Method nat_expr_from_value

crates/kernel/src/whnf.rs:1961–1964

(&mut self, n: Nat)

    if ty_head_id.addr != ind_id.addr {
      return Ok(None);
    }

    // Get the first constructor
    let ctor_id = match self.try_get_const(&ind_id)? {
      Some(KConst::Indc { ctors, .. }) if !ctors.is_empty() => ctors[0].clone(),
      _ => return Ok(None),
    };