From a40c8cfb68f75c22c0082714d99e9c3a24a31051 Mon Sep 17 00:00:00 2001
From: Rhett Aultman <roadriverrail@gmail.com>
Date: Fri, 14 Apr 2017 07:48:59 -0700
Subject: Warn on unused local variables

Analyze functions for all local variables, parameters, and named
return variables which are never used in the function, and issue
a warning.
---
 libsolidity/analysis/StaticAnalyzer.cpp | 39 +++++++++++++++++++++++++++++++++
 libsolidity/analysis/StaticAnalyzer.h   |  6 +++++
 2 files changed, 45 insertions(+)

(limited to 'libsolidity/analysis')

diff --git a/libsolidity/analysis/StaticAnalyzer.cpp b/libsolidity/analysis/StaticAnalyzer.cpp
index 190d2420..55e7cb59 100644
--- a/libsolidity/analysis/StaticAnalyzer.cpp
+++ b/libsolidity/analysis/StaticAnalyzer.cpp
@@ -48,13 +48,52 @@ void StaticAnalyzer::endVisit(ContractDefinition const&)
 
 bool StaticAnalyzer::visit(FunctionDefinition const& _function)
 {
+	if (_function.isImplemented())
+		m_inFunction = true;
+	m_localVarUseCount.clear();
 	m_nonPayablePublic = _function.isPublic() && !_function.isPayable();
 	return true;
 }
 
 void StaticAnalyzer::endVisit(FunctionDefinition const&)
 {
+	m_inFunction = false;
 	m_nonPayablePublic = false;
+	for (auto const& var: m_localVarUseCount)
+		if (var.second == 0)
+			warning(var.first->location(), "Unused local variable");
+}
+
+bool StaticAnalyzer::visit(Identifier const& _identifier)
+{
+	if (m_inFunction)
+	{
+		if (auto var = dynamic_cast<VariableDeclaration const*>(_identifier.annotation().referencedDeclaration))
+		{
+			solAssert(!var->name().empty(), "");
+			if (var->isLocalVariable())
+				m_localVarUseCount[var] += 1;
+		}
+	}
+	return true;
+}
+
+bool StaticAnalyzer::visit(VariableDeclaration const& _variable)
+{
+	if (m_inFunction)
+	{
+		solAssert(_variable.isLocalVariable(), "");
+		if (_variable.name() != "")
+		{
+			// The variable may have been used before reaching the
+			// declaration.  If it was, we must not reset the counter,
+			// but since [] will insert the default 0, we really just
+			// need to access the map here and let it do the rest on its
+			// own.
+			m_localVarUseCount[&_variable];
+		}
+	}
+	return true;
 }
 
 bool StaticAnalyzer::visit(ExpressionStatement const& _statement)
diff --git a/libsolidity/analysis/StaticAnalyzer.h b/libsolidity/analysis/StaticAnalyzer.h
index 84342322..134ff95a 100644
--- a/libsolidity/analysis/StaticAnalyzer.h
+++ b/libsolidity/analysis/StaticAnalyzer.h
@@ -61,6 +61,8 @@ private:
 	virtual void endVisit(FunctionDefinition const& _function) override;
 
 	virtual bool visit(ExpressionStatement const& _statement) override;
+	virtual bool visit(VariableDeclaration const& _variable) override;
+	virtual bool visit(Identifier const& _identifier) override;
 
 	virtual bool visit(MemberAccess const& _memberAccess) override;
 
@@ -71,6 +73,10 @@ private:
 
 	/// Flag that indicates whether a public function does not contain the "payable" modifier.
 	bool m_nonPayablePublic = false;
+
+	std::map<VariableDeclaration const*, int> m_localVarUseCount;
+
+	bool m_inFunction = false;
 };
 
 }
-- 
cgit