Add Global Function to Volt Compiler

Hi,

I'm trying to implement that converting all strings to function.

$compiler->addFunction('*', function ($resolvedArgs, $exprArgs){
    return 'call_user_func(' . $resolvedArgs . ')';
});

My helper:

function foo {}
function bar {}
function theme_url {}

For example usage on volt:

{{ foo('hello') }}

{{ bar('world') }}

{{ theme_url('path') }}

I tried with * sign but didnt work

Phalcon\Mvc\View\Exception: Macro 'theme_url' does not exist