Type is not narrowed in else clause following check via type()

[eroller]

Bug Report

Type is not narrowed in else clause following check via type()

To Reproduce

def check_type(a: int | str) -> None:
    if type(a) is int:
        my_int: int = a
    else:
        my_str: str = a # error: Incompatible types in assignment (expression has type "int | str", variable has type "str")  [assignment]

https://mypy-play.net/?mypy=latest&python=3.13&gist=20dd8e7b2f2f3a3795a78360b3627be7

Expected Behavior
Success: no issues found in 1 source file

Actual Behavior
error: Incompatible types in assignment (expression has type "int | str", variable has type "str") [assignment]

Your Environment

• mypy 1.13.0
• python 3.13

[eroller]

a bug (#10457) on the if clause was previously fixed

[JelleZijlstra]

This behavior is correct. a might be an instance of a subtype of int.

[eroller]

Thank you. I guess that is why isinstance should be the preferred way to perform type narrowing. When I used custom classes with the @final decorator then the type is properly narrowed via type() as expected.