Fix some typespecs (#173)

Co-authored-by: Gianluca Nitti <[email protected]>

Author: gianluca-nitti

lib/mongo.ex

@@ -70,8 +70,8 @@ defmodule Mongo do
 
   @type conn :: DbConnection.Conn
   @type collection :: String.t()
-  @opaque cursor :: Mongo.Cursor.t()
-  @type result(t) :: :ok | {:ok, t} | {:error, Mongo.Error.t()}
+  @type cursor :: Mongo.Cursor.t()
+  @type result(t) :: :ok | {:ok, t} | {:error, Mongo.Error.t()} | {:error, Mongo.WriteError.t()}
   @type result!(t) :: t
   @type initial_type :: :unknown | :single | :replica_set_no_primary | :sharded
 

lib/mongo/error.ex

@@ -217,6 +217,12 @@ end
 defmodule Mongo.WriteError do
   defexception [:n, :ok, :write_errors]
 
+  @type t :: %__MODULE__{
+          n: number,
+          ok: number,
+          write_errors: [map]
+        }
+
   def message(e) do
     "n: #{e.n}, ok: #{e.ok}, write_errors: #{inspect(e.write_errors)}"
   end