fix fasten hook to properly return errors

lib/construct/hooks/fasten.ex

@@ -63,11 +63,19 @@ defmodule Construct.Hooks.Fasten do
         cast_clause =
           quote do
             defp unquote(function_name)(%{unquote(to_string(name)) => term}, opts) do
-              Construct.Type.cast(unquote(type), term, opts)
+              case Construct.Type.cast(unquote(type), term, opts) do
+                {:ok, term} -> {:ok, term}
+                {:error, reason} -> {:error, %{unquote(name) => reason}}
+                :error -> {:error, %{unquote(name) => :invalid}}
+              end
             end
 
             defp unquote(function_name)(%{unquote(name) => term}, opts) do
-              Construct.Type.cast(unquote(type), term, opts)
+              case Construct.Type.cast(unquote(type), term, opts) do
+                {:ok, term} -> {:ok, term}
+                {:error, reason} -> {:error, %{unquote(name) => reason}}
+                :error -> {:error, %{unquote(name) => :invalid}}
+              end
             end
           end
 

test/integration/hooks/fasten_test.exs

@@ -0,0 +1,48 @@
+defmodule Construct.Integration.Hooks.FastenTest do
+  use Construct.TestCase
+
+  defmodule IP do
+    @behaviour Construct.Type
+
+    def cast(term) when is_binary(term) do
+      :inet.parse_address(String.to_charlist(term))
+    end
+
+    def cast(_) do
+      :error
+    end
+  end
+
+  defmodule User do
+    use Construct
+    use Construct.Hooks.Fasten
+
+    structure do
+      field :huid, :string
+      field :ip, IP
+    end
+  end
+
+  test "#make returns structs with anonymous functions" do
+    params = %{
+      "huid" => "9767dcf6-9413-44dd-af9a-2af0188ae12b",
+      "ip" => "127.0.0.1"
+    }
+
+    assert {:ok, %User{
+      huid: params["huid"],
+      ip: {127, 0, 0, 1}
+    }} == User.make(params)
+  end
+
+  test "#make with invalid params" do
+    assert {:error, %{huid: :invalid}} =
+      User.make(%{"huid" => 42, "ip" => 42})
+
+    assert {:error, %{huid: :invalid}} =
+      User.make(%{"huid" => 42, "ip" => "127.0.0.1.1"})
+
+    assert {:error, %{ip: :einval}} =
+      User.make(%{"huid" => "9767dcf6-9413-44dd-af9a-2af0188ae12b", "ip" => "127.0.0.1.1"})
+  end
+end