title: How to declare a const String in stable Rust?
body: <p>I am trying to declare a <code>const String</code> in stable Rust but it does not let me declare it:</p>
  
  <pre><code>const CONSTANT_VALUE: String = String::from("constant value");
  
  fn main() {
      println!("{}", TARGET_PORT_KEY);     
  }
  </code></pre>
  
  <p>It is saying that:</p>
  
  <blockquote>
    <p>Calls in constants are limited to tuple structs and tuple variants</p>
  </blockquote>
  
  <p>I do not want to declare my <code>string</code> as literal and call <code>to_string()</code> on literal all the time. </p>
  
  <p>What is the correct way to declare a constant <code>String</code> value?</p>
  
  <p><a href="https://play.rust-lang.org/?version=stable&amp;mode=debug&amp;edition=2018&amp;gist=a5d41c2cac4b5a2ebdf4ef74617baefa" rel="noreferrer">Playground</a></p>