mypy scoping issue?

test.py

import dataclasses
from typing import List, Union


@dataclasses.dataclass()
class RecordType1:
    pass


@dataclasses.dataclass()
class RecordType2:
    pass


def decode(records: List[Union[RecordType1, RecordType2]], x: int) -> None:
    if x == 1:
        record = RecordType1()
        if record:
            records.append(record)
    elif x == 2:
        record = RecordType2()
        if record:
            records.append(record)


def main() -> None:
    records: List[Union[RecordType1, RecordType2]] = []
    for x in {1, 2, 3}:
        decode(records, x)
    print(records)


if __name__ == '__main__':
    main()

'''
$ mypy --strict test.py
test.py:21: error: Incompatible types in assignment (expression has type "RecordType2", variable has type "RecordType1")
Found 1 error in 1 file (checked 1 source file)
'''

test2.py

import dataclasses
from typing import List, Union


@dataclasses.dataclass()
class RecordType1:
    pass


@dataclasses.dataclass()
class RecordType2:
    pass


def decode(records: List[Union[RecordType1, RecordType2]], x: int) -> None:
    if x == 1:
        if record := RecordType1():
            records.append(record)
    elif x == 2:
        if record := RecordType2():
            records.append(record)


def main() -> None:
    records: List[Union[RecordType1, RecordType2]] = []
    for x in {1, 2, 3}:
        decode(records, x)
    print(records)


if __name__ == '__main__':
    main()

'''
test2.py:20: error: Incompatible types in assignment (expression has type "RecordType2", variable has type "RecordType1")
Found 1 error in 1 file (checked 1 source file)
'''

test3.py

import dataclasses
from typing import List, Union


@dataclasses.dataclass()
class RecordType1:
    pass


@dataclasses.dataclass()
class RecordType2:
    pass


def decode(records: List[Union[RecordType1, RecordType2]], x: int) -> None:
    if x == 1:
        if record := RecordType1():
            records.append(record)

    if x == 2:
        if record := RecordType2():
            records.append(record)


def main() -> None:
    records: List[Union[RecordType1, RecordType2]] = []
    for x in {1, 2, 3}:
        decode(records, x)
    print(records)


if __name__ == '__main__':
    main()

'''
test3.py:21: error: Incompatible types in assignment (expression has type "RecordType2", variable has type "RecordType1")
Found 1 error in 1 file (checked 1 source file)
'''

test4.py

import dataclasses
from typing import List, Union


@dataclasses.dataclass()
class RecordType1:
    pass


@dataclasses.dataclass()
class RecordType2:
    pass


def decode(records: List[Union[RecordType1, RecordType2]], x: int) -> None:
    if x == 1:
        if record := RecordType1():
            records.append(record)
            return None

    if x == 2:
        if record := RecordType2():
            records.append(record)
            return None


def main() -> None:
    records: List[Union[RecordType1, RecordType2]] = []
    for x in {1, 2, 3}:
        decode(records, x)
    print(records)


if __name__ == '__main__':
    main()

'''
test4.py:22: error: Incompatible types in assignment (expression has type "RecordType2", variable has type "RecordType1")
Found 1 error in 1 file (checked 1 source file)
'''

test5.py

import dataclasses
from typing import List, Union

from typing_extensions import reveal_type


@dataclasses.dataclass()
class RecordType1:
    pass


@dataclasses.dataclass()
class RecordType2:
    pass


def decode(records: List[Union[RecordType1, RecordType2]], x: int) -> None:
    if x == 1:
        record = RecordType1()
        if record:
            records.append(record)
    elif x == 2:
        reveal_type(record)
        record = RecordType2()
        if record:
            records.append(record)


def main() -> None:
    records: List[Union[RecordType1, RecordType2]] = []
    for x in {1, 2, 3}:
        decode(records, x)
    print(records)


if __name__ == '__main__':
    main()

'''
$ python test5.py
Traceback (most recent call last):
  File "/divesoft-parser/test5.py", line 37, in <module>
    main()
  File "/divesoft-parser/test5.py", line 32, in main
    decode(records, x)
  File "/divesoft-parser/test5.py", line 23, in decode
    reveal_type(record)
UnboundLocalError: local variable 'record' referenced before assignment

$ mypy --strict test5.py
test5.py:23: note: Revealed type is "test.RecordType1"
test5.py:24: error: Incompatible types in assignment (expression has type "RecordType2", variable has type "RecordType1")
Found 1 error in 1 file (checked 1 source file)
'''