E_INVALID_EXPRESSION: Invalid expression <undefined>

I am using expressJS with edge template engine for views. I have tried something like this but don’t know why it is showing 'Invalid expression passed to @set

 @set ('i', '[Number(current) > 5 ? Number(current) - 4 : 1]') 

Tried to reproduce it from ejs logic but it is not working. Any help will be much appreciated.