Prevent accidental object copies

[Nycto]

I've got an object where I would like the compiler to fail if I accidentally 
try to copy an instance of it. Overloading proc = seems to be the way to do 
this, but I'm struggling to get the exact incantation to also allow for 
instantiation. Here is my starting point:
    
    
    type Person = object
      first, last: string
    
    proc newPerson(first, last: string): Person =
      result.first = first
      result.last = last
    
    proc `=`*[T](d: var Person; src: Person) {.error.} =
      discard
    
    let person = newPerson("John", "Doe")
    echo person.first, " ", person.last
    
    

This blows up on let person = because, as you might have guessed, that calls =.

What is the approach I should take here? And thanks for any help you can offer.