
    name: str
    age: int
    kids: List['Person']
 
people: List[Person] = []

And now we get:

namedtuple.py:9: error: Incompatible types in assignment (expression has type List[<nothing>], variable has type List[Person])

If Person is an ordinary class instead of a NamedTuple, the error doesn't appear.

[carljm]

For added fun, if you then do people.append(Person(...)), you get the delightful error message:

namedtuple.py:10: error: Argument 1 to "append" of "list" has incompatible type "Person"; expected "Person"

[ilevkivskyi]

Sorry, this is an old problem. Also there are similar things with other "synthetic types" TypedDict, NewType, aliases etc. that don't work well in the forward-reference context. I was going to work on this, but didn't get to it yet. I will keep this open, since here you provide use-cases that are not mentioned in other issues.

[camio]

I ran into this issue as well, but the error message I received is slightly different.

class Node(NamedTuple):
    children : List['Node']
    
def first_child(n : Node) -> Node:
    return n.children[0]

I get this error:

test.py:10: error: Incompatible return value type (got "test.Node", expected "Node")

[ilevkivskyi]

All examples now work correctly, this is also fixed by #3952. Only an (expected) warning about not fully supported recursive type is emitted.