Error type checking nested namedtuples #15061

Bug Report

from typing import NamedTuple

class RaggedFeature(NamedTuple):
  class RowSplits(NamedTuple):
    x: int

  splits: RowSplits

produces an error message of,

Invalid statement in NamedTuple definition; expected "field_name: field_type [= default]"
Expected Behavior

No error. I ran into this writing stubs for real code from here that does use nested namedtuples at runtime. It also type checks fine in pyright. Minor though as type: ignore seems to work fine for it in typeshed.

Your Environment

Latest mypy version 1.2. Default flags/configuration is enough.