From 8e31ef9905ba14bed6069139dde38c05a70a2a39 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Tue, 18 Apr 2023 22:02:47 +0300
Subject: [PATCH] BAN: Add specialization for ErrorOr<LValueReference>

ErrorOr can now return a reference :)
---
 BAN/include/BAN/Errors.h | 27 +++++++++++++++++++++++++++
 BAN/include/BAN/Traits.h |  1 +
 2 files changed, 28 insertions(+)

diff --git a/BAN/include/BAN/Errors.h b/BAN/include/BAN/Errors.h
index 63674add32..52ec5f27ac 100644
--- a/BAN/include/BAN/Errors.h
+++ b/BAN/include/BAN/Errors.h
@@ -85,6 +85,33 @@ namespace BAN
 		Variant<Error, T> m_data;
 	};
 
+	template<lvalue_reference T>
+	class [[nodiscard]] ErrorOr<T>
+	{
+	public:
+		ErrorOr(T value)
+		{
+			m_data.template set<T>(value);
+		}
+		ErrorOr(Error&& error)
+			: m_data(move(error))
+		{ }
+		ErrorOr(const Error& error)
+			: m_data(error)
+		{ }
+
+		bool is_error() const			{ return m_data.template has<Error>(); }
+		Error& error()					{ return m_data.template get<Error>(); }
+		const Error& error() const		{ return m_data.template get<Error>(); }
+		T value()						{ return m_data.template get<T>(); }
+
+		Error release_error()			{ return move(error()); m_data.clear(); }
+		T release_value()				{ return value(); m_data.clear(); }
+
+	private:
+		Variant<Error, T> m_data;
+	};
+
 	template<>
 	class [[nodiscard]] ErrorOr<void>
 	{
diff --git a/BAN/include/BAN/Traits.h b/BAN/include/BAN/Traits.h
index de72338843..0a9ca4f3b6 100644
--- a/BAN/include/BAN/Traits.h
+++ b/BAN/include/BAN/Traits.h
@@ -40,6 +40,7 @@ namespace BAN
 	template<typename T> struct is_lvalue_reference		: false_type {};
 	template<typename T> struct is_lvalue_reference<T&>	: true_type {};
 	template<typename T> inline constexpr bool is_lvalue_reference_v = is_lvalue_reference<T>::value;
+	template<typename T> concept lvalue_reference = is_lvalue_reference_v<T>;
 
 	template<typename T> struct is_integral { static constexpr bool value = requires (T t, T* p, void (*f)(T)) { reinterpret_cast<T>(t); f(0); p + t; }; };
 	template<typename T> inline constexpr bool is_integral_v = is_integral<T>::value;