Match statement with object matching attribute type

[AiroPi]

Describe the bug
It seems that doing a "type checking" with the object UI in pattern matching seems to not work properly.

Code

class Test:
    def __init__(self, a: int | str):
        self.a: int | str = a

test = Test(5)

match test:
    case Test(a = int()):
        print(test.a + 3)
    case Test(a = str()):
        print(test.a + "3")

Expected behavior
By doing a match with Test(a = int()), python will check test is of type Test AND test.a is of type int.
But pyright "only assert" that test if of type Test. It keep the type int | str for test.a.

VS Code extension or command-line
Both, and in unofficial playground:
https://pyright-playground.decorator-factory.su/?gzip=H4sIAJKQEWQC_32NOwrDQAxEe51icLUiwY1xY8gt0i9is8YLjgmWyhw-EobgImQqoTefsooq7lVtIrgedUbObWuWc9K6zlfIhLYZ3lDb-XCFAvZnhhuEyLzKr2hMIxM9xcoC-w4U0XpQcZuHE59KX3t8wt0LLhj4R8an_mW6oeMP_NNLyNYAAAA%3D

[erictraut]

Yes, this is as designed. The type of the expression test is narrowed to type Test, but the type of test.a is not narrowed in this case. Narrowing is applied only to one expression, not both. Not surprisingly, mypy works the same way.

Your options are:

1. Perform a cast.
2. Create a nested match statement:

match test:
    case Test():
        match test.a:
            case int():
                print(test.a + 3)
            case str():
                print(test.a + "3")