No error when attempting to use property object as that property's type

• Are you reporting a bug, or opening a feature request? Bug
• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.

from typing import NamedTuple


class C(NamedTuple):
    a: int = 1


print(C.a * 2)

• What is the actual behavior/output?

mypy a.py produces no output.

• What is the behavior/output you expect?

An error at C.a * 2, as it will cause an error at runtime: TypeError: unsupported operand type(s) for *: 'property' and 'int'

• What are the versions of mypy and Python you are using?

python --version: 3.7.2
mypy --version: 0.660+dev.97d7760dca6d95806a97b02992ae88a082898a0e

Do you see the same issue after installing mypy from Git master? Yes

• What are the mypy flags you are using? (For example --strict-optional) None

Commencez par exécuter mypy a.py avec l’exemple indiqué et confirmez qu’il ne produit aucune sortie, tandis que Python lève le TypeError indiqué. Suivez la manière dont mypy traite l’accès à la propriété de NamedTuple et l’expression arithmétique ; le travail est terminé lorsque mypy signale une erreur à l’emplacement de C.a * 2 pour ce cas.