diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index 74d40da43..bc6be6008 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -83,7 +83,6 @@ map<FixedHash<4>, FunctionTypePointer> ContractDefinition::getInterfaceFunctions
 
 	map<FixedHash<4>, FunctionTypePointer> exportedFunctions;
 	for (auto const& it: exportedFunctionList)
-		// exportedFunctions.insert(make_pair(std::get<0>(it), FunctionDescription(std::get<1>(it), std::get<2>(it))));
 		exportedFunctions.insert(it);
 
 	solAssert(exportedFunctionList.size() == exportedFunctions.size(),
@@ -139,12 +138,12 @@ void ContractDefinition::checkIllegalOverrides() const
 	}
 }
 
-vector<pair<FixedHash<4>, shared_ptr<FunctionType const>>> const& ContractDefinition::getInterfaceFunctionList() const
+vector<pair<FixedHash<4>, FunctionTypePointer>> const& ContractDefinition::getInterfaceFunctionList() const
 {
 	if (!m_interfaceFunctionList)
 	{
 		set<string> functionsSeen;
-		m_interfaceFunctionList.reset(new vector<pair<FixedHash<4>, shared_ptr<FunctionType const>>>());
+		m_interfaceFunctionList.reset(new vector<pair<FixedHash<4>, FunctionTypePointer>>());
 		for (ContractDefinition const* contract: getLinearizedBaseContracts())
 		{
 			for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index 9ea6c144b..6c207290c 100755
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -156,6 +156,37 @@ private:
 	Declaration const* m_scope;
 };
 
+/**
+ * Abstract class that is added to each AST node that can store local variables.
+ */
+class VariableScope
+{
+public:
+	void addLocalVariable(VariableDeclaration const& _localVariable) { m_localVariables.push_back(&_localVariable); }
+	std::vector<VariableDeclaration const*> const& getLocalVariables() const { return m_localVariables; }
+
+private:
+	std::vector<VariableDeclaration const*> m_localVariables;
+};
+
+/**
+ * Abstract class that is added to each AST node that can receive documentation.
+ */
+class Documented
+{
+public:
+	explicit Documented(ASTPointer<ASTString> const& _documentation): m_documentation(_documentation) {}
+
+	/// @return A shared pointer of an ASTString.
+	/// Can contain a nullptr in which case indicates absence of documentation
+	ASTPointer<ASTString> const& getDocumentation() const { return m_documentation; }
+
+protected:
+	ASTPointer<ASTString> m_documentation;
+};
+
+/// @}
+
 /**
  * Definition of a contract. This is the only AST nodes where child nodes are not visited in
  * document order. It first visits all struct declarations, then all variable declarations and
diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index 33a71bca0..79672ca10 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -160,7 +160,7 @@ void Compiler::appendFunctionSelector(ContractDefinition const& _contract)
 
 	for (auto const& it: interfaceFunctions)
 	{
-		FunctionTypePointer functionType = it.second;
+		FunctionTypePointer const& functionType = it.second;
 		m_context << callDataUnpackerEntryPoints.at(it.first);
 		eth::AssemblyItem returnTag = m_context.pushNewTag();
 		appendCalldataUnpacker(functionType->getParameterTypes());
diff --git a/libsolidity/InterfaceHandler.cpp b/libsolidity/InterfaceHandler.cpp
index dd569946a..4d3ec4d50 100644
--- a/libsolidity/InterfaceHandler.cpp
+++ b/libsolidity/InterfaceHandler.cpp
@@ -60,6 +60,7 @@ std::unique_ptr<std::string> InterfaceHandler::getABIInterface(ContractDefinitio
 			return params;
 		};
 
+		solAssert(it.second->getDeclaration(), "All function interface types should contain a declaration");
 		method["name"] = it.second->getDeclaration()->getName();
 		method["constant"] = it.second->isConstant();
 		method["inputs"] = populateParameters(it.second->getParameterNames(),
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index e7765e1b7..38caaf8ff 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -591,7 +591,7 @@ u256 StructType::getStorageOffsetOfMember(string const& _name) const
 FunctionType::FunctionType(FunctionDefinition const& _function, bool _isInternal):
 	m_location(_isInternal ? Location::INTERNAL : Location::EXTERNAL),
 	m_isConstant(_function.isDeclaredConst()),
-    m_declaration(&_function)
+	m_declaration(&_function)
 {
 	TypePointers params;
 	vector<string> paramNames;
@@ -641,6 +641,9 @@ bool FunctionType::operator==(Type const& _other) const
 
 	if (m_location != other.m_location)
 		return false;
+	if (m_isConstant != other.isConstant())
+		return false;
+
 	if (m_parameterTypes.size() != other.m_parameterTypes.size() ||
 			m_returnParameterTypes.size() != other.m_returnParameterTypes.size())
 		return false;
@@ -763,7 +766,7 @@ vector<string> const FunctionType::getReturnParameterTypeNames() const
 
 ASTPointer<ASTString> FunctionType::getDocumentation() const
 {
-	auto function = dynamic_cast<FunctionDefinition const*>(m_declaration);
+	auto function = dynamic_cast<Documented const*>(m_declaration);
 	if (function)
 		return function->getDocumentation();