title: Terraform error: does not have attribute 'private_ip' for variable
body: <p>Using Terraform version 0.11.7 the code below I get this error:</p>
  
  <pre><code>    * output.aws_runner_private_ip_addresses: Resource 'aws_spot_instance_request.runner' does not have attribute 'private_ip' for variable 'aws_spot_instance_request.runner.*.private_ip'
      * output.aws_walker_private_ip_addresses: Resource 'aws_spot_instance_request.walker' does not have attribute 'private_ip' for variable 'aws_spot_instance_request.walker.*.private_ip
  </code></pre>
  
  <p>The output syntax looks correct according the documentation from <a href="https://www.terraform.io/docs/configuration/outputs.html" rel="nofollow noreferrer">Terraform</a></p>
  
  <p>And terraform spot instance request does have the attribute of private_ip which is stated in Terraform documentation <a href="https://www.terraform.io/docs/providers/aws/r/spot_instance_request.html" rel="nofollow noreferrer">here</a>.</p>
  
  <pre><code>resource "aws_spot_instance_request" "walker" {
    count = 2
    instance_type = "t2.micro"
    ami = "ami-0922553b7b0369273"
    spot_price = "1"
  }
  
  resource "aws_spot_instance_request" "runner" {
    count = 2
    instance_type = "t2.micro"
    ami = "ami-0922553b7b0369273"
    spot_price = "1"
  
  }
  
  output "aws_walker_private_ip_addresses" {
      value = ["${aws_spot_instance_request.walker.*.private_ip}"]
  }
  
  output "aws_runner_private_ip_addresses" {
      value = ["${aws_spot_instance_request.runner.*.private_ip}"]
  }
  </code></pre>
  
  <p>However, if I remove the square brackets from the code, it works and there is no error, but the Terraform document seems to be saying I need to use the square brackets since the value would be a list type of returning list of private_ip addresses for each instance. What am I doing wrong here or misunderstanding?</p>
  
  <p>This works, but seems to contradict the document:</p>
  
  <pre><code>output "aws_walker_private_ip_addresses" {
      value = "${aws_spot_instance_request.walker.*.private_ip}"
  }
  
  output "aws_runner_private_ip_addresses" {
      value = "${aws_spot_instance_request.runner.*.private_ip}"
  }
  </code></pre>