diff --git a/libsolidity/analysis/NameAndTypeResolver.cpp b/libsolidity/analysis/NameAndTypeResolver.cpp
index 2791fed7e..5fea91d6e 100644
--- a/libsolidity/analysis/NameAndTypeResolver.cpp
+++ b/libsolidity/analysis/NameAndTypeResolver.cpp
@@ -44,18 +44,12 @@ NameAndTypeResolver::NameAndTypeResolver(
 		m_scopes[nullptr]->registerDeclaration(*declaration);
 }
 
-bool NameAndTypeResolver::registerDeclarations(SourceUnit& _sourceUnit)
+bool NameAndTypeResolver::registerDeclarations(ASTNode& _sourceUnit)
 {
-	if (!m_scopes[&_sourceUnit])
-		// By importing, it is possible that the container already exists.
-		m_scopes[&_sourceUnit].reset(new DeclarationContainer(nullptr, m_scopes[nullptr].get()));
-	m_currentScope = m_scopes[&_sourceUnit].get();
-
 	// The helper registers all declarations in m_scopes as a side-effect of its construction.
 	try
 	{
 		DeclarationRegistrationHelper registrar(m_scopes, _sourceUnit, m_errors);
-		_sourceUnit.annotation().exportedSymbols = m_scopes[&_sourceUnit]->declarations();
 	}
 	catch (FatalError const&)
 	{
@@ -458,11 +452,26 @@ DeclarationRegistrationHelper::DeclarationRegistrationHelper(
 	ErrorList& _errors
 ):
 	m_scopes(_scopes),
-	m_currentScope(&_astRoot),
+	m_currentScope(nullptr),
 	m_errors(_errors)
 {
-	solAssert(!!m_scopes.at(m_currentScope), "");
 	_astRoot.accept(*this);
+	solAssert(m_currentScope == nullptr, "Scopes not correctly closed.");
+}
+
+bool DeclarationRegistrationHelper::visit(SourceUnit& _sourceUnit)
+{
+	if (!m_scopes[&_sourceUnit])
+		// By importing, it is possible that the container already exists.
+		m_scopes[&_sourceUnit].reset(new DeclarationContainer(nullptr, m_scopes[nullptr].get()));
+	m_currentScope = &_sourceUnit;
+	return true;
+}
+
+void DeclarationRegistrationHelper::endVisit(SourceUnit& _sourceUnit)
+{
+	_sourceUnit.annotation().exportedSymbols = m_scopes[&_sourceUnit]->declarations();
+	closeCurrentScope();
 }
 
 bool DeclarationRegistrationHelper::visit(ImportDirective& _import)
@@ -583,12 +592,13 @@ void DeclarationRegistrationHelper::enterNewSubScope(Declaration const& _declara
 
 void DeclarationRegistrationHelper::closeCurrentScope()
 {
-	solAssert(m_currentScope, "Closed non-existing scope.");
+	solAssert(m_currentScope && m_scopes.count(m_currentScope), "Closed non-existing scope.");
 	m_currentScope = m_scopes[m_currentScope]->enclosingNode();
 }
 
 void DeclarationRegistrationHelper::registerDeclaration(Declaration& _declaration, bool _opensScope)
 {
+	solAssert(m_currentScope && m_scopes.count(m_currentScope), "No current scope.");
 	if (!m_scopes[m_currentScope]->registerDeclaration(_declaration, nullptr, !_declaration.isVisibleInContract()))
 	{
 		SourceLocation firstDeclarationLocation;
diff --git a/libsolidity/analysis/NameAndTypeResolver.h b/libsolidity/analysis/NameAndTypeResolver.h
index fb018d749..67a6c0e4b 100644
--- a/libsolidity/analysis/NameAndTypeResolver.h
+++ b/libsolidity/analysis/NameAndTypeResolver.h
@@ -43,9 +43,9 @@ class NameAndTypeResolver: private boost::noncopyable
 {
 public:
 	NameAndTypeResolver(std::vector<Declaration const*> const& _globals, ErrorList& _errors);
-	/// Registers all declarations found in the source unit.
+	/// Registers all declarations found in the AST node, usually a source unit.
 	/// @returns false in case of error.
-	bool registerDeclarations(SourceUnit& _sourceUnit);
+	bool registerDeclarations(ASTNode& _sourceUnit);
 	/// Applies the effect of import directives.
 	bool performImports(SourceUnit& _sourceUnit, std::map<std::string, SourceUnit const*> const& _sourceUnits);
 	/// Resolves all names and types referenced from the given AST Node.
@@ -133,6 +133,8 @@ public:
 	);
 
 private:
+	bool visit(SourceUnit& _sourceUnit) override;
+	void endVisit(SourceUnit& _sourceUnit) override;
 	bool visit(ImportDirective& _declaration) override;
 	bool visit(ContractDefinition& _contract) override;
 	void endVisit(ContractDefinition& _contract) override;
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 533c787b7..be59d3d26 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -32,11 +32,11 @@ using namespace dev;
 using namespace dev::solidity;
 
 
-bool TypeChecker::checkTypeRequirements(ContractDefinition const& _contract)
+bool TypeChecker::checkTypeRequirements(ASTNode const& _contract)
 {
 	try
 	{
-		visit(_contract);
+		_contract.accept(*this);
 	}
 	catch (FatalError const&)
 	{
diff --git a/libsolidity/analysis/TypeChecker.h b/libsolidity/analysis/TypeChecker.h
index 143b15b26..46d8230ab 100644
--- a/libsolidity/analysis/TypeChecker.h
+++ b/libsolidity/analysis/TypeChecker.h
@@ -47,7 +47,7 @@ public:
 
 	/// Performs type checking on the given contract and all of its sub-nodes.
 	/// @returns true iff all checks passed. Note even if all checks passed, errors() can still contain warnings
-	bool checkTypeRequirements(ContractDefinition const& _contract);
+	bool checkTypeRequirements(ASTNode const& _contract);
 
 	/// @returns the type of an expression and asserts that it is present.
 	TypePointer const& type(Expression const& _expression) const;