Error Identifier: callable.inVoidCast

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

$fn = function (): int {
    return 42;
};

(void) $fn();

Why is it reported? #

The (void) cast (PHP 8.5+) is used to explicitly discard a return value of a callable that does not require its return value to be used. The (void) cast is intended only for callables marked with #[NoDiscard] where the return value must normally be used. Using (void) on a callable that already allows discarding its return value is unnecessary and misleading.

How to fix it #

Remove the (void) cast since the callable already allows discarding the return value:

 <?php declare(strict_types = 1);
 
 $fn = function (): int {
     return 42;
 };

-(void) $fn();
+$fn();

Or, if the callable’s return value should not be discarded, add the #[NoDiscard] attribute to the callable:

 <?php declare(strict_types = 1);
 
+#[\NoDiscard]
 function compute(): int {
     return 42;
 }

 // Now (void) is meaningful - it explicitly discards a must-use return value
 (void) compute();

How to ignore this error #

You can use the identifier callable.inVoidCast to ignore this error using a comment:

// @phpstan-ignore callable.inVoidCast
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: callable.inVoidCast

Rules that report this error #

PHPStan\Rules\Functions\CallToFunctionStatementWithNoDiscardRule [1]

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