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Error Identifier: assert.unknownExpr

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
{
    /**
     * @phpstan-assert string $this->barProp
     */
    public function doBar(mixed $a): bool
    {
        return is_string($a);
    }
}

Why is it reported? #

The @phpstan-assert PHPDoc tag references a property or expression that does not exist on the class. PHPStan cannot verify the assertion because the target expression cannot be resolved. In the example above, $this->barProp does not exist on the class Foo.

How to fix it #

Reference an existing property or parameter in the assert tag:

 <?php declare(strict_types = 1);
 
 class Foo
 {
+    public mixed $barProp;
+
     /**
      * @phpstan-assert string $this->barProp
      */
     public function doBar(mixed $a): bool
     {
         return is_string($a);
     }
 }

Or fix the assert tag to reference the correct expression:

 <?php declare(strict_types = 1);
 
 class Foo
 {
     /**
-     * @phpstan-assert string $this->barProp
+     * @phpstan-assert string $a
      */
     public function doBar(mixed $a): bool
     {
         return is_string($a);
     }
 }

How to ignore this error #

You can use the identifier assert.unknownExpr to ignore this error using a comment:

// @phpstan-ignore assert.unknownExpr
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: assert.unknownExpr

Rules that report this error #

• PHPStan\Rules\PhpDoc\FunctionAssertRule [1]
• PHPStan\Rules\PhpDoc\MethodAssertRule [1]

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