title: What does :: mean in Rust?
body: <p>What does the <code>::</code> syntax in Rust, as seen <a href="http://doc.rust-lang.org/0.11.0/src/collections/home/rustbuild/src/rust-buildbot/slave/dist2-linux/build/src/libcollections/trie.rs.html#428-428" rel="noreferrer">here</a>, mean:</p>
  
  <pre><code>fn chunk(n: uint, idx: uint) -&gt; uint {
      let sh = uint::BITS - (SHIFT * (idx + 1));
      (n &gt;&gt; sh) &amp; MASK
  }
  </code></pre>
  
  <p>In languages like Haskell it means a type hint, but here the compiler already has an annotation of that values type, so it seems it's likely type casting.</p>