Describe the Bug

Let's start with the minimal example:

param: Final[str | None] = ""
if param is None:
    raise ValueError()
reveal_type(param)


def foo() -> None:
    reveal_type(param)

The first type is correctly revealed as str but the second inside the function is revealed as str | None. While this would be correct (in my option), if param was not Final, since the variable could change between function definition and function execution, this should not be the case for a Final variable, which explicitly should not change. So given, the Final is respected (which pyrefly should assume), param will never be something else than a str.

(Off-Topic: in this very simple example, one could argue that param should be revealed as a str from the start, as it is initialized as a str and should never change. But that is another topic)

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN0AxVqigAaOpRgA3GCID6TYjAA66YqkqoaiQcKgBtOA0p0APnQByudDAC6dALx1lIF6ohg66zfQhxL1jCIqnShEqh%2BMHQAaiIArjAAopTUlAAUAJSqkjLyijBp3lpZ6KqqmDCeYLi4mXQAtAB8ATbB6GES0rJQCswFRTQlqtW1GSCiIHEM0HAk5IggAMR0AKrTUBBMdGBx6ADG09ZwZViV27w0qAxy6HE02DDp%2BDqsDBkNzUaUbR2SDHGUdpgFwWO4Pb50YD4AC%2BbnQ4xAZEkYCgpEIDFoUAoywACqRkai6GgsHh8HQ9tZIGwAVcINZCKplgBlGBRAAWDAYxDgiAA9LykZVUYReGxeTB0LzMLg9nBeRT0FSaYdJecTKgpBEoKhsLByZSINTNCq6LhiCrZqoyAw2dZ6jJKHA6e0nC4AMyEACMACY4SBoRNUAcIDIhLAKMScAQ5v6gA

(Only applicable for extension issues) IDE Information

No response