assert.unknownExpr - Phpstan

Code example

php

<?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:

diff-php

 <?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:

diff-php

 <?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);
     }
 }