title: How do you enable a Rust "crate feature"?
body: <p>I'm trying to use <a href="https://docs.rs/rand/0.7.2/rand/rngs/struct.SmallRng.html" rel="noreferrer"><code>rand::SmallRng</code></a>. The documentation says</p>
  <blockquote>
  <p>This PRNG is <strong>feature-gated</strong>: to use, you must enable the crate feature <code>small_rng</code>.</p>
  </blockquote>
  <p>I've been searching and can't figure out how to enable &quot;crate features&quot;. The phrase isn't even used anywhere in the Rust docs. This is the best I could come up with:</p>
  <pre class="lang-toml prettyprint-override"><code>[features]
  default = [&quot;small_rng&quot;]
  </code></pre>
  <p>But I get:</p>
  <blockquote>
  <p>Feature <code>default</code> includes <code>small_rng</code> which is neither a dependency nor another feature</p>
  </blockquote>
  <p>Are the docs wrong, or is there something I'm missing?</p>