Hello, quick problem that I had with dataclasses.

I wanted to indicate that some dataclasses of my module are private (just used as fields of the final dataclass), thus prefixing them with __ . Example:

from dataclasses import dataclass, field
@dataclass
class __C:
    c: int

@dataclass
class D:
    d: __C = field(default_factory=__C)

This throws a mysterious:

NameError: name '_D__C' is not defined

Is this a bug ?