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diff --git a/libyul/AsmScope.h b/libyul/AsmScope.h
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+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * Scopes for identifiers.
+ */
+
+#pragma once
+
+#include <liblangutil/Exceptions.h>
+
+#include <libyul/YulString.h>
+
+#include <libdevcore/Visitor.h>
+
+#include <boost/variant.hpp>
+#include <boost/optional.hpp>
+
+#include <functional>
+#include <memory>
+
+namespace yul
+{
+
+struct Scope
+{
+	using YulType = YulString;
+	using LabelID = size_t;
+
+	struct Variable { YulType type; };
+	struct Label { };
+	struct Function
+	{
+		std::vector<YulType> arguments;
+		std::vector<YulType> returns;
+	};
+
+	using Identifier = boost::variant<Variable, Label, Function>;
+	using Visitor = dev::GenericVisitor<Variable const, Label const, Function const>;
+	using NonconstVisitor = dev::GenericVisitor<Variable, Label, Function>;
+
+	bool registerVariable(YulString _name, YulType const& _type);
+	bool registerLabel(YulString _name);
+	bool registerFunction(
+		YulString _name,
+		std::vector<YulType> const& _arguments,
+		std::vector<YulType> const& _returns
+	);
+
+	/// Looks up the identifier in this or super scopes and returns a valid pointer if found
+	/// or a nullptr if not found. Variable lookups up across function boundaries will fail, as
+	/// will any lookups across assembly boundaries.
+	/// The pointer will be invalidated if the scope is modified.
+	/// @param _crossedFunction if true, we already crossed a function boundary during recursive lookup
+	Identifier* lookup(YulString _name);
+	/// Looks up the identifier in this and super scopes (will not find variables across function
+	/// boundaries and generally stops at assembly boundaries) and calls the visitor, returns
+	/// false if not found.
+	template <class V>
+	bool lookup(YulString _name, V const& _visitor)
+	{
+		if (Identifier* id = lookup(_name))
+		{
+			boost::apply_visitor(_visitor, *id);
+			return true;
+		}
+		else
+			return false;
+	}
+	/// @returns true if the name exists in this scope or in super scopes (also searches
+	/// across function and assembly boundaries).
+	bool exists(YulString _name) const;
+
+	/// @returns the number of variables directly registered inside the scope.
+	size_t numberOfVariables() const;
+	/// @returns true if this scope is inside a function.
+	bool insideFunction() const;
+
+	Scope* superScope = nullptr;
+	/// If true, variables from the super scope are not visible here (other identifiers are),
+	/// but they are still taken into account to prevent shadowing.
+	bool functionScope = false;
+	std::map<YulString, Identifier> identifiers;
+};
+
+}