Keep parameterized types as tuples of tuples, closes #4419

Author: josevalim

lib/ecto/enum.ex

@@ -314,8 +314,8 @@ defmodule Ecto.Enum do
 
   def mappings(types, field) when is_map(types) do
     case types do
-      %{^field => {:parameterized, Ecto.Enum, %{mappings: mappings}}} -> mappings
-      %{^field => {_, {:parameterized, Ecto.Enum, %{mappings: mappings}}}} -> mappings
+      %{^field => {:parameterized, {Ecto.Enum, %{mappings: mappings}}}} -> mappings
+      %{^field => {_, {:parameterized, {Ecto.Enum, %{mappings: mappings}}}}} -> mappings
       %{^field => _} -> raise ArgumentError, "#{field} is not an Ecto.Enum field"
       %{} -> raise ArgumentError, "#{field} does not exist"
     end

lib/ecto/parameterized_type.ex

@@ -193,7 +193,7 @@ defmodule Ecto.ParameterizedType do
   Useful when manually initializing a type for schemaless changesets.
   """
   def init(type, opts) do
-    {:parameterized, type, type.init(opts)}
+    {:parameterized, {type, type.init(opts)}}
   end
 
   @doc false