diff --git a/kinda_example/lib/kinda_example_native.ex b/kinda_example/lib/kinda_example_native.ex
new file mode 100644
index 0000000..5f511f8
--- /dev/null
+++ b/kinda_example/lib/kinda_example_native.ex
@@ -0,0 +1,17 @@
+defmodule KindaExample.Native do
+  def check!({:kind, mod, ref}) when is_atom(mod) and is_reference(ref) do
+    struct!(mod, %{ref: ref})
+  end
+
+  def check!({:error, e}), do: raise(e)
+  def check!(ret), do: ret
+
+  def to_term(%mod{ref: ref}) do
+    forward(mod, :primitive, [ref])
+  end
+
+  def forward(element_kind, kind_func_name, args) do
+    apply(KindaExample.NIF, Module.concat(element_kind, kind_func_name), args)
+    |> check!()
+  end
+end
diff --git a/kinda_example/lib/kinda_exmaple_nif.ex b/kinda_example/lib/kinda_example_nif.ex
similarity index 84%
rename from kinda_example/lib/kinda_exmaple_nif.ex
rename to kinda_example/lib/kinda_example_nif.ex
index 89d870d..168f522 100644
--- a/kinda_example/lib/kinda_exmaple_nif.ex
+++ b/kinda_example/lib/kinda_example_nif.ex
@@ -4,8 +4,7 @@ defmodule KindaExample.NIF do
           root: __MODULE__,
           forward: KindaExample.Native
   defmodule CInt do
-    use Kinda.ResourceKind,
-      forward_module: KindaExample.Native
+    use Kinda.ResourceKind, forward_module: KindaExample.Native
   end
 
   for path <-
@@ -16,6 +15,10 @@ defmodule KindaExample.NIF do
     @external_resource path
   end
 
+  defmodule StrInt do
+    use Kinda.ResourceKind, forward_module: KindaExample.Native
+  end
+
   @on_load :load_nif
 
   def load_nif do
diff --git a/kinda_example/lib/kinda_exmaple_native.ex b/kinda_example/lib/kinda_exmaple_native.ex
deleted file mode 100644
index 037fd45..0000000
--- a/kinda_example/lib/kinda_exmaple_native.ex
+++ /dev/null
@@ -1,27 +0,0 @@
-defmodule KindaExample.Native do
-  def check!(ret) do
-    case ret do
-      {:kind, mod, ref} when is_atom(mod) and is_reference(ref) ->
-        struct!(mod, %{ref: ref})
-
-      {:error, e} ->
-        raise e
-
-      _ ->
-        ret
-    end
-  end
-
-  def to_term(%mod{ref: ref}) do
-    forward(mod, :primitive, [ref])
-  end
-
-  def forward(
-        element_kind,
-        kind_func_name,
-        args
-      ) do
-    apply(KindaExample.NIF, Module.concat(element_kind, kind_func_name), args)
-    |> check!()
-  end
-end
diff --git a/kinda_example/test/kinda_example_test.exs b/kinda_example/test/kinda_example_test.exs
index 72d5c49..be558dc 100644
--- a/kinda_example/test/kinda_example_test.exs
+++ b/kinda_example/test/kinda_example_test.exs
@@ -1,29 +1,27 @@
 defmodule KindaExampleTest do
   use ExUnit.Case
 
+  alias KindaExample.{NIF, Native}
+
   test "add in c" do
     assert 3 ==
-             KindaExample.NIF.kinda_example_add(1, 2)
-             |> KindaExample.Native.to_term()
+             NIF.kinda_example_add(1, 2) |> Native.to_term()
 
     assert match?(
              %Kinda.CallError{message: "Fail to fetch argument #2", error_return_trace: _},
-             catch_error(KindaExample.NIF.kinda_example_add(1, "2"))
+             catch_error(NIF.kinda_example_add(1, "2"))
            )
   end
 
   test "custom make" do
-    assert KindaExample.Native.forward(
-             KindaExample.NIF.CInt,
-             :make,
-             [100]
-           )
-           |> KindaExample.NIF."Elixir.KindaExample.NIF.CInt.primitive"() == 100
+    assert 100 ==
+             Native.forward(NIF.CInt, :make, [100])
+             |> NIF."Elixir.KindaExample.NIF.CInt.primitive"()
 
-    e = catch_error(KindaExample.NIF."Elixir.KindaExample.NIF.StrInt.make"(1))
+    e = catch_error(NIF."Elixir.KindaExample.NIF.StrInt.make"(1))
     assert Exception.message(e) =~ "Function clause error\n#{IO.ANSI.reset()}"
 
-    err = catch_error(KindaExample.NIF."Elixir.KindaExample.NIF.StrInt.make"(1))
+    err = catch_error(NIF."Elixir.KindaExample.NIF.StrInt.make"(1))
     # only test this on macOS, it will crash on Linux
     txt = Exception.message(err)
 
@@ -36,8 +34,11 @@ defmodule KindaExampleTest do
 
     assert match?(%Kinda.CallError{message: "Function clause error", error_return_trace: _}, err)
 
-    assert KindaExample.NIF."Elixir.KindaExample.NIF.StrInt.make"("1")
-           |> KindaExample.NIF."Elixir.KindaExample.NIF.CInt.primitive"() ==
-             1
+    assert 1 ==
+             NIF."Elixir.KindaExample.NIF.StrInt.make"("1")
+             |> NIF."Elixir.KindaExample.NIF.CInt.primitive"()
+
+    %NIF.StrInt{ref: ref} = NIF.StrInt.make("1")
+    assert 1 == ref |> NIF."Elixir.KindaExample.NIF.CInt.primitive"()
   end
 end
diff --git a/lib/codegen/kind_decl.ex b/lib/codegen/kind_decl.ex
index 89b39f1..eea4f7e 100644
--- a/lib/codegen/kind_decl.ex
+++ b/lib/codegen/kind_decl.ex
@@ -1,7 +1,7 @@
 defmodule Kinda.CodeGen.KindDecl do
   require Logger
 
-  @primitive_types for t <- ~w{
+  @primitive_types ~w{
     bool
     c_int
     c_uint
@@ -17,8 +17,7 @@ defmodule Kinda.CodeGen.KindDecl do
     u64
     u8
     usize
-  },
-                       do: String.to_atom(t)
+  }a
 
   @opaque_ptr {:optional_type, {:ref, [:*, :anyopaque]}}
   @opaque_array {:optional_type, {:ref, [:*, :const, :anyopaque]}}
diff --git a/lib/kinda_codegen.ex b/lib/kinda_codegen.ex
index 5b6cce9..038ebb2 100644
--- a/lib/kinda_codegen.ex
+++ b/lib/kinda_codegen.ex
@@ -16,7 +16,7 @@ defmodule Kinda.CodeGen do
     end
   end
 
-  @callback kinds() :: KindDecl.t()
+  @callback kinds() :: [KindDecl.t()]
   @callback nifs() :: [{atom(), integer()}]
   def kinds(), do: []