overload operator `+=` for private member

[mimonot]

Thank you. This works well if the "m" is the right type. But what if the 
private “m” is of a different type and needs conversion?
    
    
    type
      Obj = object
        m: cint
    
    proc `m`*(o: var Obj): var int = int(o.m)  # Error
    
    Run