Type not narrowed in walrus assignment inside match

[bersbersbers]

Bug Report

The type of var is not narrowed in match statements including a walrus assignment, such as

match (var := fun()):
    case type():
        ...

To Reproduce

def get_int_or_float() -> int | float:
    return int()

def print_int(i: int) -> None:
    print(i)

# mypy works correctly:
first_int_or_float = get_int_or_float()
match first_int_or_float:
    case int():
        # this use is correct; mypy is correct
        print_int(first_int_or_float)
    case float():
        # this use is incorrect; mypy is correct
        print_int(first_int_or_float)

# mypy fails:
match (second_int_or_float := get_int_or_float()):
    # mypy incorrectly does not narrow type of second_int_or_float
    case int():
        print_int(second_int_or_float)
    case float():
        print_int(second_int_or_float)

https://mypy-play.net/?mypy=master&python=3.10&gist=1a1347df9d076755e9dd6a947c97839a

Expected Behavior

main.py:15: error: Argument 1 to "print_int" has incompatible type "float"; expected "int"  [arg-type]
main.py:23: error: Argument 1 to "print_int" has incompatible type "float"; expected "int"  [arg-type]
Found 2 errors in 1 file (checked 1 source file)

Actual Behavior

main.py:15: error: Argument 1 to "print_int" has incompatible type "float"; expected "int"  [arg-type]
main.py:21: error: Argument 1 to "print_int" has incompatible type "Union[int, float]"; expected "int"  [arg-type]
main.py:23: error: Argument 1 to "print_int" has incompatible type "Union[int, float]"; expected "int"  [arg-type]
main.py:23: error: Name "second_int_or_float" is used before definition  [used-before-def]
Found 4 errors in 1 file (checked 1 source file)

Your Environment

mypy master on Python 3.10, see Playground

[AlexWaygood]

This is already fixed on mypy master; it was fixed by #14844. The fix will be included as part of the next mypy release, mypy 1.2.

Your Environment

mypy master on Python 3.10, see Playground

Note that the "mypy master" option on mypy playground is often several weeks behind the latest commit on mypy's actual master branch. (Mypy playground is a third-party project not developed by the mypy team.)