Shader: Improve attribute source location

include/Nazara/Shader/Ast/ExpressionValue.hpp

@@ -0,0 +1,52 @@
+// Copyright (C) 2022 Jérôme "Lynix" Leclercq (lynix680@gmail.com)
+// This file is part of the "Nazara Engine - Shader module"
+// For conditions of distribution and use, see copyright notice in Config.hpp
+
+#pragma once
+
+#ifndef NAZARA_SHADER_AST_EXPRESSIONVALUE_HPP
+#define NAZARA_SHADER_AST_EXPRESSIONVALUE_HPP
+
+#include <Nazara/Prerequisites.hpp>
+#include <Nazara/Shader/Ast/Enums.hpp>
+#include <variant>
+
+namespace Nz::ShaderAst
+{
+	struct Expression;
+
+	using ExpressionPtr = std::unique_ptr<Expression>;
+
+	template<typename T>
+	class ExpressionValue
+	{
+		public:
+			ExpressionValue() = default;
+			ExpressionValue(T value);
+			ExpressionValue(ExpressionPtr expr);
+			ExpressionValue(const ExpressionValue&) = default;
+			ExpressionValue(ExpressionValue&&) noexcept = default;
+			~ExpressionValue() = default;
+
+			ExpressionPtr&& GetExpression() &&;
+			const ExpressionPtr& GetExpression() const &;
+			const T& GetResultingValue() const;
+
+			bool IsExpression() const;
+			bool IsResultingValue() const;
+
+			bool HasValue() const;
+
+			void Reset();
+
+			ExpressionValue& operator=(const ExpressionValue&) = default;
+			ExpressionValue& operator=(ExpressionValue&&) noexcept = default;
+
+		private:
+			std::variant<std::monostate, T, ExpressionPtr> m_value;
+	};
+}
+
+#include <Nazara/Shader/Ast/ExpressionValue.inl>
+
+#endif // NAZARA_SHADER_AST_EXPRESSIONVALUE_HPP