Incorrect type on Source->timestamp

[moseslecce]

The PHPDoc type for the field $timestamp is set as int in Smarty\Template\Source, however there are many examples that exist which set the timestamp to false in the event that there is no source file found.

Here are some notable examples:

src/Resource/StringEval

public function populate(\Smarty\Template\Source $source, \Smarty\Template $_template = null)
 {
    $source->uid = sha1($source->name);
    $source->timestamp = $source->exists = true;
 }

src/Resource/StreamPlugin

public function populate(Source $source, ?Template $_template = null) {
    $source->uid = false;
    $source->content = $this->getContent($source);
    $source->timestamp = $source->exists = !!$source->content;
}

src/Resource/FilePlugin

public function populate(Source $source, ?Template $_template = null) {
    $source->uid = sha1(
        $source->name . ($source->isConfig ? $source->getSmarty()->_joined_config_dir :
        $source->getSmarty()->_joined_template_dir)
     );

    if ($path = $this->getFilePath($source->name, $source->getSmarty(), $source->isConfig)) {
         if (isset($source->getSmarty()->security_policy) && is_object($source->getSmarty()->security_policy)) {
            $source->getSmarty()->security_policy->isTrustedResourceDir($path, $source->isConfig);
        }
        $source->exists = true;
        $source->timestamp = filemtime($path);
    } else {
        $source->timestamp = $source->exists = false;
    }
}

If this is intended, the type should likely be changed to int|false.