Use :binary instead of String in Macro.to_string for bitstrings

No need for grapheme handling and `str` is never of zero size.

Author: lexmag

lib/elixir/lib/macro.ex

@@ -484,7 +484,7 @@ defmodule Macro do
     else
       result = Enum.map_join(parts, ", ", fn(part) ->
         str = bitpart_to_string(part, fun)
-        if String.first(str) == "<" or String.last(str) == ">" do
+        if :binary.first(str) == ?< or :binary.last(str) == ?> do
           "(" <> str <> ")"
         else
           str