Phpinspectionsea: Inspection warning 'Suspicious Binary Operator' misgiven with spaceship operator

Created on 28 Aug 2018 · 2Comments · Source: kalessil/phpinspectionsea

Description or screenshot:

This section of code is producing a red inspection warning on the return line:

// Ensure that series with specific types are listed before others
usort($allSeries, function ($firstItem, $secondItem) {
    return !array_key_exists('type', $firstItem) <=> !array_key_exists('type', $secondItem);
});

The message when hovering over is:

Operations priority might differ from what you expect: please wrap needed with '(...)'.

When seeing what the suggested completion is, the inspection is named 'Suspicious binary operations' and the corrected form of the return line looks like this:

return (!array_key_exists('type', $firstItem)) <=> !array_key_exists('type', $secondItem);

To me, the original line doesn't contain any strange operator precedence. As far as I understand PHP, both of the 'not' (!) operators are right associative and should bind to their immediate right expression, which are the results of array_key_exists(). The spaceship (<=>) operator should then work on these two expressions, which has the same precedence as identity ===, which when substituted for the spaceship doesn't produce the warning.

Unless there's some flaw in this logic, then this error shouldn't appear.