Version: 2.5.1

$engine = new Engine();
$engine->setStrictTypes();

$engine->renderToString($file);

Result: nothing, because @eval('?>' . $code) mutes Fatal error and php dies without any message.

When @ is manually deleted, php throws error:
PHP Fatal error: strict_types declaration must be the very first statement in the script in /home/martin/Plocha/tools/vendor/latte/latte/src/Latte/Engine.php(161) : eval()'d code on line 2

When setStrictTypes(false); everything is ok

When setTempDirectory(...) with setStrictTypes(true) everything is ok