Started `boxed::Box<T>`.

Fortune for libexopt's current commit: Future blessing − 末吉

include/boxed.h

@@ -0,0 +1,86 @@
+
+#pragma once
+
+#include <memory>
+#include <utility>
+
+#include "pointer.h"
+#include "util.hh"
+
+#include "exopt.h"
+
+namespace exopt::types { namespace boxed {
+	template<typename T>
+	struct [[gnu::visibility("internal")]]  boxable_value_type { using type = std::conditional_t
+			<std::is_reference_v<T>
+			,std::reference_wrapper<std::remove_cvref_t<T> >
+			,T>; };
+
+	template<typename T>
+	constexpr std::unique_ptr<T> uniq_clone(std::unique_ptr<T> const& c) noexcept(std::is_nothrow_copy_constructible_v<T>) requires(std::is_copy_constructible_v<T>)
+	{ if(__builtin_expect(bool(c), true)) return std::make_unique<T>(*c); return nullptr; }
+
+	template<typename T>
+	constexpr std::unique_ptr<T> uniq_clone_unsafe(std::unique_ptr<T> const& c)
+#ifndef DEBUG
+		noexcept(std::is_nothrow_copy_constructible_v<T>) 
+#endif
+		requires(std::is_copy_constructible_v<T>)
+	{ if(__builtin_expect(!bool(c), false)) 
+#ifdef DEBUG
+		throw ptr::NullException{}; 
+#else
+		__builtin_unreachable(); 
+#endif
+	return std::make_unique<T>(*c); }
+
+
+	template<typename T>
+	struct Box {
+		typedef boxable_value_type<T>::type type;
+
+		constexpr Box() noexcept(std::is_nothrow_default_constructible_v<T>) requires(std::is_default_constructible_v<T>)
+			: m_ptr{std::make_unique<T>()} {}
+
+		template<typename... Args> requires(std::is_constructible_v<T, Args...>)
+		constexpr Box(Args&&... ctor) noexcept(std::is_nothrow_constructible_v<T, Args...>)
+			: m_ptr{std::make_unique<T>(std::forward<Args>(ctor)...)} {}
+
+		constexpr Box(T&& value) noexcept(std::is_nothrow_constructible_v<T>)
+			: m_ptr{std::make_unique<T>(std::move(value))} {}
+
+		constexpr Box(Box&&) noexcept = default;
+		constexpr Box& operator=(Box&&) noexcept = default;
+		constexpr Box(const Box& copy) noexcept(std::is_nothrow_copy_constructible_v<T>) requires(std::is_copy_constructible_v<T>)
+			: m_ptr{uniq_clone_unsafe(copy.m_ptr)} {}
+		constexpr Box& operator=(Box const& copy) noexcept(std::is_nothrow_copy_assignable_v<T>) requires(std::is_copy_assignable_v<T>)
+		{
+			if(__builtin_expect(this != std::addressof(copy), true)) {
+				m_ptr = uniq_clone_unsafe(copy.m_ptr);
+			} return *this;
+		}
+
+	//TODO: Accessors, `(explicit?) operator std::unique_ptr<T> const&[&]`?, etc.
+
+		constexpr ~Box() = default;
+	private:
+		std::unique_ptr<T> m_ptr; // Unique<T> m_ptr;
+	};
+}
+using boxed::Box;
+}
+
+namespace exopt::types { namespace optional [[gnu::visibility("internal")]] {
+	template<typename T>
+	struct null_optimise<boxed::Box<T> > { constexpr static inline bool value = true;
+	//XXX: Eh.. Idk if Option<T>'s lifetime design can make this work...
+		using held_type = boxed::Box<T>;
+		using type = boxed::Box<T>&;
+		constexpr static decltype(auto) convert_to_held(std::add_rvalue_reference_t<type> t) noexcept { return std::move(t); }
+		constexpr static decltype(auto) convert_from_held(std::add_rvalue_reference_t<held_type> t) noexcept { return std::forward<type>(t); }
+
+		constexpr static inline T* sentinel = nullptr;
+	};
+
+
+}

include/either.hh

@@ -119,6 +119,26 @@ namespace exopt::types {
 			}
 			//TODO: ^ UNLIKELY(is_empty()) null-checks for `*arg`.
 
+			constexpr reference_type operator*() & noexcept {
+				return as_ref();
+			}
+
+			constexpr move_reference_type operator*() && noexcept {
+				return as_ref();
+			}
+
+			constexpr const_reference_type operator*() const noexcept {
+				return as_ref();
+			}
+
+			constexpr pointer_type operator->() noexcept {
+				return get();
+			}
+
+			constexpr const_pointer_type operator->() noexcept {
+				return get();
+			}
+
 			constexpr const_pointer_type get() const noexcept {
 				return std::visit([](const auto& arg) -> const_pointer_type {
 					using U = std::remove_cvref_t<decltype(arg)>;
@@ -127,6 +147,7 @@ namespace exopt::types {
 					else 	return arg;
 				}, m_value);
 			}
+
 			constexpr pointer_type get() noexcept {
 				return std::addressof(make_owned());
 				/*
@@ -137,6 +158,7 @@ namespace exopt::types {
 					else 	return arg;
 				}, m_value);*/
 			}
+
 			constexpr reference_type make_owned() & noexcept(NTWriteable) requires(Writeable) {
 				if(const auto* ct_from = std::visit([&m_value](auto& arg) -> auto* {
 					using U = std::remove_cvref_t<decltype(arg)>;
@@ -148,6 +170,7 @@ namespace exopt::types {
 
 				}, m_value)) return m_value.emplace<value_type>(*ct_from); //XXX: Do we need to create a temporary here for creating invariants by reading the old invariant?
 			}
+
 			constexpr move_reference_type make_owned() && noexcept(NTWriteable) requires(Writeable) {
 				if(const auto* ct_from = std::visit([&m_value](auto&& arg) -> auto* {
 					using U = std::remove_cvref_t<decltype(arg)>;
@@ -161,10 +184,10 @@ namespace exopt::types {
 				}, std::move(m_value))) return std::move(m_value.emplace<value_type>(*ct_from)); //XXX: Do we need to create a temporary here for creating invariants by reading the old invariant?
 			}
 
-
 			//These commented out visits modify the pointee of the borrowed invariant. THIS IS NOT WHAT WE WANT. Instead, we emplace a copy and then copy it again (possibly elided: &) or return it as an rvalue reference (elided: &&)
 			constexpr value_type into_owned() & noexcept(NTWriteable) requires(Writeable) {
 				return make_owned();
+
 				/*return std::visit([](auto&& arg) -> move_reference_type {
 					using U = std::remove_cvref_t<decltype(arg)>;
 					if constexpr(std::is_same_v<U, value_type>)
@@ -172,6 +195,7 @@ namespace exopt::types {
 					else 	return std::move(*arg);
 				}, std::move(m_value));*/
 			}
+
 			constexpr move_reference_type into_owned() && noexcept(NTWriteable) requires(Writeable) {
 				return make_owned();
 				/*return std::move(std::visit([](auto&& arg) -> move_reference_type {
@@ -194,6 +218,9 @@ namespace exopt::types {
 			var_t m_value;
 		};
 
+		//template<typename T>
+		//TODO: We want it to work: class Cow<std::unique_ptr<T>> : public Cow<T> {};
+#if 0
 		template<typename T>
 		class Cow<std::shared_ptr<T>> {
 			using var_t = std::variant<
@@ -214,6 +241,7 @@ namespace exopt::types {
 		private:
 			var_t m_value;
 		};
+#endif
 	}
 
 	/// Manually lifetime managed Cow<T>
@@ -222,4 +250,8 @@ namespace exopt::types {
 	/// RC-lifetime managed Cow<T>
 	template<typename T>
 	using RcCow = Cow<std::shared_ptr<T>>;
+
+	/// Boxed unique Cow<T> 
+	template<typename T>
+	using BoxCow = Cow<std::unique_ptr<T>>;
 }

include/pointer.h

@@ -143,7 +143,7 @@ namespace exopt::ptr {
 	};
 
 	template<typename T> requires(!std::is_reference_v<T>)
-	struct NonNull final {
+	struct NonNull {
 
 		using pointer_type = T*;
 		using const_pointer_type = std::remove_cv_t<T> const*;