Weird inference behavior with frozen dataclasses/maybe bug

[rsdenijs]

pyright 1.1.407

In this code, the frozen dataclass shows different inference behavior when providing explicit type hints on the left hand side of the assignment. This has caused me quite some confusion. I don't know if this is a bug or somehow "expected" according to inference rules.

from dataclasses import dataclass
from typing import Literal

Types = Literal['a', 'b', 'c']

@dataclass
class MyClass[T]:
    value: T

@dataclass(frozen=True)
class MyClassFrozen[T]:
    value: T

m1: MyClass[Types] = MyClass(value='a')
reveal_type(m1)            # MyClass[Literal['a', 'b', 'c']]
m2 = MyClass[Types](value='a')
reveal_type(m2)            # MyClass[Literal['a', 'b', 'c']]
f1: MyClassFrozen[Types] = MyClassFrozen(value='a')
reveal_type(f1)            # MyClassFrozen[Literal['a']]    < ----- Odd case
f2 = MyClassFrozen[Types](value='a')
reveal_type(f2)            # MyClassFrozen[Literal['a', 'b', 'c']]

For reference, mypy infers Union[Literal['a'], Literal['b'], Literal['c']] in all cases