False positives of UnusedVariable in fn() functions

[ghnp5]

Hello,

Since the last version (or some earlier, but recently), I keep getting false positives of VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable in arrow functions.

Example:

$ignoredDirs = array_map(fn($dir) => PREFIX_DIR.$dir, PHP_ERROR_LOGS['ignore_dirs']);

It says that $dir is unused.

It happens for all arrow functions, seems, and for all parameters of those functions.

Using PHP 8.3, on Windows.

Thanks!

[sirbrillig]

Thanks for the report! The scope for functions is tricky to get right and I definitely could have broken something.

I'm not able to reproduce the issue in my test classes, though. 🤔 I wonder what's causing it. Here's the test case I added. If you put this into your code, does it report a warning?

function arrowFunctionWithConcatOperator() {
	$ignoredDirs = array_map(fn($dir) => PREFIX_DIR.$dir, PHP_ERROR_LOGS['ignore_dirs']);
	return $ignoredDirs;
}

If not, maybe it's interacting with the other code around the line you posted above. Can you come up with a small function like the above that demonstrates the false positive?

[sirbrillig]

Ah wait! I see, I get the false positive if I put that line at the top level of a file.

array_map(
	fn($dir) => PREFIX_DIR.$dir, // false positive warning
	PHP_ERROR_LOGS['ignore_dirs']
);

I probably didn't account for arrow functions outside of a function scope.

[ghnp5]

Thanks! Surprisingly, that doesn't trigger the warning. But if you put the line of code in the global scope (outside any function or class), that will trigger the warning.

EDIT - I see you already figured that part out 😁

[sirbrillig]

Should be fixed in 2.11.22. Thanks for reporting!