title: Show function source code from repl
body: <p>I would like to view the definition of a method in REPL. I follow this link (<a href="https://github.com/JuliaLang/julia/issues/2625" rel="noreferrer">https://github.com/JuliaLang/julia/issues/2625</a>) but it doesn't work:</p>
  
  <pre><code>julia&gt; f(x) = x^2
  f (generic function with 1 method)
  
  julia&gt; expand(f)
  f (generic function with 1 method)
  
  julia&gt; methods(f)
  # 1 method for generic function "f":
  f(x) at REPL[155]:1
  
  julia&gt; implementation(f,1)
  ERROR: UndefVarError: implementation not defined
   in eval_user_input(::Any, ::Base.REPL.REPLBackend) at ./REPL.jl:64
   in macro expansion at ./REPL.jl:95 [inlined]
   in (::Base.REPL.##3#4{Base.REPL.REPLBackend})() at ./event.jl:68
  </code></pre>
  
  <p>It seems that the method <code>implementation</code> doesn't exist.</p>