Internal Error: Cannot format - on whitespace after backslash

[wvanhed]

Describe the bug

Black generates an INTERNAL ERROR with a file that has a docstring that contains a backslash with a trailing space character. Removing the trailing space solves the issue.

To Reproduce

Create a file file.py with the following content. Note, the 5th but last line (i.e., just above the line with other option) contains a trailing space after the backslash!

def foo():
    """
    Some description
                            ['some option'] 
                            /
                            /    --- ['option b']
    something[here]
                            \    --- ['option c']  (['d', 'e', 'f', 'g'])
                            \ 
                            ['other option']
    """
    pass

And run it with these arguments:

$ black file.py

The resulting error is:

error: cannot format file.py: INTERNAL ERROR: Black produced code that is not equivalent to the source. Please report a bug ....

Expected behavior

No error

Environment

• Black's version: 22.3
• OS and Python version: macos 11.6, python 3.7