Hard-deprecate the Set module (#5513)

It will be removed in Elixir 2.0.

Author: whatyouhide

lib/elixir/lib/set.ex

@@ -9,7 +9,9 @@ defmodule Set do
   @type values :: [ value ]
   @type t :: map
 
-  # TODO: Deprecate every function by 1.4
+  # TODO: Remove by 2.0
+  # (hard-deprecated in elixir_dispatch)
+
   defmacrop target(set) do
     quote do
       case unquote(set) do

lib/elixir/src/elixir_dispatch.erl

@@ -353,5 +353,8 @@ deprecation('Elixir.HashSet', _, _) ->
   "use the MapSet module instead";
 deprecation('Elixir.Dict', _, _) ->
   "use the Map module for working with maps or the Keyword module for working with keyword lists";
+deprecation('Elixir.Set', _, _) ->
+  "use the MapSet module for working with sets";
+
 deprecation(_, _, _) ->
   false.