title: Rust adding associated type with u32
body: <p>I have an associated type <code>MyType</code>.</p>
  <p>This type is going to be an unsigned integer, but I use it because the size of the unsigned integer required for this variable is maybe going to change in the future. So <code>MyType</code> is going to be one of: <code>u32</code>, <code>u64</code>, <code>u128</code>.</p>
  <p>So MyType will look like this when defined: <code>MyType = u32</code> (of course it may not be <code>u32</code>).</p>
  <p>In my code, I need to increment this variable of type <code>MyType</code> by one.</p>
  <p>so I have to do this: <code>let n: MyType = v + 1</code>, where v is the type of <code>MyType</code>.</p>
  <p>How can I do this, what trait restrictions should <code>MyType</code> have?</p>
  <p>I would want something like this: <code>type MyType: UnsignedInt</code>, but the problem is there is no number trait in rust as far as I have seen.</p>