Error Identifier: match.void

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);

class Foo
{
	public function doFoo(): void
	{
	}

	public function doBar(int $i): void
	{
		$a = match ($i) {
			1 => $this->doFoo(),
			2 => $this->doFoo(),
			default => $this->doFoo(),
		};
	}
}

Why is it reported? #

The result of a match expression is being used (assigned to a variable, passed as an argument, etc.), but all arms of the match return void. A void return type means the method does not return a meaningful value, so the result of this match expression is always void and cannot be meaningfully used.

This typically indicates a logic error – either the match arms should call methods that return values, or the match result should not be used.

How to fix it #

If the match is only used for side effects, use it as a standalone statement without assigning the result:

 public function doBar(int $i): void
 {
-	$a = match ($i) {
+	match ($i) {
 		1 => $this->doFoo(),
 		2 => $this->doFoo(),
 		default => $this->doFoo(),
 	};
 }

Alternatively, if a value is needed, call methods that return meaningful values:

-	public function doFoo(): void
+	public function doFoo(): string
 	{
+		return 'result';
 	}

How to ignore this error #

You can use the identifier match.void to ignore this error using a comment:

// @phpstan-ignore match.void
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: match.void

Rules that report this error #

PHPStan\Rules\Comparison\UsageOfVoidMatchExpressionRule [1]

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