title: Haskell type signature in lambda expression
body: <p>Suppose I have a lambda expression in my program like:</p>
  
  <pre><code>\x -&gt; f $ x + 1
  </code></pre>
  
  <p>and I want to specify for type safety that x must be an Integer. Something like:</p>
  
  <pre><code>-- WARNING: bad code
  \x::Int -&gt; f $ x + 1
  </code></pre>