title: Is is possible to instruct ghci to use a concrete type for a constraint when evaluating the type of an expression?
body: <p>I can use ghci to evaluate the type of <code>fmap</code>:</p>
  <pre><code>Prelude&gt; :t fmap
  fmap :: Functor f =&gt; (a -&gt; b) -&gt; f a -&gt; f b
  </code></pre>
  <p>Is there a way I can instruct ghci to bind <code>f</code> to a particular instance of <code>Functor</code> and print out the resulting type signature. I.e for <code>[]</code> it would print</p>
  <pre><code>(a -&gt; b) -&gt; [a] -&gt; [b]
  </code></pre>
  <p>If not, are there any tricks or roundabout ways to achieve the same? This would be particularly handy for deriving type signatures of more complicated expressions and functors (e.g. <code>(-&gt;) a</code>).</p>