Define Record.options for each record with the allowed options

Closes #916, #857

Author: José Valim

lib/elixir/lib/record.ex

@@ -533,21 +533,32 @@ defmodule Record do
   ## Types/specs generation
 
   defp core_specs(values) do
-    types = lc { _, _, spec } inlist values, do: spec
+    types   = lc { _, _, spec } inlist values, do: spec
+    options = if values == [], do: [], else: [options_specs(values)]
 
     quote do
       unless Kernel.Typespec.defines_type?(__MODULE__, :t, 0) do
         @type t :: { __MODULE__, unquote_splicing(types) }
       end
 
+      unless Kernel.Typespec.defines_type?(__MODULE__, :options, 0) do
+        @type options :: unquote(options)
+      end
+
       @spec new :: t
-      @spec new(Keyword.t | tuple) :: t
-      @spec to_keywords(t) :: Keyword.t
-      @spec update(Keyword.t, t) :: t
+      @spec new(options | tuple) :: t
+      @spec to_keywords(t) :: options
+      @spec update(options, t) :: t
       @spec __index__(atom) :: non_neg_integer | nil
     end
   end
 
+  defp options_specs([{ k, _, v }|t]) do
+    :lists.foldl fn { k, _, v }, acc ->
+      { :|, [], { k, v }, acc }
+    end, { k, v }, t
+  end
+
   defp accessor_specs([{ :__exception__, _, _ }|t], 1, acc) do
     accessor_specs(t, 2, acc)
   end