Did you bring this up on the original issue?
On Mon, Feb 8, 2021 at 10:21 AM Ben Avrahami <[email protected]> wrote:
> In both python 3.7 and 3.8, typing.NamedTuple had some strange behaviour
> regarding multiple inheritance. This behaviour was solved in 3.9
> (bpo-36517), but this fix also barred me from a feature very close to my
> heart: the generic named tuple
>
> ```
> T = TypeVar('T')
> class LLNode(NamedTuple, Generic[T]):
> value: T
> next: Optional[LLNode[T]]
> ```
>
> bpo-36517 was committed because any additional features of other classes
> would be missing from the NamedTuple class at runtime. But Generic has no
> features at runtime, and thus this snippet actually works as expected in
> python 3.7/8. But in 3.9, it raises a TypeError, as bpo-36517 completely
> barred any other bases in a typing.NameTuple subclass.
>
> I propose that instead of wholesale barring multiple inheritance in
> NamedTuple, NamedTuple will allow some pre-defined bases alongside it. It
> will only allow do-nothing mixins with no runtime features (I can only
> think of `Generic` Aliases atm, but perhaps others exist). As before, these
> bases will be actually omitted from the class's bases at runtime.
>
> Any thoughts?
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