And the end-to-end example compiles!

.gitignore

@@ -2,3 +2,4 @@ build/*
 vendor/libtorch
 *.zip
 nimcache/*
+*.pt

flambeau/raw_bindings/serialize.nim

@@ -5,7 +5,10 @@
 #   * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
-import ./tensors, ./neural_nets
+import
+  ../cpp/std_cpp,
+  ./tensors,
+  ./neural_nets
 
 # (Almost) raw bindings to PyTorch serialization
 # -----------------------------------------------------------------------
@@ -31,4 +34,4 @@ import ./tensors, ./neural_nets
 # #######################################################################
 # libtorch/include/torch/csrc/api/include/torch/optim/optimizer.h
 
-proc save*(module: Module, path: cstring){.sideeffect, importcpp:"torch::save(@)".}
+proc save*[T](module: CppSharedPtr[T], path: cstring){.sideeffect, importcpp:"torch::save(@)".}

proof_of_concepts/poc09_end_to_end.nim

@@ -5,24 +5,14 @@ import
   ../flambeau,
   std/[enumerate, strformat]
 
-# Argh, need Linear{nullptr} in the codegen
-# so we cheat by inlining C++
-#
-# type Net {.pure.} = object of Module
-#
-#   fc1: Linear
-#   fc2: Linear
-#   fc3: Linear
+# Net is defined in poc_09_end_to_end_types.nim.hpp
+# to work around https://github.com/nim-lang/Nim/issues/16664
+# which workarounds https://github.com/nim-lang/Nim/issues/4687
 
-{.emit:["""
-struct Net: public torch::nn::Module {
-  torch::nn::Linear fc1{nullptr};
-  torch::nn::Linear fc2{nullptr};
-  torch::nn::Linear fc3{nullptr};
-};
-"""].}
-
-type Net{.pure, importcpp.} = object of Module
+type Net
+  {.pure, importcpp,
+    header:"poc09_end_to_end_types.nim.hpp".}
+    = object of Module
   fc1: Linear
   fc2: Linear
   fc3: Linear
@@ -72,6 +62,6 @@ proc main() =
       if batch_index mod 100 == 0:
         echo &"Epoch: {epoch} | Batch: {batch_index} | Loss: {loss.item(float32)}"
         # Serialize your model periodically as a checkpoint.
-        net.save("net.pt")
+        save(net, "net.pt")
 
 main()

proof_of_concepts/poc09_end_to_end_types.nim.hpp

@@ -0,0 +1,22 @@
+// We need Linear{nullptr} in the codegen
+// so we would like to cheat by inlining C++
+//
+// type Net {.pure.} = object of Module
+//
+//   fc1: Linear
+//   fc2: Linear
+//   fc3: Linear
+//
+// https://github.com/nim-lang/Nim/issues/4687
+//
+// However
+// due to https://github.com/nim-lang/Nim/issues/16664
+// it needs to be in its own file
+
+#include <torch/torch.h>
+
+struct Net: public torch::nn::Module {
+  torch::nn::Linear fc1{nullptr};
+  torch::nn::Linear fc2{nullptr};
+  torch::nn::Linear fc3{nullptr};
+};