title: Macro to use import depending on type alias
body: <p>I have a type alias <code>pub type Float = std::f64</code> which I can change to f32 if I want to. </p>
  
  <p>The problem is I need to use PI from either the std::f32 or f64 lib. The way of solving this would be to use a macro which can expand into the correct use declaration.</p>
  
  <p>The first problem I have is that I don't know how to expand <code>Float</code>. </p>
  
  <pre><code>macro_rules! more {
  ($x:tt) =&gt; (stringify!(x));
  }
  </code></pre>
  
  <p>gives me "Float" not "std::f64". is it possible to solve this(and my general problem) in this manner?</p>
  
  <p>Edit:</p>
  
  <p>Essentially my final goal is something like this: </p>
  
  <pre><code>macro_rules! final {
  
  ($x:tt) =&gt; (use_correct_import!(x)); // use std::f32 or use::std::f64 depending on Float
  
  }
  </code></pre>