bleh, typing is pain.

error_as_expected.py

from typing import Tuple, Dict, List

class M(object):
    def __init__(self, x: int):
        self.id = x


Models = List[M]


def problem() -> None:
    seen = {}  # type: Dict[int,Models]
    for x in [1, 2]:
        result = list_of_other_items(x)
        seen[x] = result[0]  # error: Incompatible types in assignment (expression has type "M", target has type "List[M]")
    return None


def list_of_other_items(i: int) -> Models:
    return [M(2)]

Change the definition of M to:

from django.db import models
class M(models.Model):
    pass

and suddenly no errors appear :(