Generic propagation into dataclasses doesn't seem to work consistently

[bdowning]

Bug Report

mypy doesn't seem to propagate generics into dataclass-generated methods correctly.

To Reproduce

from dataclasses import dataclass
from typing import TypeVar, Generic, Dict, Any

T = TypeVar("T")


class FloatValue:
    pass


@dataclass
class ValueByKey(Generic[T]):
    values: Dict[Any, T]


def foo(v: ValueByKey[FloatValue]):
    reveal_type(v.values)
    reveal_type(ValueByKey[FloatValue].__init__)

Expected Behavior

:; pipenv run mypy /tmp/footest.py
/tmp/footest.py:17: note: Revealed type is 'builtins.dict[Any, footest.FloatValue*]'
/tmp/footest.py:18: note: Revealed type is 'def (self: footest.ValueByKey[footest.FloatValue*], values: builtins.dict[Any, footest.FloatValue*])'

Actual Behavior

:; pipenv run mypy --version      
mypy 0.790
:; pipenv run mypy /tmp/footest.py
/tmp/footest.py:17: note: Revealed type is 'builtins.dict[Any, footest.FloatValue*]'
/tmp/footest.py:18: note: Revealed type is 'def (self: footest.ValueByKey[T`1], values: builtins.dict[Any, T`1])'

Your Environment

• Mypy version used: 0.790
• Mypy command-line flags: see above
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.7.8
• Operating system and version: Arch Linux