Error Identifier: paramOut.tooWideBool

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);

/**
 * @param-out bool $result
 */
function validate(mixed $input, bool &$result): void
{
	$result = true;
}

Why is it reported? #

The @param-out type declares bool for a by-reference parameter, but PHPStan has determined that the parameter is only ever assigned true (or only ever assigned false). The declared output type is wider than necessary because one of the boolean values is never produced.

This indicates that the @param-out annotation is more permissive than what the function actually assigns.

How to fix it #

Narrow the @param-out type to match what the function actually produces:

 <?php declare(strict_types = 1);
 
 /**
- * @param-out bool $result
+ * @param-out true $result
  */
 function validate(mixed $input, bool &$result): void
 {
 	$result = true;
 }

Or if the function should also produce false in some cases, add that code path:

 <?php declare(strict_types = 1);
 
 /**
  * @param-out bool $result
  */
 function validate(mixed $input, bool &$result): void
 {
-	$result = true;
+	$result = $input !== null;
 }

How to ignore this error #

You can use the identifier paramOut.tooWideBool to ignore this error using a comment:

// @phpstan-ignore paramOut.tooWideBool
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: paramOut.tooWideBool

Rules that report this error #

PHPStan\Rules\TooWideTypehints\TooWideArrowFunctionReturnTypehintRule [1]
PHPStan\Rules\TooWideTypehints\TooWideClosureReturnTypehintRule [1]
PHPStan\Rules\TooWideTypehints\TooWideFunctionParameterOutTypeRule [1]
PHPStan\Rules\TooWideTypehints\TooWideFunctionReturnTypehintRule [1]
PHPStan\Rules\TooWideTypehints\TooWideMethodParameterOutTypeRule [1]
PHPStan\Rules\TooWideTypehints\TooWideMethodReturnTypehintRule [1]
PHPStan\Rules\TooWideTypehints\TooWidePropertyTypeRule [1]

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