Static analysis result in case of zip(typing.NamedTuple) is different from in case of zip(tuple)

[Kyurenpoto]

Environment data

Pylance v2021.8.0

• Language Server version: 2021.8.0 (Pyright 1.1.159)
• OS and version: Windows 10 (19043.1151)
• Python version (& distribution if applicable, e.g. Anaconda): 3.9.5 (pipenv)

Expected behaviour

No error in following case when use normal tuple:

x = (["1"], ["2"], [3])
y = list(zip(*x))

for a, b, c in zip(*x):
    print(a, b, c) #1 2 3

And Pylance analyzes the type of variables:

Actual behaviour

Error occured:
Tuple size mismatch: expected 3 but received 1 Pylance(reportGeneralTypeIssues) [11, 5]

from typing import NamedTuple

class T(NamedTuple):
    a: list[str]
    b: list[str]
    c: list[int]

x = T(["1"], ["2"], [3])
y = list(zip(*x))

for a, b, c in zip(*x):
    print(a, b, c) #1 2 3

And Pylance analyzes the type of variables:

This is cleary false-positive behavior.

[erictraut]

Thanks for reporting the issue. I've added support for unpacking of objects that derive from a known-length tuple. This includes named tuples. The change will be included in the next release of pylance.

[heejaechang]

fixed in 2021.8.1 release.