From 1e26ca8b8c669a7b3b2e2367439c6e0f840ed451 Mon Sep 17 00:00:00 2001
From: Bart Janssens <bart@bartjanssens.org>
Date: Sat, 1 Jun 2024 14:10:36 +0200
Subject: [PATCH] Fix static inheritance problem (#157)

Issue Regression with 0.12.3 in the support of static inheritance #156
---
 examples/inheritance.cpp       | 14 ++++++++++++++
 include/jlcxx/jlcxx_config.hpp |  2 +-
 include/jlcxx/module.hpp       | 12 +++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/examples/inheritance.cpp b/examples/inheritance.cpp
index 56e1f51..db5b832 100644
--- a/examples/inheritance.cpp
+++ b/examples/inheritance.cpp
@@ -59,6 +59,13 @@ std::string take_ref(A& a)
   return a.message();
 }
 
+// Static inheritance test (issue #156)
+struct StaticBase {
+};
+
+struct StaticDerived: public StaticBase {
+};
+
 // Example based on https://discourse.julialang.org/t/simplest-way-to-wrap-virtual-c-class/4977
 namespace virtualsolver
 {
@@ -100,6 +107,10 @@ namespace jlcxx
 
   template<> struct SuperType<virtualsolver::E> { typedef virtualsolver::Base type; };
   template<> struct SuperType<virtualsolver::F> { typedef virtualsolver::Base type; };
+
+  template<> struct IsMirroredType<StaticBase> : std::false_type { };
+  template<> struct IsMirroredType<StaticDerived> : std::false_type { };
+  template<> struct SuperType<StaticDerived> { typedef StaticBase type; };
 }
 
 JLCXX_MODULE define_types_module(jlcxx::Module& types)
@@ -121,6 +132,9 @@ JLCXX_MODULE define_types_module(jlcxx::Module& types)
   types.method("dynamic_message_c", [](const A& c) { return dynamic_cast<const C*>(&c)->data; });
 
   types.method("take_ref", take_ref);
+
+  types.add_type<StaticBase>("StaticBase");
+  types.add_type<StaticDerived>("StaticDerived", jlcxx::julia_base_type<StaticBase>());
 }
 
 JLCXX_MODULE define_vsolver_module(jlcxx::Module& vsolver_mod)
diff --git a/include/jlcxx/jlcxx_config.hpp b/include/jlcxx/jlcxx_config.hpp
index 4b68ea9..5922cbf 100644
--- a/include/jlcxx/jlcxx_config.hpp
+++ b/include/jlcxx/jlcxx_config.hpp
@@ -15,7 +15,7 @@
 
 #define JLCXX_VERSION_MAJOR 0
 #define JLCXX_VERSION_MINOR 12
-#define JLCXX_VERSION_PATCH 3
+#define JLCXX_VERSION_PATCH 4
 
 // From https://stackoverflow.com/questions/5459868/concatenate-int-to-string-using-c-preprocessor
 #define __JLCXX_STR_HELPER(x) #x
diff --git a/include/jlcxx/module.hpp b/include/jlcxx/module.hpp
index 0726542..3a35f78 100644
--- a/include/jlcxx/module.hpp
+++ b/include/jlcxx/module.hpp
@@ -1035,7 +1035,17 @@ struct DownCast
 {
   static inline void apply(Module& mod)
   {
-    mod.method("cxxdowncast", [](SingletonType<DerivedT>, SuperT* base) { return dynamic_cast<DerivedT*>(base); });
+    mod.method("cxxdowncast", [](SingletonType<DerivedT>, SuperT* base)
+    {
+      if constexpr (std::is_polymorphic<DerivedT>::value)
+      {
+        return dynamic_cast<DerivedT*>(base);
+      }
+      else
+      {
+        return static_cast<DerivedT*>(base);
+      }
+    });
     using newsuper_t = supertype<SuperT>;
     if constexpr (!std::is_same<newsuper_t,SuperT>::value)
     {