Star operator without enclosing within parentheses

[thorwhalen]

Describe the bug

Returning a tuple containing star operator without enclosing with parentheses leads to a Cannot parse error.

Oh no! 💥 💔 💥

To Reproduce

def apply_to_last(input, func):
    *header, last = input
    return *header, func(last)

# which is valid code doing this:
assert apply_to_last([1,2,3], lambda x: x+10) == (1, 2, 13)

And try to blackify...

Expected behavior

I expect it to not choke.

There is a workaround -- enclosing in parentheses

def apply_to_last(input, func):
    *header, last = input
    return (*header, func(last))

But doing this makes the linter complain that "Remove redundant parentheses".

Environment (please complete the following information):

• Version: axblack 20210720
• MacOS 10.15.7
• Python 3.8.6

[JelleZijlstra]

What python version do you have in your settings? This code is invalid in 3.6.

[thorwhalen]

As in python --version right?

I ask because I mentioned it above:

3.8.6

[JelleZijlstra]

No, I mean Black's target-version setting. By default Black assumes your code is 3.6-compatible. Does it work if you limit your target-version to 3.8+.

We could perhaps autodetect this grammar change though and detect that the code is 3.8+.