Strange behavior with dataclass InitVar

Wondering what is going on here for the cases 3-6. Running it with --strict, mypy version is 0.761.

import dataclasses
from dataclasses import dataclass, InitVar
from functools import partial

dataclass_alias = dataclass
dataclass_partial = partial(dataclass, frozen=True)
dataclass_decorator = dataclass(frozen=True)

# 1. ok
@dataclass(frozen=True)
class X1:
    value: InitVar[bool] = None


# 2. ok
@dataclasses.dataclass(frozen=True)
class X2:
    default: InitVar[bool] = None


# 3. error: Incompatible types in assignment (expression has type "None", variable has type "InitVar[bool]")
@dataclass_alias(frozen=True)
class X3:
    default: InitVar[bool] = None


# 4. error: Incompatible types in assignment (expression has type "None", variable has type "InitVar[bool]")
@dataclass_partial
class X4:
    default: InitVar[bool] = None

# 5a. error: Too many arguments for "object"
# 5b. error: Incompatible types in assignment (expression has type "None", variable has type "InitVar[bool]")
@dataclass_partial()
class X5:
    default: InitVar[bool] = None


# 6. error: Incompatible types in assignment (expression has type "None", variable has type "InitVar[bool]")
@dataclass_decorator
class X6:
    default: InitVar[bool] = None

Commencez par reproduire les cas fournis avec mypy 0.761 et comparez la manière dont chaque forme de décorateur dataclass est analysée. Suivez la gestion de InitVar et des alias ou partiels de décorateur ; le travail est terminé lorsque les cas ont un résultat documenté et cohérent, ainsi que des diagnostics ou des tests appropriés.