From 0f2d186fbd4cc637a359b1d62370174aebd2b80f Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Tue, 1 Oct 2024 23:38:01 +0200
Subject: Some work on maybe_uninit & option

---
 asl/annotations.hpp        | 12 ------------
 asl/maybe_uninit.hpp       | 41 ++++++++++++++++++++++++++++++-----------
 asl/maybe_uninit_tests.cpp |  9 ++++++++-
 asl/option.hpp             | 17 +++++++++++++++++
 asl/option_tests.cpp       | 11 ++++++++++-
 5 files changed, 65 insertions(+), 25 deletions(-)

(limited to 'asl')

diff --git a/asl/annotations.hpp b/asl/annotations.hpp
index c0d8f20..90e603f 100644
--- a/asl/annotations.hpp
+++ b/asl/annotations.hpp
@@ -9,15 +9,3 @@
 #else
     #define ASL_NO_UNIQUE_ADDRESS [[no_unique_address]]
 #endif
-
-namespace asl
-{
-
-struct unsafe
-{
-    unsafe() = delete;
-    explicit unsafe(auto&&) {}
-};
-
-} // namespace asl
-
diff --git a/asl/maybe_uninit.hpp b/asl/maybe_uninit.hpp
index ffbbb1c..19351d5 100644
--- a/asl/maybe_uninit.hpp
+++ b/asl/maybe_uninit.hpp
@@ -1,42 +1,61 @@
 #pragma once
 
-#include "asl/annotations.hpp"
 #include "asl/layout.hpp"
 #include "asl/memory.hpp"
 #include "asl/meta.hpp"
+#include "asl/utility.hpp"
 
 namespace asl
 {
 
 template<is_object T>
-class alignas(align_of<T>) maybe_uninit
+class maybe_uninit
 {
-    char m_storage[size_of<T>];
+    union
+    {
+        alignas(align_of<T>) char m_storage[size_of<T>];
+        T m_value;
+    };
 
 public:
-    constexpr void* uninit_ptr() const { return m_storage; }
+    constexpr maybe_uninit() {} // NOLINT(*-member-init)
+    
+    maybe_uninit(const maybe_uninit&) = delete;
+    maybe_uninit(maybe_uninit&&) = delete;
+
+    maybe_uninit& operator=(const maybe_uninit&) = delete;
+    maybe_uninit& operator=(maybe_uninit&&) = delete;
+    
+    constexpr ~maybe_uninit() = default;
+    constexpr ~maybe_uninit() requires (!trivially_destructible<T>) {}
+    
+    constexpr void*       uninit_ptr() && = delete;
+    constexpr const void* uninit_ptr() const& { return m_storage; }
+    constexpr void*       uninit_ptr() &      { return m_storage; }
 
     // @Safety Pointer must only be accessed when in initialized state.
-    constexpr const T* init_ptr(unsafe) const { return reinterpret_cast<const T*>(m_storage); }
-    constexpr       T* init_ptr(unsafe)       { return reinterpret_cast<      T*>(m_storage); }
+    constexpr       T* init_ptr_unsafe() && = delete;
+    constexpr const T* init_ptr_unsafe() const& { return &m_value; }
+    constexpr       T* init_ptr_unsafe() &      { return &m_value; }
 
     // @Safety Reference must only be accessed when in initialized state.
-    constexpr const T& as_init(unsafe) const { return *reinterpret_cast<const T*>(m_storage); }
-    constexpr       T& as_init(unsafe)       { return *reinterpret_cast<      T*>(m_storage); }
+    constexpr       T& as_init_unsafe() && = delete;
+    constexpr const T& as_init_unsafe() const& { return m_value; }
+    constexpr       T& as_init_unsafe() &      { return m_value; }
 
     // @Safety Must be called only when in uninitialized state.
     template<typename... Args>
-    inline void init(unsafe, Args&&... args)
+    constexpr void init_unsafe(Args&&... args) &
     {
         new(uninit_ptr()) T(ASL_FWD(args)...);
     }
 
     // @Safety Must be called only when in initialized state.
-    inline void uninit(unsafe)
+    constexpr void uninit_unsafe() &
     {
         if constexpr (!trivially_destructible<T>)
         {
-            init_ptr(unsafe("Caller has checked init state"))->~T();
+            init_ptr_unsafe()->~T();
         }
     }
 };
diff --git a/asl/maybe_uninit_tests.cpp b/asl/maybe_uninit_tests.cpp
index 7efeff0..7584eea 100644
--- a/asl/maybe_uninit_tests.cpp
+++ b/asl/maybe_uninit_tests.cpp
@@ -1,7 +1,14 @@
 #include "asl/maybe_uninit.hpp"
+#include "asl/test_types.hpp"
 
 static_assert(asl::layout::of<int>() == asl::layout::of<asl::maybe_uninit<int>>());
 static_assert(asl::size_of<int> == asl::size_of<asl::maybe_uninit<int>>);
 static_assert(asl::align_of<int> == asl::align_of<asl::maybe_uninit<int>>);
 
-int main() { return 0; }
+static_assert(asl::trivially_destructible<asl::maybe_uninit<TriviallyDestructible>>);
+static_assert(!asl::trivially_destructible<asl::maybe_uninit<HasDestructor>>);
+
+int main()
+{
+    return 0;
+}
diff --git a/asl/option.hpp b/asl/option.hpp
index e71eb57..4793830 100644
--- a/asl/option.hpp
+++ b/asl/option.hpp
@@ -1,13 +1,30 @@
 #pragma once
 
 #include "asl/meta.hpp"
+#include "asl/maybe_uninit.hpp"
 
 namespace asl
 {
 
+struct nullopt_t {};
+static constexpr nullopt_t nullopt{};
+
 template<is_object T>
 class option
 {
+    maybe_uninit<T> m_payload;
+    bool            m_has_value = false;
+
+public:
+    constexpr option() = default;
+    constexpr option(nullopt_t) {} // NOLINT(*-explicit-conversions)
+
+    constexpr ~option() = default;
+    constexpr ~option() requires (!trivially_destructible<T>)
+    {
+        if (m_has_value) { m_payload.uninit_unsafe(); }
+    }
+    
 };
 
 } // namespace asl
diff --git a/asl/option_tests.cpp b/asl/option_tests.cpp
index 41c67e1..ff63e1a 100644
--- a/asl/option_tests.cpp
+++ b/asl/option_tests.cpp
@@ -1,3 +1,12 @@
 #include "asl/option.hpp"
+#include "asl/test_types.hpp"
 
-int main() { return 0; }
+static_assert(asl::trivially_destructible<asl::option<TriviallyDestructible>>);
+static_assert(!asl::trivially_destructible<asl::option<HasDestructor>>);
+
+int main()
+{
+    asl::option<HasDestructor> a;
+    asl::option<TriviallyDestructible> b;
+    return 0;
+}
-- 
cgit