From ea290e120ee0069e0c4a983d49fb69fc942dc3f2 Mon Sep 17 00:00:00 2001
From: Benoit Germain <benoit.germain@ubisoft.com>
Date: Wed, 9 Oct 2024 09:43:24 +0200
Subject: Improved Unique<> implementation, moved StackIndex into a separate
 header

---
 src/compat.h       |  5 +----
 src/luaerrors.h    |  2 +-
 src/stackindex.hpp | 11 +++++++++++
 src/unique.hpp     | 33 +++++++++++++++++++++------------
 4 files changed, 34 insertions(+), 17 deletions(-)
 create mode 100644 src/stackindex.hpp

(limited to 'src')

diff --git a/src/compat.h b/src/compat.h
index 90e72a3..081e4c7 100644
--- a/src/compat.h
+++ b/src/compat.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "debug.h"
+#include "stackindex.hpp"
 
 // try to detect if we are building against LuaJIT or MoonJIT
 #if defined(LUA_JITLIBNAME)
@@ -32,10 +33,6 @@
 
 // #################################################################################################
 
-static constexpr StackIndex kIdxRegistry{ LUA_REGISTRYINDEX };
-
-// #################################################################################################
-
 // a strong-typed wrapper over lua types to see them easier in a debugger
 enum class LuaType
 {
diff --git a/src/luaerrors.h b/src/luaerrors.h
index cf04f6c..ef32c60 100644
--- a/src/luaerrors.h
+++ b/src/luaerrors.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "unique.hpp"
+#include "stackindex.hpp"
 
 // #################################################################################################
 
diff --git a/src/stackindex.hpp b/src/stackindex.hpp
new file mode 100644
index 0000000..7c2c17a
--- /dev/null
+++ b/src/stackindex.hpp
@@ -0,0 +1,11 @@
+#pragma once
+
+#include "unique.hpp"
+
+DECLARE_UNIQUE_TYPE(StackIndex, int);
+static_assert(std::is_trivial_v<StackIndex>);
+
+// #################################################################################################
+
+static constexpr StackIndex kIdxRegistry{ LUA_REGISTRYINDEX };
+static constexpr StackIndex kIdxTop{ -1 };
diff --git a/src/unique.hpp b/src/unique.hpp
index 846708e..829fa49 100644
--- a/src/unique.hpp
+++ b/src/unique.hpp
@@ -7,26 +7,39 @@ template <typename T, typename TAG, typename specialization = void>
 class Unique
 {
     private:
-    T val;
+    T val; // no default initialization so that std::is_trivial_v<Unique<T>> == true
 
     public:
     using type = T;
-    constexpr Unique() = default;
-    operator T() const { return val; }
-    Unique& operator=(T const&) = delete;
-    Unique& operator=(T&&) = delete;
-    explicit constexpr Unique(T b_)
+
+    ~Unique() = default;
+    constexpr explicit Unique(T b_)
     : val{ b_ }
     {
     }
+
+    // rule of 5
+    constexpr Unique() = default;
+    constexpr Unique(Unique const&) = default;
+    constexpr Unique(Unique&&) = default;
+    constexpr Unique& operator=(Unique const&) = default;
+    constexpr Unique& operator=(Unique&&) = default;
+
+    // can't implicitly affect from base type
+    Unique& operator=(T const&) = delete;
+    constexpr Unique& operator=(T&&) = delete;
+
+    // cast
+    constexpr operator T() const noexcept { return val; }
+
     // pre-increment
-    auto& operator++()
+    auto& operator++() noexcept
     {
         ++val;
         return *this;
     }
     // post-increment
-    auto operator++(int)
+    auto operator++(int) noexcept
     {
         return Unique<T, TAG>{ std::exchange(val, val + 1) };
     }
@@ -46,7 +59,3 @@ class Unique<T, TAG, std::enable_if_t<!std::is_scalar_v<T>>>
 };
 
 #define DECLARE_UNIQUE_TYPE(_name, _type) using _name = Unique<_type, class Unique_##_name##_Tag>
-
-// putting this here to break a header circular dependency until I find a better place
-DECLARE_UNIQUE_TYPE(StackIndex, int);
-static constexpr StackIndex kIdxTop{ -1 };
-- 
cgit v1.2.3-55-g6feb