Values parsed as constant arguments are not destructed

[AjaniBilby]

Values are not destructed when parsed to a constant argument.

Example:

class Person{ name: int; }

fn println(val: #Person) {
  println(val.name);
}

int main() {
  let p = Blank#[Person]();
  println($p); // the clone was never destructed

  delete p;
}