paramOut.tooWideBool

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;
 }