psalm.xml

<?xml version="1.0"?>
<psalm
    totallyTyped="true"
    resolveFromConfigFile="true"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="https://getpsalm.org/schema/config"
    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
>
    <projectFiles>
        <directory name="src" />
        <directory name="static-analysis" />
        <ignoreFiles>
            <directory name="vendor" />
            <directory name="src/PHPUnit" />
        </ignoreFiles>
    </projectFiles>

    <issueHandlers>
        <MixedAssignment errorLevel="info" />

        <ImpureStaticProperty>
            <!-- self::$... usages in Enum are used to populate an internal cache, and cause no side-effects -->
            <errorLevel type="suppress">
                <file name="src/Enum.php"/>
            </errorLevel>
        </ImpureStaticProperty>

        <ImpureVariable>
            <!-- $this usages in Enum point themselves to an immutable instance -->
            <errorLevel type="suppress">
                <file name="src/Enum.php"/>
            </errorLevel>
        </ImpureVariable>
    </issueHandlers>
</psalm>