An unknown solution error on template

[mardiyah]

How's this error to be solved
    
    
    template no = false
    template ok = true
    template foo : bool =
     var i=0
     if i==0 : no   # <--
     else    : ok
    
    if foo :  echo "Yes"
    
    
    Run

when not invoking foo no error ? Please help solve, thanks before