Fix dead code and overriden clauses found by the type system

Author: josevalim

lib/ex_doc/formatter/html/templates.ex

@@ -152,10 +152,8 @@ defmodule ExDoc.Formatter.HTML.Templates do
     end)
   end
 
-  defp favicon_path(%{favicon: nil}), do: nil
   defp favicon_path(%{favicon: favicon}), do: "assets/favicon#{Path.extname(favicon)}"
 
-  defp logo_path(%{logo: nil}), do: nil
   defp logo_path(%{logo: logo}), do: "assets/logo#{Path.extname(logo)}"
 
   defp sidebar_type(:exception), do: "modules"

lib/ex_doc/language/elixir.ex

@@ -559,17 +559,17 @@ defmodule ExDoc.Language.Elixir do
 
   defp to_var({:%, meta, [name, _]}, _), do: {:%, meta, [name, {:%{}, meta, []}]}
   defp to_var({:%{}, _, _}, _), do: {:map, [], nil}
+  defp to_var({:<<>>, _, _}, _), do: {:binary, [], nil}
+  defp to_var({:{}, _, _}, _), do: {:tuple, [], nil}
   defp to_var({name, meta, _}, _) when is_atom(name), do: {name, meta, nil}
 
   defp to_var({{:., meta, [_module, name]}, _, _args}, _) when is_atom(name),
     do: {name, meta, nil}
 
   defp to_var([{:->, _, _} | _], _), do: {:function, [], nil}
-  defp to_var({:<<>>, _, _}, _), do: {:binary, [], nil}
-  defp to_var({:{}, _, _}, _), do: {:tuple, [], nil}
   defp to_var({_, _}, _), do: {:tuple, [], nil}
   defp to_var(integer, _) when is_integer(integer), do: {:integer, [], nil}
-  defp to_var(float, _) when is_integer(float), do: {:float, [], nil}
+  defp to_var(float, _) when is_float(float), do: {:float, [], nil}
   defp to_var(list, _) when is_list(list), do: {:list, [], nil}
   defp to_var(atom, _) when is_atom(atom), do: {:atom, [], nil}
   defp to_var(_, position), do: {:"arg#{position}", [], nil}