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diff --git a/libsolidity/formal/VariableUsage.h b/libsolidity/formal/VariableUsage.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/>.
+*/
+
+#pragma once
+
+#include <map>
+#include <set>
+#include <vector>
+
+namespace dev
+{
+namespace solidity
+{
+
+class ASTNode;
+class Declaration;
+
+/**
+ * This class collects information about which local variables of value type
+ * are modified in which parts of the AST.
+ */
+class VariableUsage
+{
+public:
+	explicit VariableUsage(ASTNode const& _node);
+
+	std::vector<Declaration const*> touchedVariables(ASTNode const& _node) const;
+
+private:
+	// Variable touched by a specific AST node.
+	std::map<ASTNode const*, Declaration const*> m_touchedVariable;
+	std::map<ASTNode const*, std::vector<ASTNode const*>> m_children;
+};
+
+}
+}