Generic NamedTuples and TypedDict

[crusaderky]

mypy 0.730 doesn't work correctly with classes that descend both from NamedTuple or TypedDict and from Generic. dataclasses instead work fine.

from dataclasses import dataclass
from typing import Generic, NamedTuple, TypeVar
from typing_extensions import TypedDict


T = TypeVar("T")

@dataclass
class A(Generic[T]):
    x: T


class B(NamedTuple, Generic[T]):
    x: T


class C(TypedDict, Generic[T]):
    x: T


"foo" + A(x=1).x
"foo" + B(x=1).x
"foo" + C(x=1)["x"]

mypy output:

21: error: Unsupported operand types for + ("str" and "int")
22: error: Unsupported operand types for + ("str" and "T")
22: error: Argument "x" to "B" has incompatible type "int"; expected "T"
23: error: Unsupported operand types for + ("str" and "T")
23: error: Incompatible types (expression has type "int", TypedDict item "x" has type "T")

Expected output:

21: error: Unsupported operand types for + ("str" and "int")
22: error: Unsupported operand types for + ("str" and "int")
23: error: Unsupported operand types for + ("str" and "int")

[ilevkivskyi]

Generic named tuples and typed dicts are not supported, see feature-request issues:

• Generic named tuples: Support generic NamedTuples #685
• Generic typed dicts: Support for generic TypedDict #3863

The bug currently is that these are not flagged as errors, see #6200