From abad04b1af55fb2a45e3ab672f361bc72626f30b Mon Sep 17 00:00:00 2001
From: Bart Janssens <bart@bartjanssens.org>
Date: Tue, 26 Sep 2023 18:06:02 +0200
Subject: [PATCH] Don't store constants as references

Closes issue https://github.com/JuliaInterop/CxxWrap.jl/issues/374
---
 examples/types.cpp       | 4 ++++
 include/jlcxx/module.hpp | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/examples/types.cpp b/examples/types.cpp
index 89983d8..68c3b6f 100644
--- a/examples/types.cpp
+++ b/examples/types.cpp
@@ -367,6 +367,10 @@ JLCXX_MODULE define_julia_module(jlcxx::Module& types)
   types.set_const("EnumClassBlue", EnumClass::blue);
   types.method("check_red", [] (const EnumClass c) { return c == EnumClass::red; });
 
+  static const EnumClass stored_blue = EnumClass::blue;
+  types.method("check_enum_byref", [] (const EnumClass& c) { return c == EnumClass::red; });
+  types.set_const("StoredBlue", stored_blue);
+
   types.add_type<Foo>("Foo")
     .constructor<const std::wstring&, jlcxx::ArrayRef<double,1>>()
     .method("name", [](Foo& f) { return f.name; })
diff --git a/include/jlcxx/module.hpp b/include/jlcxx/module.hpp
index 933d994..ef83521 100644
--- a/include/jlcxx/module.hpp
+++ b/include/jlcxx/module.hpp
@@ -629,12 +629,13 @@ class JLCXX_API Module
   template<typename T>
   void set_const(const std::string& name, T&& value)
   {
-    static_assert(IsMirroredType<typename std::remove_reference<T>::type>::value, "set_const can only be applied to IsMirrored types (e.g. numbers or standard layout structs)");
+    using plain_type = remove_const_ref<T>;
+    static_assert(IsMirroredType<plain_type>::value, "set_const can only be applied to IsMirrored types (e.g. numbers or standard layout structs)");
     if(get_constant(name) != nullptr)
     {
       throw std::runtime_error("Duplicate registration of constant " + name);
     }
-    set_constant(name, box<T>(value));
+    set_constant(name, box<plain_type>(value));
   }
 
   std::string name() const