is_dataclass always evaluates to false with TypeVars

[peku33]

dataclasses.is_dataclass seems to always evaluate to false for generic types.

Environment data

• Language Server version: 2024.8.1
• OS and version: darwin arm64
• Python version (and distribution if applicable, e.g. Anaconda): 3.11.9
• python.analysis.indexing: true
• python.analysis.typeCheckingMode: strict

Code Snippet

from dataclasses import is_dataclass
from typing import TypeVar

T = TypeVar("T")

def test_fn(type_: type[T]) -> T:
    assert is_dataclass(type_)

    print("this is marked as unreachable")

    raise NotImplementedError()

[erictraut]

Could someone from the pylance team please transfer this to the pyright project, since it's a core type checker issue? Thanks!

[peku33]

It looks like this has been fixed in #8738

[erictraut]

This still needs to be fixed.

[erictraut]

This is addressed in pyright 1.1.380.