Hi,

really love ruff, such a great tool! It also inspired me to learn Rust ;)

I found the following bug, which can be reproduced with this MWE:

def no_redef(value):
    if value:

        def fun(x, y):
            return x

    else:

        def fun(x, y):
            return y

    return fun


def redef(value):
    match value:
        case True:

            def fun(x, y):
                return x

        case False:

            def fun(x, y):
                return y

    return fun

Running ruff throws the following error which (IMO) is a bug:

> ruff redef.py --isolated
redef.py:24:17: F811 Redefinition of unused `fun` from line 19
Found 1 error.

Why is this a bug?
In my understanding both the no_redef and redef function have the same behavior. Thus, F811 should behave the same for both functions, which is not the case.

This behavior is consistent with flake8/pyflakes, however, I think this is a bug in their code as well and I opened a ticket there too (PyCQA/pyflakes#771).

Ruff version

> ruff --version
ruff 0.0.261

pyproject.toml

[tool.ruff]
select = ["F"]
target-version = "py38"

Constantin