Refactoring: Check types outside of AST and recover from some errors.

29 files changed, 2035 insertions, 1587 deletions

diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index daa84016..4cd6cc0f 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -22,7 +22,6 @@
 
 #include <algorithm>
 #include <functional>
-#include <boost/range/adaptor/reversed.hpp>
 #include <libsolidity/Utils.h>
 #include <libsolidity/AST.h>
 #include <libsolidity/ASTVisitor.h>
@@ -32,83 +31,21 @@
 #include <libdevcore/SHA3.h>
 
 using namespace std;
+using namespace dev;
+using namespace dev::solidity;
 
-namespace dev
+ASTNode::ASTNode(SourceLocation const& _location):
+	m_location(_location)
 {
-namespace solidity
-{
-
-TypeError ASTNode::createTypeError(string const& _description) const
-{
-	return TypeError() << errinfo_sourceLocation(location()) << errinfo_comment(_description);
 }
 
-TypePointer ContractDefinition::type(ContractDefinition const* _currentContract) const
+ASTNode::~ASTNode()
 {
-	return make_shared<TypeType>(make_shared<ContractType>(*this), _currentContract);
 }
 
-void ContractDefinition::checkTypeRequirements()
+TypeError ASTNode::createTypeError(string const& _description) const
 {
-	for (ASTPointer<InheritanceSpecifier> const& baseSpecifier: baseContracts())
-		baseSpecifier->checkTypeRequirements();
-
-	checkDuplicateFunctions();
-	checkIllegalOverrides();
-	checkAbstractFunctions();
-	checkAbstractConstructors();
-
-	FunctionDefinition const* functionDefinition = constructor();
-	if (functionDefinition && !functionDefinition->returnParameters().empty())
-		BOOST_THROW_EXCEPTION(functionDefinition->returnParameterList()->createTypeError(
-			"Non-empty \"returns\" directive for constructor."
-		));
-
-	FunctionDefinition const* fallbackFunction = nullptr;
-	for (ASTPointer<FunctionDefinition> const& function: definedFunctions())
-	{
-		if (function->name().empty())
-		{
-			if (fallbackFunction)
-				BOOST_THROW_EXCEPTION(DeclarationError() << errinfo_comment("Only one fallback function is allowed."));
-			else
-			{
-				fallbackFunction = function.get();
-				if (!fallbackFunction->parameters().empty())
-					BOOST_THROW_EXCEPTION(fallbackFunction->parameterList().createTypeError("Fallback function cannot take parameters."));
-			}
-		}
-		if (!function->isFullyImplemented())
-			setFullyImplemented(false);
-	}
-
-	for (ASTPointer<VariableDeclaration> const& variable: m_stateVariables)
-		variable->checkTypeRequirements();
-
-	for (ASTPointer<EventDefinition> const& event: events())
-		event->checkTypeRequirements();
-
-	for (ASTPointer<ModifierDefinition> const& modifier: functionModifiers())
-		modifier->checkTypeRequirements();
-
-	for (ASTPointer<FunctionDefinition> const& function: definedFunctions())
-		function->checkTypeRequirements();
-
-	checkExternalTypeClashes();
-	// check for hash collisions in function signatures
-	set<FixedHash<4>> hashes;
-	for (auto const& it: interfaceFunctionList())
-	{
-		FixedHash<4> const& hash = it.first;
-		if (hashes.count(hash))
-			BOOST_THROW_EXCEPTION(createTypeError(
-				string("Function signature hash collision for ") + it.second->externalSignature()
-			));
-		hashes.insert(hash);
-	}
-
-	if (isLibrary())
-		checkLibraryRequirements();
+	return TypeError() << errinfo_sourceLocation(location()) << errinfo_comment(_description);
 }
 
 map<FixedHash<4>, FunctionTypePointer> ContractDefinition::interfaceFunctions() const
@@ -137,227 +74,20 @@ FunctionDefinition const* ContractDefinition::constructor() const
 
 FunctionDefinition const* ContractDefinition::fallbackFunction() const
 {
-	for (ContractDefinition const* contract: linearizedBaseContracts())
+	for (ContractDefinition const* contract: annotation().linearizedBaseContracts)
 		for (ASTPointer<FunctionDefinition> const& f: contract->definedFunctions())
 			if (f->name().empty())
 				return f.get();
 	return nullptr;
 }
 
-void ContractDefinition::checkDuplicateFunctions() const
-{
-	/// Checks that two functions with the same name defined in this contract have different
-	/// argument types and that there is at most one constructor.
-	map<string, vector<FunctionDefinition const*>> functions;
-	for (ASTPointer<FunctionDefinition> const& function: definedFunctions())
-		functions[function->name()].push_back(function.get());
-
-	if (functions[name()].size() > 1)
-	{
-		SecondarySourceLocation ssl;
-		auto it = functions[name()].begin();
-		++it;
-		for (; it != functions[name()].end(); ++it)
-			ssl.append("Another declaration is here:", (*it)->location());
-
-		BOOST_THROW_EXCEPTION(
-			DeclarationError() <<
-			errinfo_sourceLocation(functions[name()].front()->location()) <<
-			errinfo_comment("More than one constructor defined.") <<
-			errinfo_secondarySourceLocation(ssl)
-		);
-	}
-	for (auto const& it: functions)
-	{
-		vector<FunctionDefinition const*> const& overloads = it.second;
-		for (size_t i = 0; i < overloads.size(); ++i)
-			for (size_t j = i + 1; j < overloads.size(); ++j)
-				if (FunctionType(*overloads[i]).hasEqualArgumentTypes(FunctionType(*overloads[j])))
-					BOOST_THROW_EXCEPTION(
-						DeclarationError() <<
-						errinfo_sourceLocation(overloads[j]->location()) <<
-						errinfo_comment("Function with same name and arguments defined twice.") <<
-						errinfo_secondarySourceLocation(SecondarySourceLocation().append(
-							"Other declaration is here:", overloads[i]->location())
-						)
-
-					);
-	}
-}
-
-void ContractDefinition::checkAbstractFunctions()
-{
-	// Mapping from name to function definition (exactly one per argument type equality class) and
-	// flag to indicate whether it is fully implemented.
-	using FunTypeAndFlag = std::pair<FunctionTypePointer, bool>;
-	map<string, vector<FunTypeAndFlag>> functions;
-
-	// Search from base to derived
-	for (ContractDefinition const* contract: boost::adaptors::reverse(linearizedBaseContracts()))
-		for (ASTPointer<FunctionDefinition> const& function: contract->definedFunctions())
-		{
-			auto& overloads = functions[function->name()];
-			FunctionTypePointer funType = make_shared<FunctionType>(*function);
-			auto it = find_if(overloads.begin(), overloads.end(), [&](FunTypeAndFlag const& _funAndFlag)
-			{
-				return funType->hasEqualArgumentTypes(*_funAndFlag.first);
-			});
-			if (it == overloads.end())
-				overloads.push_back(make_pair(funType, function->isFullyImplemented()));
-			else if (it->second)
-			{
-				if (!function->isFullyImplemented())
-					BOOST_THROW_EXCEPTION(function->createTypeError("Redeclaring an already implemented function as abstract"));
-			}
-			else if (function->isFullyImplemented())
-				it->second = true;
-		}
-
-	// Set to not fully implemented if at least one flag is false.
-	for (auto const& it: functions)
-		for (auto const& funAndFlag: it.second)
-			if (!funAndFlag.second)
-			{
-				setFullyImplemented(false);
-				return;
-			}
-}
-
-void ContractDefinition::checkAbstractConstructors()
-{
-	set<ContractDefinition const*> argumentsNeeded;
-	// check that we get arguments for all base constructors that need it.
-	// If not mark the contract as abstract (not fully implemented)
-
-	vector<ContractDefinition const*> const& bases = linearizedBaseContracts();
-	for (ContractDefinition const* contract: bases)
-		if (FunctionDefinition const* constructor = contract->constructor())
-			if (contract != this && !constructor->parameters().empty())
-				argumentsNeeded.insert(contract);
-
-	for (ContractDefinition const* contract: bases)
-	{
-		if (FunctionDefinition const* constructor = contract->constructor())
-			for (auto const& modifier: constructor->modifiers())
-			{
-				auto baseContract = dynamic_cast<ContractDefinition const*>(
-					&modifier->name()->referencedDeclaration()
-				);
-				if (baseContract)
-					argumentsNeeded.erase(baseContract);
-			}
-
-
-		for (ASTPointer<InheritanceSpecifier> const& base: contract->baseContracts())
-		{
-			auto baseContract = dynamic_cast<ContractDefinition const*>(
-				&base->name()->referencedDeclaration()
-			);
-			solAssert(baseContract, "");
-			if (!base->arguments().empty())
-				argumentsNeeded.erase(baseContract);
-		}
-	}
-	if (!argumentsNeeded.empty())
-		setFullyImplemented(false);
-}
-
-void ContractDefinition::checkIllegalOverrides() const
-{
-	// TODO unify this at a later point. for this we need to put the constness and the access specifier
-	// into the types
-	map<string, vector<FunctionDefinition const*>> functions;
-	map<string, ModifierDefinition const*> modifiers;
-
-	// We search from derived to base, so the stored item causes the error.
-	for (ContractDefinition const* contract: linearizedBaseContracts())
-	{
-		for (ASTPointer<FunctionDefinition> const& function: contract->definedFunctions())
-		{
-			if (function->isConstructor())
-				continue; // constructors can neither be overridden nor override anything
-			string const& name = function->name();
-			if (modifiers.count(name))
-				BOOST_THROW_EXCEPTION(modifiers[name]->createTypeError("Override changes function to modifier."));
-			FunctionType functionType(*function);
-			// function should not change the return type
-			for (FunctionDefinition const* overriding: functions[name])
-			{
-				FunctionType overridingType(*overriding);
-				if (!overridingType.hasEqualArgumentTypes(functionType))
-					continue;
-				if (
-					overriding->visibility() != function->visibility() ||
-					overriding->isDeclaredConst() != function->isDeclaredConst() ||
-					overridingType != functionType
-				)
-					BOOST_THROW_EXCEPTION(overriding->createTypeError("Override changes extended function signature."));
-			}
-			functions[name].push_back(function.get());
-		}
-		for (ASTPointer<ModifierDefinition> const& modifier: contract->functionModifiers())
-		{
-			string const& name = modifier->name();
-			ModifierDefinition const*& override = modifiers[name];
-			if (!override)
-				override = modifier.get();
-			else if (ModifierType(*override) != ModifierType(*modifier))
-				BOOST_THROW_EXCEPTION(override->createTypeError("Override changes modifier signature."));
-			if (!functions[name].empty())
-				BOOST_THROW_EXCEPTION(override->createTypeError("Override changes modifier to function."));
-		}
-	}
-}
-
-void ContractDefinition::checkExternalTypeClashes() const
-{
-	map<string, vector<pair<Declaration const*, shared_ptr<FunctionType>>>> externalDeclarations;
-	for (ContractDefinition const* contract: linearizedBaseContracts())
-	{
-		for (ASTPointer<FunctionDefinition> const& f: contract->definedFunctions())
-			if (f->isPartOfExternalInterface())
-			{
-				auto functionType = make_shared<FunctionType>(*f);
-				externalDeclarations[functionType->externalSignature(f->name())].push_back(
-					make_pair(f.get(), functionType)
-				);
-			}
-		for (ASTPointer<VariableDeclaration> const& v: contract->stateVariables())
-			if (v->isPartOfExternalInterface())
-			{
-				auto functionType = make_shared<FunctionType>(*v);
-				externalDeclarations[functionType->externalSignature(v->name())].push_back(
-					make_pair(v.get(), functionType)
-				);
-			}
-	}
-	for (auto const& it: externalDeclarations)
-		for (size_t i = 0; i < it.second.size(); ++i)
-			for (size_t j = i + 1; j < it.second.size(); ++j)
-				if (!it.second[i].second->hasEqualArgumentTypes(*it.second[j].second))
-					BOOST_THROW_EXCEPTION(it.second[j].first->createTypeError(
-						"Function overload clash during conversion to external types for arguments."
-					));
-}
-
-void ContractDefinition::checkLibraryRequirements() const
-{
-	solAssert(m_isLibrary, "");
-	if (!m_baseContracts.empty())
-		BOOST_THROW_EXCEPTION(createTypeError("Library is not allowed to inherit."));
-
-	for (auto const& var: m_stateVariables)
-		if (!var->isConstant())
-			BOOST_THROW_EXCEPTION(var->createTypeError("Library cannot have non-constant state variables"));
-}
-
 vector<ASTPointer<EventDefinition>> const& ContractDefinition::interfaceEvents() const
 {
 	if (!m_interfaceEvents)
 	{
 		set<string> eventsSeen;
 		m_interfaceEvents.reset(new vector<ASTPointer<EventDefinition>>());
-		for (ContractDefinition const* contract: linearizedBaseContracts())
+		for (ContractDefinition const* contract: annotation().linearizedBaseContracts)
 			for (ASTPointer<EventDefinition> const& e: contract->events())
 				if (eventsSeen.count(e->name()) == 0)
 				{
@@ -375,7 +105,7 @@ vector<pair<FixedHash<4>, FunctionTypePointer>> const& ContractDefinition::inter
 		set<string> functionsSeen;
 		set<string> signaturesSeen;
 		m_interfaceFunctionList.reset(new vector<pair<FixedHash<4>, FunctionTypePointer>>());
-		for (ContractDefinition const* contract: linearizedBaseContracts())
+		for (ContractDefinition const* contract: annotation().linearizedBaseContracts)
 		{
 			for (ASTPointer<FunctionDefinition> const& f: contract->definedFunctions())
 			{
@@ -395,7 +125,7 @@ vector<pair<FixedHash<4>, FunctionTypePointer>> const& ContractDefinition::inter
 				if (functionsSeen.count(v->name()) == 0 && v->isPartOfExternalInterface())
 				{
 					FunctionType ftype(*v);
-					solAssert(v->type().get(), "");
+					solAssert(!!v->annotation().type.get(), "");
 					functionsSeen.insert(v->name());
 					FixedHash<4> hash(dev::sha3(ftype.externalSignature(v->name())));
 					m_interfaceFunctionList->push_back(make_pair(hash, make_shared<FunctionType>(*v)));
@@ -453,45 +183,9 @@ vector<Declaration const*> const& ContractDefinition::inheritableMembers() const
 	return *m_inheritableMembers;
 }
 
-TypePointer EnumValue::type(ContractDefinition const*) const
+TypePointer ContractDefinition::type(ContractDefinition const* m_currentContract) const
 {
-	EnumDefinition const* parentDef = dynamic_cast<EnumDefinition const*>(scope());
-	solAssert(parentDef, "Enclosing Scope of EnumValue was not set");
-	return make_shared<EnumType>(*parentDef);
-}
-
-void InheritanceSpecifier::checkTypeRequirements()
-{
-	m_baseName->checkTypeRequirements(nullptr);
-	for (ASTPointer<Expression> const& argument: m_arguments)
-		argument->checkTypeRequirements(nullptr);
-
-	ContractDefinition const* base = dynamic_cast<ContractDefinition const*>(&m_baseName->referencedDeclaration());
-	solAssert(base, "Base contract not available.");
-
-	if (base->isLibrary())
-		BOOST_THROW_EXCEPTION(createTypeError("Libraries cannot be inherited from."));
-
-	TypePointers parameterTypes = ContractType(*base).constructorType()->parameterTypes();
-	if (!m_arguments.empty() && parameterTypes.size() != m_arguments.size())
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Wrong argument count for constructor call: " +
-			toString(m_arguments.size()) +
-			" arguments given but expected " +
-			toString(parameterTypes.size()) +
-			"."
-		));
-
-	for (size_t i = 0; i < m_arguments.size(); ++i)
-		if (!m_arguments[i]->type()->isImplicitlyConvertibleTo(*parameterTypes[i]))
-			BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError(
-				"Invalid type for argument in constructor call. "
-				"Invalid implicit conversion from " +
-				m_arguments[i]->type()->toString() +
-				" to " +
-				parameterTypes[i]->toString() +
-				" requested."
-			));
+	return make_shared<TypeType>(make_shared<ContractType>(*this), m_currentContract);
 }
 
 TypePointer StructDefinition::type(ContractDefinition const*) const
@@ -499,38 +193,11 @@ TypePointer StructDefinition::type(ContractDefinition const*) const
 	return make_shared<TypeType>(make_shared<StructType>(*this));
 }
 
-void StructDefinition::checkMemberTypes() const
-{
-	for (ASTPointer<VariableDeclaration> const& member: members())
-		if (!member->type()->canBeStored())
-			BOOST_THROW_EXCEPTION(member->createTypeError("Type cannot be used in struct."));
-}
-
-void StructDefinition::checkRecursion() const
+TypePointer EnumValue::type(ContractDefinition const*) const
 {
-	using StructPointer = StructDefinition const*;
-	using StructPointersSet = set<StructPointer>;
-	function<void(StructPointer,StructPointersSet const&)> check = [&](StructPointer _struct, StructPointersSet const& _parents)
-	{
-		if (_parents.count(_struct))
-			BOOST_THROW_EXCEPTION(
-				ParserError() <<
-				errinfo_sourceLocation(_struct->location()) <<
-				errinfo_comment("Recursive struct definition.")
-			);
-		set<StructDefinition const*> parents = _parents;
-		parents.insert(_struct);
-		for (ASTPointer<VariableDeclaration> const& member: _struct->members())
-			if (member->type()->category() == Type::Category::Struct)
-			{
-				auto const& typeName = dynamic_cast<UserDefinedTypeName const&>(*member->typeName());
-				check(
-					&dynamic_cast<StructDefinition const&>(*typeName.referencedDeclaration()),
-					parents
-				);
-			}
-	};
-	check(this, StructPointersSet{});
+	auto parentDef = dynamic_cast<EnumDefinition const*>(scope());
+	solAssert(parentDef, "Enclosing Scope of EnumValue was not set");
+	return make_shared<EnumType>(*parentDef);
 }
 
 TypePointer EnumDefinition::type(ContractDefinition const*) const
@@ -543,92 +210,25 @@ TypePointer FunctionDefinition::type(ContractDefinition const*) const
 	return make_shared<FunctionType>(*this);
 }
 
-void FunctionDefinition::checkTypeRequirements()
-{
-	for (ASTPointer<VariableDeclaration> const& var: parameters() + returnParameters())
-	{
-		if (!var->type()->canLiveOutsideStorage())
-			BOOST_THROW_EXCEPTION(var->createTypeError("Type is required to live outside storage."));
-		if (visibility() >= Visibility::Public && !(var->type()->externalType()))
-			BOOST_THROW_EXCEPTION(var->createTypeError("Internal type is not allowed for public and external functions."));
-	}
-	for (ASTPointer<ModifierInvocation> const& modifier: m_functionModifiers)
-		modifier->checkTypeRequirements(isConstructor() ?
-			dynamic_cast<ContractDefinition const&>(*scope()).linearizedBaseContracts() :
-			vector<ContractDefinition const*>());
-	if (m_body)
-		m_body->checkTypeRequirements();
-}
-
 string FunctionDefinition::externalSignature() const
 {
 	return FunctionType(*this).externalSignature(name());
 }
 
-bool VariableDeclaration::isLValue() const
+TypePointer ModifierDefinition::type(ContractDefinition const*) const
 {
-	// External function parameters and constant declared variables are Read-Only
-	return !isExternalCallableParameter() && !m_isConstant;
+	return make_shared<ModifierType>(*this);
 }
 
-void VariableDeclaration::checkTypeRequirements()
+TypePointer EventDefinition::type(ContractDefinition const*) const
 {
-	// Variables can be declared without type (with "var"), in which case the first assignment
-	// sets the type.
-	// Note that assignments before the first declaration are legal because of the special scoping
-	// rules inherited from JavaScript.
-	if (m_isConstant)
-	{
-		if (!dynamic_cast<ContractDefinition const*>(scope()))
-			BOOST_THROW_EXCEPTION(createTypeError("Illegal use of \"constant\" specifier."));
-		if (!m_value)
-			BOOST_THROW_EXCEPTION(createTypeError("Uninitialized \"constant\" variable."));
-		if (m_type && !m_type->isValueType())
-		{
-			// TODO: const is implemented only for uint, bytesXX, string and enums types.
-			bool constImplemented = false;
-			if (auto arrayType = dynamic_cast<ArrayType const*>(m_type.get()))
-				constImplemented = arrayType->isByteArray();
-			if (!constImplemented)
-				BOOST_THROW_EXCEPTION(createTypeError(
-					"Illegal use of \"constant\" specifier. \"constant\" "
-					"is not yet implemented for this type."
-				));
-		}
-	}
-	if (m_type)
-	{
-		if (m_value)
-			m_value->expectType(*m_type);
-	}
-	else
-	{
-		if (!m_value)
-			// This feature might be extended in the future.
-			BOOST_THROW_EXCEPTION(createTypeError("Assignment necessary for type detection."));
-		m_value->checkTypeRequirements(nullptr);
+	return make_shared<FunctionType>(*this);
+}
 
-		TypePointer const& type = m_value->type();
-		if (
-			type->category() == Type::Category::IntegerConstant &&
-			!dynamic_pointer_cast<IntegerConstantType const>(type)->integerType()
-		)
-			BOOST_THROW_EXCEPTION(m_value->createTypeError("Invalid integer constant " + type->toString() + "."));
-		else if (type->category() == Type::Category::Void)
-			BOOST_THROW_EXCEPTION(createTypeError("Variable cannot have void type."));
-		m_type = type->mobileType();
-	}
-	solAssert(!!m_type, "");
-	if (!m_isStateVariable)
-	{
-		if (m_type->dataStoredIn(DataLocation::Memory) || m_type->dataStoredIn(DataLocation::CallData))
-			if (!m_type->canLiveOutsideStorage())
-				BOOST_THROW_EXCEPTION(createTypeError(
-					"Type " + m_type->toString() + " is only valid in storage."
-				));
-	}
-	else if (visibility() >= Visibility::Public && !FunctionType(*this).externalType())
-		BOOST_THROW_EXCEPTION(createTypeError("Internal type is not allowed for public state variables."));
+bool VariableDeclaration::isLValue() const
+{
+	// External function parameters and constant declared variables are Read-Only
+	return !isExternalCallableParameter() && !m_isConstant;
 }
 
 bool VariableDeclaration::isCallableParameter() const
@@ -657,578 +257,13 @@ bool VariableDeclaration::isExternalCallableParameter() const
 	return false;
 }
 
-TypePointer ModifierDefinition::type(ContractDefinition const*) const
+bool VariableDeclaration::canHaveAutoType() const
 {
-	return make_shared<ModifierType>(*this);
-}
-
-void ModifierDefinition::checkTypeRequirements()
-{
-	m_body->checkTypeRequirements();
-}
-
-void ModifierInvocation::checkTypeRequirements(vector<ContractDefinition const*> const& _bases)
-{
-	TypePointers argumentTypes;
-	for (ASTPointer<Expression> const& argument: m_arguments)
-	{
-		argument->checkTypeRequirements(nullptr);
-		argumentTypes.push_back(argument->type());
-	}
-	m_modifierName->checkTypeRequirements(&argumentTypes);
-
-	auto const* declaration = &m_modifierName->referencedDeclaration();
-	vector<ASTPointer<VariableDeclaration>> emptyParameterList;
-	vector<ASTPointer<VariableDeclaration>> const* parameters = nullptr;
-	if (auto modifier = dynamic_cast<ModifierDefinition const*>(declaration))
-		parameters = &modifier->parameters();
-	else
-		// check parameters for Base constructors
-		for (ContractDefinition const* base: _bases)
-			if (declaration == base)
-			{
-				if (auto referencedConstructor = base->constructor())
-					parameters = &referencedConstructor->parameters();
-				else
-					parameters = &emptyParameterList;
-				break;
-			}
-	if (!parameters)
-		BOOST_THROW_EXCEPTION(createTypeError("Referenced declaration is neither modifier nor base class."));
-	if (parameters->size() != m_arguments.size())
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Wrong argument count for modifier invocation: " +
-			toString(m_arguments.size()) +
-			" arguments given but expected " +
-			toString(parameters->size()) +
-			"."
-		));
-	for (size_t i = 0; i < m_arguments.size(); ++i)
-		if (!m_arguments[i]->type()->isImplicitlyConvertibleTo(*(*parameters)[i]->type()))
-			BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError(
-				"Invalid type for argument in modifier invocation. "
-				"Invalid implicit conversion from " +
-				m_arguments[i]->type()->toString() +
-				" to " +
-				(*parameters)[i]->type()->toString() +
-				" requested."
-			));
-}
-
-void EventDefinition::checkTypeRequirements()
-{
-	int numIndexed = 0;
-	for (ASTPointer<VariableDeclaration> const& var: parameters())
-	{
-		if (var->isIndexed())
-			numIndexed++;
-		if (numIndexed > 3)
-			BOOST_THROW_EXCEPTION(createTypeError("More than 3 indexed arguments for event."));
-		if (!var->type()->canLiveOutsideStorage())
-			BOOST_THROW_EXCEPTION(var->createTypeError("Type is required to live outside storage."));
-		if (!var->type()->externalType())
-			BOOST_THROW_EXCEPTION(var->createTypeError("Internal type is not allowed as event parameter type."));
-	}
-}
-
-void Block::checkTypeRequirements()
-{
-	for (shared_ptr<Statement> const& statement: m_statements)
-		statement->checkTypeRequirements();
-}
-
-void IfStatement::checkTypeRequirements()
-{
-	m_condition->expectType(BoolType());
-	m_trueBody->checkTypeRequirements();
-	if (m_falseBody)
-		m_falseBody->checkTypeRequirements();
-}
-
-void WhileStatement::checkTypeRequirements()
-{
-	m_condition->expectType(BoolType());
-	m_body->checkTypeRequirements();
-}
-
-void ForStatement::checkTypeRequirements()
-{
-	if (m_initExpression)
-		m_initExpression->checkTypeRequirements();
-	if (m_condExpression)
-		m_condExpression->expectType(BoolType());
-	if (m_loopExpression)
-		m_loopExpression->checkTypeRequirements();
-	m_body->checkTypeRequirements();
-}
-
-void Return::checkTypeRequirements()
-{
-	if (!m_expression)
-		return;
-	if (!m_returnParameters)
-		BOOST_THROW_EXCEPTION(createTypeError("Return arguments not allowed."));
-	if (m_returnParameters->parameters().size() != 1)
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Different number of arguments in return statement "
-			"than in returns declaration."
-		));
-	// this could later be changed such that the paramaters type is an anonymous struct type,
-	// but for now, we only allow one return parameter
-	m_expression->expectType(*m_returnParameters->parameters().front()->type());
-}
-
-void VariableDeclarationStatement::checkTypeRequirements()
-{
-	m_variable->checkTypeRequirements();
-}
-
-void Assignment::checkTypeRequirements(TypePointers const*)
-{
-	m_leftHandSide->checkTypeRequirements(nullptr);
-	m_leftHandSide->requireLValue();
-	if (m_leftHandSide->type()->category() == Type::Category::Mapping)
-		BOOST_THROW_EXCEPTION(createTypeError("Mappings cannot be assigned to."));
-	m_type = m_leftHandSide->type();
-	if (m_assigmentOperator == Token::Assign)
-		m_rightHandSide->expectType(*m_type);
-	else
-	{
-		// compound assignment
-		m_rightHandSide->checkTypeRequirements(nullptr);
-		TypePointer resultType = m_type->binaryOperatorResult(Token::AssignmentToBinaryOp(m_assigmentOperator),
-															  m_rightHandSide->type());
-		if (!resultType || *resultType != *m_type)
-			BOOST_THROW_EXCEPTION(createTypeError(
-				"Operator " +
-				string(Token::toString(m_assigmentOperator)) +
-				" not compatible with types " +
-				m_type->toString() +
-				" and " +
-				m_rightHandSide->type()->toString()
-			));
-	}
-}
-
-void ExpressionStatement::checkTypeRequirements()
-{
-	m_expression->checkTypeRequirements(nullptr);
-	if (m_expression->type()->category() == Type::Category::IntegerConstant)
-		if (!dynamic_pointer_cast<IntegerConstantType const>(m_expression->type())->integerType())
-			BOOST_THROW_EXCEPTION(m_expression->createTypeError("Invalid integer constant."));
-}
-
-void Expression::expectType(Type const& _expectedType)
-{
-	checkTypeRequirements(nullptr);
-	Type const& currentType = *type();
-	if (!currentType.isImplicitlyConvertibleTo(_expectedType))
-		BOOST_THROW_EXCEPTION(
-			createTypeError(
-				"Type " +
-				currentType.toString() +
-				" is not implicitly convertible to expected type " +
-				_expectedType.toString() +
-				"."
-			)
-		);
-}
-
-void Expression::requireLValue()
-{
-	if (!isLValue())
-		BOOST_THROW_EXCEPTION(createTypeError("Expression has to be an lvalue."));
-	m_lvalueRequested = true;
-}
-
-void UnaryOperation::checkTypeRequirements(TypePointers const*)
-{
-	// Inc, Dec, Add, Sub, Not, BitNot, Delete
-	m_subExpression->checkTypeRequirements(nullptr);
-	if (m_operator == Token::Value::Inc || m_operator == Token::Value::Dec || m_operator == Token::Value::Delete)
-		m_subExpression->requireLValue();
-	m_type = m_subExpression->type()->unaryOperatorResult(m_operator);
-	if (!m_type)
-		BOOST_THROW_EXCEPTION(createTypeError("Unary operator not compatible with type."));
-}
-
-void BinaryOperation::checkTypeRequirements(TypePointers const*)
-{
-	m_left->checkTypeRequirements(nullptr);
-	m_right->checkTypeRequirements(nullptr);
-	m_commonType = m_left->type()->binaryOperatorResult(m_operator, m_right->type());
-	if (!m_commonType)
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Operator " + string(Token::toString(m_operator)) +
-			" not compatible with types " +
-			m_left->type()->toString() +
-			" and " +
-			m_right->type()->toString()
-		));
-	m_type = Token::isCompareOp(m_operator) ? make_shared<BoolType>() : m_commonType;
-}
-
-void FunctionCall::checkTypeRequirements(TypePointers const*)
-{
-	bool isPositionalCall = m_names.empty();
-
-	// we need to check arguments' type first as they will be forwarded to
-	// m_expression->checkTypeRequirements
-	TypePointers argumentTypes;
-	for (ASTPointer<Expression> const& argument: m_arguments)
-	{
-		argument->checkTypeRequirements(nullptr);
-		// only store them for positional calls
-		if (isPositionalCall)
-			argumentTypes.push_back(argument->type());
-	}
-
-	m_expression->checkTypeRequirements(isPositionalCall ? &argumentTypes : nullptr);
-
-	TypePointer const& expressionType = m_expression->type();
-	FunctionTypePointer functionType;
-	if (isTypeConversion())
-	{
-		TypeType const& type = dynamic_cast<TypeType const&>(*expressionType);
-		if (m_arguments.size() != 1)
-			BOOST_THROW_EXCEPTION(createTypeError("Exactly one argument expected for explicit type conversion."));
-		if (!isPositionalCall)
-			BOOST_THROW_EXCEPTION(createTypeError("Type conversion cannot allow named arguments."));
-		m_type = type.actualType();
-		auto argType = m_arguments.front()->type();
-		if (auto argRefType = dynamic_cast<ReferenceType const*>(argType.get()))
-			// do not change the data location when converting
-			// (data location cannot yet be specified for type conversions)
-			m_type = ReferenceType::copyForLocationIfReference(argRefType->location(), m_type);
-		if (!argType->isExplicitlyConvertibleTo(*m_type))
-			BOOST_THROW_EXCEPTION(createTypeError("Explicit type conversion not allowed."));
-
-		return;
-	}
-
-	/// For error message: Struct members that were removed during conversion to memory.
-	set<string> membersRemovedForStructConstructor;
-	if (isStructConstructorCall())
-	{
-		TypeType const& type = dynamic_cast<TypeType const&>(*expressionType);
-		auto const& structType = dynamic_cast<StructType const&>(*type.actualType());
-		functionType = structType.constructorType();
-		membersRemovedForStructConstructor = structType.membersMissingInMemory();
-	}
-	else
-		functionType = dynamic_pointer_cast<FunctionType const>(expressionType);
-
-	if (!functionType)
-		BOOST_THROW_EXCEPTION(createTypeError("Type is not callable."));
-
-	//@todo would be nice to create a struct type from the arguments
-	// and then ask if that is implicitly convertible to the struct represented by the
-	// function parameters
-	TypePointers const& parameterTypes = functionType->parameterTypes();
-	if (!functionType->takesArbitraryParameters() && parameterTypes.size() != m_arguments.size())
-	{
-		string msg =
-			"Wrong argument count for function call: " +
-			toString(m_arguments.size()) +
-			" arguments given but expected " +
-			toString(parameterTypes.size()) +
-			".";
-		// Extend error message in case we try to construct a struct with mapping member.
-		if (isStructConstructorCall() && !membersRemovedForStructConstructor.empty())
-		{
-			msg += " Members that have to be skipped in memory:";
-			for (auto const& member: membersRemovedForStructConstructor)
-				msg += " " + member;
-		}
-		BOOST_THROW_EXCEPTION(createTypeError(msg));
-	}
-
-	if (isPositionalCall)
-	{
-		// call by positional arguments
-		for (size_t i = 0; i < m_arguments.size(); ++i)
-			if (
-				!functionType->takesArbitraryParameters() &&
-				!m_arguments[i]->type()->isImplicitlyConvertibleTo(*parameterTypes[i])
-			)
-				BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError(
-					"Invalid type for argument in function call. "
-					"Invalid implicit conversion from " +
-					m_arguments[i]->type()->toString() +
-					" to " +
-					parameterTypes[i]->toString() +
-					" requested."
-				));
-	}
-	else
-	{
-		// call by named arguments
-		if (functionType->takesArbitraryParameters())
-			BOOST_THROW_EXCEPTION(createTypeError(
-				"Named arguments cannnot be used for functions that take arbitrary parameters."
-			));
-		auto const& parameterNames = functionType->parameterNames();
-		if (parameterNames.size() != m_names.size())
-			BOOST_THROW_EXCEPTION(createTypeError("Some argument names are missing."));
-
-		// check duplicate names
-		for (size_t i = 0; i < m_names.size(); i++)
-			for (size_t j = i + 1; j < m_names.size(); j++)
-				if (*m_names[i] == *m_names[j])
-					BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError("Duplicate named argument."));
-
-		for (size_t i = 0; i < m_names.size(); i++) {
-			bool found = false;
-			for (size_t j = 0; j < parameterNames.size(); j++) {
-				if (parameterNames[j] == *m_names[i]) {
-					// check type convertible
-					if (!m_arguments[i]->type()->isImplicitlyConvertibleTo(*parameterTypes[j]))
-						BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError(
-							"Invalid type for argument in function call. "
-							"Invalid implicit conversion from " +
-							m_arguments[i]->type()->toString() +
-							" to " +
-							parameterTypes[i]->toString() +
-							" requested."
-						));
-
-					found = true;
-					break;
-				}
-			}
-			if (!found)
-				BOOST_THROW_EXCEPTION(createTypeError("Named argument does not match function declaration."));
-		}
-	}
-
-	// @todo actually the return type should be an anonymous struct,
-	// but we change it to the type of the first return value until we have anonymous
-	// structs and tuples
-	if (functionType->returnParameterTypes().empty())
-		m_type = make_shared<VoidType>();
-	else
-		m_type = functionType->returnParameterTypes().front();
-}
-
-bool FunctionCall::isTypeConversion() const
-{
-	return m_expression->type()->category() == Type::Category::TypeType && !isStructConstructorCall();
-}
-
-bool FunctionCall::isStructConstructorCall() const
-{
-	if (auto const* type = dynamic_cast<TypeType const*>(m_expression->type().get()))
-		return type->actualType()->category() == Type::Category::Struct;
-	else
-		return false;
-}
-
-void NewExpression::checkTypeRequirements(TypePointers const*)
-{
-	m_contractName->checkTypeRequirements(nullptr);
-	m_contract = dynamic_cast<ContractDefinition const*>(&m_contractName->referencedDeclaration());
-
-	if (!m_contract)
-		BOOST_THROW_EXCEPTION(createTypeError("Identifier is not a contract."));
-	if (!m_contract->isFullyImplemented())
-		BOOST_THROW_EXCEPTION(createTypeError("Trying to create an instance of an abstract contract."));
-
-	auto scopeContract = m_contractName->contractScope();
-	auto bases = m_contract->linearizedBaseContracts();
-	if (find(bases.begin(), bases.end(), scopeContract) != bases.end())
-		BOOST_THROW_EXCEPTION(createTypeError("Circular reference for contract creation: cannot create instance of derived or same contract."));
-
-	shared_ptr<ContractType const> contractType = make_shared<ContractType>(*m_contract);
-	TypePointers const& parameterTypes = contractType->constructorType()->parameterTypes();
-	m_type = make_shared<FunctionType>(
-		parameterTypes,
-		TypePointers{contractType},
-		strings(),
-		strings(),
-		FunctionType::Location::Creation
-	);
-}
-
-void MemberAccess::checkTypeRequirements(TypePointers const* _argumentTypes)
-{
-	m_expression->checkTypeRequirements(nullptr);
-	Type const& type = *m_expression->type();
-
-	MemberList::MemberMap possibleMembers = type.members().membersByName(*m_memberName);
-	if (possibleMembers.size() > 1 && _argumentTypes)
-	{
-		// do override resolution
-		for (auto it = possibleMembers.begin(); it != possibleMembers.end();)
-			if (
-				it->type->category() == Type::Category::Function &&
-				!dynamic_cast<FunctionType const&>(*it->type).canTakeArguments(*_argumentTypes)
-			)
-				it = possibleMembers.erase(it);
-			else
-				++it;
-	}
-	if (possibleMembers.size() == 0)
-	{
-		auto storageType = ReferenceType::copyForLocationIfReference(
-			DataLocation::Storage,
-			m_expression->type()
-		);
-		if (!storageType->members().membersByName(*m_memberName).empty())
-			BOOST_THROW_EXCEPTION(createTypeError(
-				"Member \"" +
-				*m_memberName +
-				"\" is not available in " +
-				type.toString() +
-				" outside of storage."
-			));
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Member \"" +
-			*m_memberName +
-			"\" not found or not visible after argument-dependent lookup in " +
-			type.toString()
-		));
-	}
-	else if (possibleMembers.size() > 1)
-		BOOST_THROW_EXCEPTION(createTypeError(
-			"Member \"" +
-			*m_memberName +
-			"\" not unique after argument-dependent lookup in " +
-			type.toString()
-		));
-
-	m_referencedDeclaration = possibleMembers.front().declaration;
-	m_type = possibleMembers.front().type;
-	if (type.category() == Type::Category::Struct)
-		m_isLValue = true;
-	else if (type.category() == Type::Category::Array)
-	{
-		auto const& arrayType(dynamic_cast<ArrayType const&>(type));
-		m_isLValue = (
-			*m_memberName == "length" &&
-			arrayType.location() == DataLocation::Storage &&
-			arrayType.isDynamicallySized()
-		);
-	}
-	else
-		m_isLValue = false;
-}
-
-void IndexAccess::checkTypeRequirements(TypePointers const*)
-{
-	m_base->checkTypeRequirements(nullptr);
-	switch (m_base->type()->category())
-	{
-	case Type::Category::Array:
-	{
-		ArrayType const& type = dynamic_cast<ArrayType const&>(*m_base->type());
-		if (!m_index)
-			BOOST_THROW_EXCEPTION(createTypeError("Index expression cannot be omitted."));
-		if (type.isString())
-			BOOST_THROW_EXCEPTION(createTypeError("Index access for string is not possible."));
-		m_index->expectType(IntegerType(256));
-
-		m_type = type.baseType();
-		if (auto integerType = dynamic_cast<IntegerConstantType const*>(m_index->type().get()))
-			if (!type.isDynamicallySized() && type.length() <= integerType->literalValue(nullptr))
-				BOOST_THROW_EXCEPTION(createTypeError("Out of bounds access."));
-
-		m_isLValue = type.location() != DataLocation::CallData;
-		break;
-	}
-	case Type::Category::Mapping:
-	{
-		MappingType const& type = dynamic_cast<MappingType const&>(*m_base->type());
-		if (!m_index)
-			BOOST_THROW_EXCEPTION(createTypeError("Index expression cannot be omitted."));
-		m_index->expectType(*type.keyType());
-		m_type = type.valueType();
-		m_isLValue = true;
-		break;
-	}
-	case Type::Category::TypeType:
-	{
-		TypeType const& type = dynamic_cast<TypeType const&>(*m_base->type());
-		if (!m_index)
-			m_type = make_shared<TypeType>(make_shared<ArrayType>(DataLocation::Memory, type.actualType()));
-		else
-		{
-			m_index->checkTypeRequirements(nullptr);
-			auto length = dynamic_cast<IntegerConstantType const*>(m_index->type().get());
-			if (!length)
-				BOOST_THROW_EXCEPTION(m_index->createTypeError("Integer constant expected."));
-			m_type = make_shared<TypeType>(make_shared<ArrayType>(
-				DataLocation::Memory,
-				type.actualType(),
-				length->literalValue(nullptr)
-			));
-		}
-		break;
-	}
-	default:
-		BOOST_THROW_EXCEPTION(m_base->createTypeError(
-			"Indexed expression has to be a type, mapping or array (is " +
-			m_base->type()->toString() +
-			")"
-		));
-	}
-}
-
-void Identifier::checkTypeRequirements(TypePointers const* _argumentTypes)
-{
-	if (!m_referencedDeclaration)
-	{
-		if (!_argumentTypes)
-			BOOST_THROW_EXCEPTION(createTypeError("Unable to determine overloaded type."));
-		overloadResolution(*_argumentTypes);
-	}
-	solAssert(!!m_referencedDeclaration, "Referenced declaration is null after overload resolution.");
-	m_isLValue = m_referencedDeclaration->isLValue();
-	m_type = m_referencedDeclaration->type(m_contractScope);
-	if (!m_type)
-		BOOST_THROW_EXCEPTION(createTypeError("Declaration referenced before type could be determined."));
-}
-
-Declaration const& Identifier::referencedDeclaration() const
-{
-	solAssert(!!m_referencedDeclaration, "Identifier not resolved.");
-	return *m_referencedDeclaration;
-}
-
-void Identifier::overloadResolution(TypePointers const& _argumentTypes)
-{
-	solAssert(!m_referencedDeclaration, "Referenced declaration should be null before overload resolution.");
-	solAssert(!m_overloadedDeclarations.empty(), "No candidates for overload resolution found.");
-
-	vector<Declaration const*> possibles;
-	if (m_overloadedDeclarations.size() == 1)
-		m_referencedDeclaration = *m_overloadedDeclarations.begin();
-
-	for (Declaration const* declaration: m_overloadedDeclarations)
-	{
-		TypePointer const& function = declaration->type();
-		auto const* functionType = dynamic_cast<FunctionType const*>(function.get());
-		if (functionType && functionType->canTakeArguments(_argumentTypes))
-			possibles.push_back(declaration);
-	}
-	if (possibles.size() == 1)
-		m_referencedDeclaration = possibles.front();
-	else if (possibles.empty())
-		BOOST_THROW_EXCEPTION(createTypeError("No matching declaration found after argument-dependent lookup."));
-	else
-		BOOST_THROW_EXCEPTION(createTypeError("No unique declaration found after argument-dependent lookup."));
-}
-
-void ElementaryTypeNameExpression::checkTypeRequirements(TypePointers const*)
-{
-	m_type = make_shared<TypeType>(Type::fromElementaryTypeName(m_typeToken));
+	auto const* callable = dynamic_cast<CallableDeclaration const*>(scope());
+	return (!!callable && !isCallableParameter());
 }
 
-void Literal::checkTypeRequirements(TypePointers const*)
+TypePointer VariableDeclaration::type(ContractDefinition const*) const
 {
-	m_type = Type::forLiteral(*this);
-	if (!m_type)
-		BOOST_THROW_EXCEPTION(createTypeError("Invalid literal value."));
-}
-
-}
+	return annotation().type;
 }
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index de0ef3ef..08d26b70 100644
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -33,6 +33,7 @@
 #include <libsolidity/Token.h>
 #include <libsolidity/Types.h>
 #include <libsolidity/Exceptions.h>
+#include <libsolidity/ASTAnnotations.h>
 
 namespace dev
 {
@@ -41,6 +42,7 @@ namespace solidity
 
 class ASTVisitor;
 class ASTConstVisitor;
+struct ASTAnnotation;
 
 
 /**
@@ -51,9 +53,8 @@ class ASTConstVisitor;
 class ASTNode: private boost::noncopyable
 {
 public:
-	explicit ASTNode(SourceLocation const& _location): m_location(_location) {}
-
-	virtual ~ASTNode() {}
+	explicit ASTNode(SourceLocation const& _location);
+	virtual ~ASTNode();
 
 	virtual void accept(ASTVisitor& _visitor) = 0;
 	virtual void accept(ASTConstVisitor& _visitor) const = 0;
@@ -77,6 +78,9 @@ public:
 	/// the given description
 	TypeError createTypeError(std::string const& _description) const;
 
+	///@todo make this const-safe by providing a different way to access the annotation
+	ASTAnnotation& annotation() const { return const_cast<ASTAnnotation&>(m_annotation); }
+
 	///@{
 	///@name equality operators
 	/// Equality relies on the fact that nodes cannot be copied.
@@ -86,6 +90,8 @@ public:
 
 private:
 	SourceLocation m_location;
+
+	ASTAnnotation m_annotation;
 };
 
 /**
@@ -151,12 +157,14 @@ public:
 	Declaration const* scope() const { return m_scope; }
 	void setScope(Declaration const* _scope) { m_scope = _scope; }
 
+	virtual bool isLValue() const { return false; }
+	virtual bool isPartOfExternalInterface() const { return false; }
+
 	/// @returns the type of expressions referencing this declaration.
 	/// The current contract has to be given since this context can change the type, especially of
 	/// contract types.
+	/// This can only be called once types of variable declarations have already been resolved.
 	virtual TypePointer type(ContractDefinition const* m_currentContract = nullptr) const = 0;
-	virtual bool isLValue() const { return false; }
-	virtual bool isPartOfExternalInterface() const { return false; }
 
 protected:
 	virtual Visibility defaultVisibility() const { return Visibility::Public; }
@@ -205,8 +213,7 @@ public:
 	explicit ImplementationOptional(bool _implemented): m_implemented(_implemented) {}
 
 	/// @return whether this node is fully implemented or not
-	bool isFullyImplemented() const { return m_implemented; }
-	void setFullyImplemented(bool _implemented) {  m_implemented = _implemented; }
+	bool isImplemented() const { return m_implemented; }
 
 protected:
 	bool m_implemented;
@@ -219,7 +226,7 @@ protected:
  * document order. It first visits all struct declarations, then all variable declarations and
  * finally all function declarations.
  */
-class ContractDefinition: public Declaration, public Documented, public ImplementationOptional
+class ContractDefinition: public Declaration, public Documented
 {
 public:
 	ContractDefinition(
@@ -237,7 +244,6 @@ public:
 	):
 		Declaration(_location, _name),
 		Documented(_documentation),
-		ImplementationOptional(true),
 		m_baseContracts(_baseContracts),
 		m_definedStructs(_definedStructs),
 		m_definedEnums(_definedEnums),
@@ -261,24 +267,14 @@ public:
 	std::vector<ASTPointer<EventDefinition>> const& interfaceEvents() const;
 	bool isLibrary() const { return m_isLibrary; }
 
-	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
-
-	/// Checks that there are no illegal overrides, that the constructor does not have a "returns"
-	/// and calls checkTypeRequirements on all its functions.
-	void checkTypeRequirements();
-
 	/// @returns a map of canonical function signatures to FunctionDefinitions
 	/// as intended for use by the ABI.
 	std::map<FixedHash<4>, FunctionTypePointer> interfaceFunctions() const;
+	std::vector<std::pair<FixedHash<4>, FunctionTypePointer>> const& interfaceFunctionList() const;
 
 	/// @returns a list of the inheritable members of this contract
 	std::vector<Declaration const*> const& inheritableMembers() const;
 
-	/// List of all (direct and indirect) base contracts in order from derived to base, including
-	/// the contract itself. Available after name resolution
-	std::vector<ContractDefinition const*> const& linearizedBaseContracts() const { return m_linearizedBaseContracts; }
-	void setLinearizedBaseContracts(std::vector<ContractDefinition const*> const& _bases) { m_linearizedBaseContracts = _bases; }
-
 	/// Returns the constructor or nullptr if no constructor was specified.
 	FunctionDefinition const* constructor() const;
 	/// Returns the fallback function or nullptr if no fallback function was specified.
@@ -290,21 +286,9 @@ public:
 	std::string const& devDocumentation() const;
 	void setDevDocumentation(std::string const& _devDocumentation);
 
-private:
-	/// Checks that two functions defined in this contract with the same name have different
-	/// arguments and that there is at most one constructor.
-	void checkDuplicateFunctions() const;
-	void checkIllegalOverrides() const;
-	void checkAbstractFunctions();
-	void checkAbstractConstructors();
-	/// Checks that different functions with external visibility end up having different
-	/// external argument types (i.e. different signature).
-	void checkExternalTypeClashes() const;
-	/// Checks that all requirements for a library are fulfilled if this is a library.
-	void checkLibraryRequirements() const;
-
-	std::vector<std::pair<FixedHash<4>, FunctionTypePointer>> const& interfaceFunctionList() const;
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 
+private:
 	std::vector<ASTPointer<InheritanceSpecifier>> m_baseContracts;
 	std::vector<ASTPointer<StructDefinition>> m_definedStructs;
 	std::vector<ASTPointer<EnumDefinition>> m_definedEnums;
@@ -327,18 +311,19 @@ private:
 class InheritanceSpecifier: public ASTNode
 {
 public:
-	InheritanceSpecifier(SourceLocation const& _location, ASTPointer<Identifier> const& _baseName,
-						 std::vector<ASTPointer<Expression>> _arguments):
+	InheritanceSpecifier(
+		SourceLocation const& _location,
+		ASTPointer<Identifier> const& _baseName,
+		std::vector<ASTPointer<Expression>> _arguments
+	):
 		ASTNode(_location), m_baseName(_baseName), m_arguments(_arguments) {}
 
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
-	ASTPointer<Identifier> const& name() const { return m_baseName; }
+	Identifier const& name() const { return *m_baseName; }
 	std::vector<ASTPointer<Expression>> const& arguments() const { return m_arguments; }
 
-	void checkTypeRequirements();
-
 private:
 	ASTPointer<Identifier> m_baseName;
 	std::vector<ASTPointer<Expression>> m_arguments;
@@ -347,41 +332,38 @@ private:
 class StructDefinition: public Declaration
 {
 public:
-	StructDefinition(SourceLocation const& _location,
-					 ASTPointer<ASTString> const& _name,
-					 std::vector<ASTPointer<VariableDeclaration>> const& _members):
+	StructDefinition(
+		SourceLocation const& _location,
+		ASTPointer<ASTString> const& _name,
+		std::vector<ASTPointer<VariableDeclaration>> const& _members
+	):
 		Declaration(_location, _name), m_members(_members) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
 	std::vector<ASTPointer<VariableDeclaration>> const& members() const { return m_members; }
 
-	virtual TypePointer type(ContractDefinition const*) const override;
-
-	/// Checks that the members do not include any recursive structs and have valid types
-	/// (e.g. no functions).
-	void checkValidityOfMembers() const;
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 
 private:
-	void checkMemberTypes() const;
-	void checkRecursion() const;
-
 	std::vector<ASTPointer<VariableDeclaration>> m_members;
 };
 
 class EnumDefinition: public Declaration
 {
 public:
-	EnumDefinition(SourceLocation const& _location,
-				   ASTPointer<ASTString> const& _name,
-				   std::vector<ASTPointer<EnumValue>> const& _members):
+	EnumDefinition(
+		SourceLocation const& _location,
+		ASTPointer<ASTString> const& _name,
+		std::vector<ASTPointer<EnumValue>> const& _members
+	):
 		Declaration(_location, _name), m_members(_members) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
 	std::vector<ASTPointer<EnumValue>> const& members() const { return m_members; }
 
-	virtual TypePointer type(ContractDefinition const*) const override;
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 
 private:
 	std::vector<ASTPointer<EnumValue>> m_members;
@@ -392,14 +374,14 @@ private:
  */
 class EnumValue: public Declaration
 {
-  public:
-	EnumValue(SourceLocation const& _location,
-			  ASTPointer<ASTString> const& _name):
+public:
+	EnumValue(SourceLocation const& _location, ASTPointer<ASTString> const& _name):
 		Declaration(_location, _name) {}
 
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual TypePointer type(ContractDefinition const* = nullptr) const override;
+
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 };
 
 /**
@@ -488,17 +470,15 @@ public:
 	{
 		return Declaration::isVisibleInContract() && !isConstructor() && !name().empty();
 	}
-	virtual TypePointer type(ContractDefinition const*) const override;
 	virtual bool isPartOfExternalInterface() const override { return isPublic() && !m_isConstructor && !name().empty(); }
 
-	/// Checks that all parameters have allowed types and calls checkTypeRequirements on the body.
-	void checkTypeRequirements();
-
 	/// @returns the external signature of the function
 	/// That consists of the name of the function followed by the types of the
 	/// arguments separated by commas all enclosed in parentheses without any spaces.
 	std::string externalSignature() const;
 
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
+
 private:
 	bool m_isConstructor;
 	bool m_isDeclaredConst;
@@ -537,28 +517,27 @@ public:
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
-	TypeName* typeName() { return m_typeName.get(); }
+	TypeName* typeName() const { return m_typeName.get(); }
 	ASTPointer<Expression> const& value() const { return m_value; }
 
-	/// Returns the declared or inferred type. Can be an empty pointer if no type was explicitly
-	/// declared and there is no assignment to the variable that fixes the type.
-	TypePointer type(ContractDefinition const* = nullptr) const override { return m_type; }
-	void setType(std::shared_ptr<Type const> const& _type) { m_type = _type; }
-
 	virtual bool isLValue() const override;
 	virtual bool isPartOfExternalInterface() const override { return isPublic(); }
 
-	void checkTypeRequirements();
 	bool isLocalVariable() const { return !!dynamic_cast<FunctionDefinition const*>(scope()); }
 	/// @returns true if this variable is a parameter or return parameter of a function.
 	bool isCallableParameter() const;
 	/// @returns true if this variable is a parameter (not return parameter) of an external function.
 	bool isExternalCallableParameter() const;
+	/// @returns true if the type of the variable does not need to be specified, i.e. it is declared
+	/// in the body of a function or modifier.
+	bool canHaveAutoType() const;
 	bool isStateVariable() const { return m_isStateVariable; }
 	bool isIndexed() const { return m_isIndexed; }
 	bool isConstant() const { return m_isConstant; }
 	Location referenceLocation() const { return m_location; }
 
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
+
 protected:
 	Visibility defaultVisibility() const override { return Visibility::Internal; }
 
@@ -569,8 +548,6 @@ private:
 	bool m_isIndexed; ///< Whether this is an indexed variable (used by events).
 	bool m_isConstant; ///< Whether the variable is a compile-time constant.
 	Location m_location; ///< Location of the variable if it is of reference type.
-
-	std::shared_ptr<Type const> m_type; ///< derived type, initially empty
 };
 
 /**
@@ -597,9 +574,7 @@ public:
 
 	Block const& body() const { return *m_body; }
 
-	virtual TypePointer type(ContractDefinition const* = nullptr) const override;
-
-	void checkTypeRequirements();
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 
 private:
 	ASTPointer<Block> m_body;
@@ -611,8 +586,11 @@ private:
 class ModifierInvocation: public ASTNode
 {
 public:
-	ModifierInvocation(SourceLocation const& _location, ASTPointer<Identifier> const& _name,
-					   std::vector<ASTPointer<Expression>> _arguments):
+	ModifierInvocation(
+		SourceLocation const& _location,
+		ASTPointer<Identifier> const& _name,
+		std::vector<ASTPointer<Expression>> _arguments
+	):
 		ASTNode(_location), m_modifierName(_name), m_arguments(_arguments) {}
 
 	virtual void accept(ASTVisitor& _visitor) override;
@@ -621,9 +599,6 @@ public:
 	ASTPointer<Identifier> const& name() const { return m_modifierName; }
 	std::vector<ASTPointer<Expression>> const& arguments() const { return m_arguments; }
 
-	/// @param _bases is the list of base contracts for base constructor calls. For modifiers an empty vector should be passed.
-	void checkTypeRequirements(std::vector<ContractDefinition const*> const& _bases);
-
 private:
 	ASTPointer<Identifier> m_modifierName;
 	std::vector<ASTPointer<Expression>> m_arguments;
@@ -653,12 +628,7 @@ public:
 
 	bool isAnonymous() const { return m_anonymous; }
 
-	virtual TypePointer type(ContractDefinition const* = nullptr) const override
-	{
-		return std::make_shared<FunctionType>(*this);
-	}
-
-	void checkTypeRequirements();
+	virtual TypePointer type(ContractDefinition const* m_currentContract) const override;
 
 private:
 	bool m_anonymous = false;
@@ -678,7 +648,7 @@ public:
 	virtual void accept(ASTConstVisitor&) const override { BOOST_THROW_EXCEPTION(InternalCompilerError()
 							<< errinfo_comment("MagicVariableDeclaration used inside real AST.")); }
 
-	virtual TypePointer type(ContractDefinition const* = nullptr) const override { return m_type; }
+	virtual TypePointer type(ContractDefinition const*) const override { return m_type; }
 
 private:
 	std::shared_ptr<Type const> m_type;
@@ -696,11 +666,6 @@ public:
 	explicit TypeName(SourceLocation const& _location): ASTNode(_location) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-
-	/// Retrieve the element of the type hierarchy this node refers to. Can return an empty shared
-	/// pointer until the types have been resolved using the @ref NameAndTypeResolver.
-	/// If it returns an empty shared pointer after that, this indicates that the type was not found.
-	virtual std::shared_ptr<Type const> toType() = 0;
 };
 
 /**
@@ -717,7 +682,6 @@ public:
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual std::shared_ptr<Type const> toType() override { return Type::fromElementaryTypeName(m_type); }
 
 	Token::Value typeName() const { return m_type; }
 
@@ -732,19 +696,14 @@ class UserDefinedTypeName: public TypeName
 {
 public:
 	UserDefinedTypeName(SourceLocation const& _location, ASTPointer<ASTString> const& _name):
-		TypeName(_location), m_name(_name), m_referencedDeclaration(nullptr) {}
+		TypeName(_location), m_name(_name) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual std::shared_ptr<Type const> toType() override { return Type::fromUserDefinedTypeName(*this); }
 
 	ASTString const& name() const { return *m_name; }
-	void setReferencedDeclaration(Declaration const& _referencedDeclaration) { m_referencedDeclaration = &_referencedDeclaration; }
-	Declaration const* referencedDeclaration() const { return m_referencedDeclaration; }
 
 private:
 	ASTPointer<ASTString> m_name;
-
-	Declaration const* m_referencedDeclaration;
 };
 
 /**
@@ -758,7 +717,6 @@ public:
 		TypeName(_location), m_keyType(_keyType), m_valueType(_valueType) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual TypePointer toType() override { return Type::fromMapping(*m_keyType, *m_valueType); }
 
 	ElementaryTypeName const& keyType() const { return *m_keyType; }
 	TypeName const& valueType() const { return *m_valueType; }
@@ -779,7 +737,6 @@ public:
 		TypeName(_location), m_baseType(_baseType), m_length(_length) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual std::shared_ptr<Type const> toType() override { return Type::fromArrayTypeName(*m_baseType, m_length.get()); }
 
 	TypeName const& baseType() const { return *m_baseType; }
 	Expression const* length() const { return m_length.get(); }
@@ -802,11 +759,6 @@ class Statement: public ASTNode
 {
 public:
 	explicit Statement(SourceLocation const& _location): ASTNode(_location) {}
-
-	/// Check all type requirements, throws exception if some requirement is not met.
-	/// This includes checking that operators are applicable to their arguments but also that
-	/// the number of function call arguments matches the number of formal parameters and so forth.
-	virtual void checkTypeRequirements() = 0;
 };
 
 /**
@@ -820,8 +772,6 @@ public:
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
-	virtual void checkTypeRequirements() override;
-
 private:
 	std::vector<ASTPointer<Statement>> m_statements;
 };
@@ -837,8 +787,6 @@ public:
 
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-
-	virtual void checkTypeRequirements() override { }
 };
 
 /**
@@ -854,7 +802,6 @@ public:
 		m_condition(_condition), m_trueBody(_trueBody), m_falseBody(_falseBody) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
 	Expression const& condition() const { return *m_condition; }
 	Statement const& trueStatement() const { return *m_trueBody; }
@@ -884,7 +831,6 @@ public:
 		BreakableStatement(_location), m_condition(_condition), m_body(_body) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
 	Expression const& condition() const { return *m_condition; }
 	Statement const& body() const { return *m_body; }
@@ -900,19 +846,21 @@ private:
 class ForStatement: public BreakableStatement
 {
 public:
-	ForStatement(SourceLocation const& _location,
-				 ASTPointer<Statement> const& _initExpression,
-				 ASTPointer<Expression> const& _conditionExpression,
-				 ASTPointer<ExpressionStatement> const& _loopExpression,
-				 ASTPointer<Statement> const& _body):
+	ForStatement(
+		SourceLocation const& _location,
+		ASTPointer<Statement> const& _initExpression,
+		ASTPointer<Expression> const& _conditionExpression,
+		ASTPointer<ExpressionStatement> const& _loopExpression,
+		ASTPointer<Statement> const& _body
+	):
 		BreakableStatement(_location),
 		m_initExpression(_initExpression),
 		m_condExpression(_conditionExpression),
 		m_loopExpression(_loopExpression),
-		m_body(_body) {}
+		m_body(_body)
+	{}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
 	Statement const* initializationExpression() const { return m_initExpression.get(); }
 	Expression const* condition() const { return m_condExpression.get(); }
@@ -936,7 +884,6 @@ public:
 	Continue(SourceLocation const& _location): Statement(_location) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override {}
 };
 
 class Break: public Statement
@@ -945,27 +892,20 @@ public:
 	Break(SourceLocation const& _location): Statement(_location) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override {}
 };
 
 class Return: public Statement
 {
 public:
 	Return(SourceLocation const& _location, ASTPointer<Expression> _expression):
-		Statement(_location), m_expression(_expression), m_returnParameters(nullptr) {}
+		Statement(_location), m_expression(_expression) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
-	void setFunctionReturnParameters(ParameterList const* _parameters) { m_returnParameters = _parameters; }
-	ParameterList const* functionReturnParameters() const { return m_returnParameters; }
 	Expression const* expression() const { return m_expression.get(); }
 
 private:
 	ASTPointer<Expression> m_expression; ///< value to return, optional
-
-	/// Pointer to the parameter list of the function, filled by the @ref NameAndTypeResolver.
-	ParameterList const* m_returnParameters;
 };
 
 /**
@@ -977,7 +917,6 @@ public:
 	Throw(SourceLocation const& _location): Statement(_location) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override {};
 };
 
 /**
@@ -992,7 +931,6 @@ public:
 		Statement(_location), m_variable(_variable) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
 	VariableDeclaration const& declaration() const { return *m_variable; }
 	Expression const* expression() const { return m_variable->value().get(); }
@@ -1011,7 +949,6 @@ public:
 		Statement(_location), m_expression(_expression) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements() override;
 
 	Expression const& expression() const { return *m_expression; }
 
@@ -1033,32 +970,6 @@ class Expression: public ASTNode
 {
 public:
 	Expression(SourceLocation const& _location): ASTNode(_location) {}
-	/// Performs type checking after which m_type should be set.
-	/// @arg _argumentTypes if set, provides the argument types for the case that this expression
-	/// is used in the context of a call, used for function overload resolution.
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) = 0;
-
-	std::shared_ptr<Type const> const& type() const { return m_type; }
-	bool isLValue() const { return m_isLValue; }
-
-	/// Helper function, infer the type via @ref checkTypeRequirements and then check that it
-	/// is implicitly convertible to @a _expectedType. If not, throw exception.
-	void expectType(Type const& _expectedType);
-	/// Checks that this expression is an lvalue and also registers that an address and
-	/// not a value is generated during compilation. Can be called after checkTypeRequirements()
-	/// by an enclosing expression.
-	void requireLValue();
-	/// Returns true if @a requireLValue was previously called on this expression.
-	bool lvalueRequested() const { return m_lvalueRequested; }
-
-protected:
-	//! Inferred type of the expression, only filled after a call to checkTypeRequirements().
-	std::shared_ptr<Type const> m_type;
-	//! If this expression is an lvalue (i.e. something that can be assigned to).
-	//! This is set during calls to @a checkTypeRequirements()
-	bool m_isLValue = false;
-	//! Whether the outer expression requested the address (true) or the value (false) of this expression.
-	bool m_lvalueRequested = false;
 };
 
 /// Assignment, can also be a compound assignment.
@@ -1066,16 +977,21 @@ protected:
 class Assignment: public Expression
 {
 public:
-	Assignment(SourceLocation const& _location, ASTPointer<Expression> const& _leftHandSide,
-			   Token::Value _assignmentOperator, ASTPointer<Expression> const& _rightHandSide):
-		Expression(_location), m_leftHandSide(_leftHandSide),
-		m_assigmentOperator(_assignmentOperator), m_rightHandSide(_rightHandSide)
+	Assignment(
+		SourceLocation const& _location,
+		ASTPointer<Expression> const& _leftHandSide,
+		Token::Value _assignmentOperator,
+		ASTPointer<Expression> const& _rightHandSide
+	):
+		Expression(_location),
+		m_leftHandSide(_leftHandSide),
+		m_assigmentOperator(_assignmentOperator),
+		m_rightHandSide(_rightHandSide)
 	{
 		solAssert(Token::isAssignmentOp(_assignmentOperator), "");
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Expression const& leftHandSide() const { return *m_leftHandSide; }
 	Token::Value assignmentOperator() const { return m_assigmentOperator; }
@@ -1103,7 +1019,6 @@ public:
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Token::Value getOperator() const { return m_operator; }
 	bool isPrefixOperation() const { return m_isPrefix; }
@@ -1130,21 +1045,15 @@ public:
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Expression const& leftExpression() const { return *m_left; }
 	Expression const& rightExpression() const { return *m_right; }
 	Token::Value getOperator() const { return m_operator; }
-	Type const& commonType() const { return *m_commonType; }
 
 private:
 	ASTPointer<Expression> m_left;
 	Token::Value m_operator;
 	ASTPointer<Expression> m_right;
-
-	/// The common type that is used for the operation, not necessarily the result type (e.g. for
-	/// comparisons, this is always bool).
-	std::shared_ptr<Type const> m_commonType;
 };
 
 /**
@@ -1158,18 +1067,11 @@ public:
 		Expression(_location), m_expression(_expression), m_arguments(_arguments), m_names(_names) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Expression const& expression() const { return *m_expression; }
 	std::vector<ASTPointer<Expression const>> arguments() const { return {m_arguments.begin(), m_arguments.end()}; }
 	std::vector<ASTPointer<ASTString>> const& names() const { return m_names; }
 
-	/// @returns true if this is not an actual function call, but an explicit type conversion.
-	/// Returns false for struct constructor calls.
-	bool isTypeConversion() const;
-	/// @return true if this is a constructor call for a struct, i.e. StructName(...).
-	bool isStructConstructorCall() const;
-
 private:
 	ASTPointer<Expression> m_expression;
 	std::vector<ASTPointer<Expression>> m_arguments;
@@ -1186,15 +1088,11 @@ public:
 		Expression(_location), m_contractName(_contractName) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
-	/// Returns the referenced contract. Can only be called after type checking.
-	ContractDefinition const* contract() const { solAssert(m_contract, ""); return m_contract; }
+	Identifier const& contractName() const { return *m_contractName; }
 
 private:
 	ASTPointer<Identifier> m_contractName;
-
-	ContractDefinition const* m_contract = nullptr;
 };
 
 /**
@@ -1210,18 +1108,10 @@ public:
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 	Expression const& expression() const { return *m_expression; }
 	ASTString const& memberName() const { return *m_memberName; }
-	/// @returns the declaration referenced by this expression. Might return nullptr even if the
-	/// expression is valid, e.g. if the member does not correspond to an AST node.
-	Declaration const* referencedDeclaration() const { return m_referencedDeclaration; }
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 private:
 	ASTPointer<Expression> m_expression;
 	ASTPointer<ASTString> m_memberName;
-
-	/// Pointer to the referenced declaration, this is sometimes needed to resolve function over
-	/// loads in the type-checking phase.
-	Declaration const* m_referencedDeclaration = nullptr;
 };
 
 /**
@@ -1235,7 +1125,6 @@ public:
 		Expression(_location), m_base(_base), m_index(_index) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Expression const& baseExpression() const { return *m_base; }
 	Expression const* indexExpression() const { return m_index.get(); }
@@ -1265,44 +1154,11 @@ public:
 		PrimaryExpression(_location), m_name(_name) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	ASTString const& name() const { return *m_name; }
 
-	void setReferencedDeclaration(
-		Declaration const& _referencedDeclaration,
-		ContractDefinition const* _currentContract = nullptr
-	)
-	{
-		m_referencedDeclaration = &_referencedDeclaration;
-		m_contractScope = _currentContract;
-	}
-	Declaration const& referencedDeclaration() const;
-
-	/// Stores a set of possible declarations referenced by this identifier. Has to be resolved
-	/// providing argument types using overloadResolution before the referenced declaration
-	/// is accessed.
-	void setOverloadedDeclarations(std::vector<Declaration const*> const& _declarations)
-	{
-		m_overloadedDeclarations = _declarations;
-	}
-
-	/// Tries to find exactly one of the possible referenced declarations provided the given
-	/// argument types in a call context.
-	void overloadResolution(TypePointers const& _argumentTypes);
-
-	ContractDefinition const* contractScope() const { return m_contractScope; }
-
 private:
 	ASTPointer<ASTString> m_name;
-
-	/// Declaration the name refers to.
-	Declaration const* m_referencedDeclaration = nullptr;
-	/// Stores a reference to the current contract. This is needed because types of base contracts
-	/// change depending on the context.
-	ContractDefinition const* m_contractScope = nullptr;
-	/// A vector of overloaded declarations, right now only FunctionDefinition has overloaded declarations.
-	std::vector<Declaration const*> m_overloadedDeclarations;
 };
 
 /**
@@ -1320,7 +1176,6 @@ public:
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Token::Value typeToken() const { return m_typeToken; }
 
@@ -1354,7 +1209,6 @@ public:
 		PrimaryExpression(_location), m_token(_token), m_value(_value), m_subDenomination(_sub) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
-	virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;
 
 	Token::Value token() const { return m_token; }
 	/// @returns the non-parsed value of the literal
diff --git a/libsolidity/ASTAnnotations.cpp b/libsolidity/ASTAnnotations.cpp
new file mode 100644
index 00000000..4253e16d
--- /dev/null
+++ b/libsolidity/ASTAnnotations.cpp
@@ -0,0 +1,28 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Object containing the type and other annotations for the AST nodes.
+ */
+
+#include <libsolidity/ASTAnnotations.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
diff --git a/libsolidity/ASTAnnotations.h b/libsolidity/ASTAnnotations.h
new file mode 100644
index 00000000..9564d2d0
--- /dev/null
+++ b/libsolidity/ASTAnnotations.h
@@ -0,0 +1,78 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Object containing the type and other annotations for the AST nodes.
+ */
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <vector>
+
+namespace dev
+{
+namespace solidity
+{
+
+class ASTNode;
+class ContractDefinition;
+class Declaration;
+class ParameterList;
+class Type;
+using TypePointer = std::shared_ptr<Type const>;
+
+struct ASTAnnotation
+{
+	///@TODO save space here - we do not need all members for all types.
+
+	/// For expression: Inferred type. - For type declaration: Declared type. - For variable declaration: Type of variable.
+	TypePointer type;
+	/// For expression: Whether it is an LValue (i.e. something that can be assigned to).
+	bool isLValue = false;
+	/// For expression: Whether the expression is used in a context where the LValue is actually required.
+	bool lValueRequested = false;
+	/// For expressions: Types of arguments if the expression is a function that is called - used
+	/// for overload resolution.
+	std::shared_ptr<std::vector<TypePointer>> argumentTypes;
+	/// For contract: Whether all functions are implemented.
+	bool isFullyImplemented = true;
+	/// For contract: List of all (direct and indirect) base contracts in order from derived to
+	/// base, including the contract itself.
+	std::vector<ContractDefinition const*> linearizedBaseContracts;
+	/// For member access and Identifer: Referenced declaration, set during overload resolution stage.
+	Declaration const* referencedDeclaration = nullptr;
+	/// For Identifier: List of possible declarations it could refer to.
+	std::vector<Declaration const*> overloadedDeclarations;
+	/// For function call: Whether this is an explicit type conversion.
+	bool isTypeConversion = false;
+	/// For function call: Whether this is a struct constructor call.
+	bool isStructConstructorCall = false;
+	/// For Return statement: Reference to the return parameters of the function.
+	ParameterList const* functionReturnParameters = nullptr;
+	/// For Identifier: Stores a reference to the current contract.
+	/// This is needed because types of base contracts change depending on the context.
+	ContractDefinition const* contractScope = nullptr;
+	/// For BinaryOperation: The common type that is used for the operation, not necessarily the result type (e.g. for
+	/// comparisons, this is always bool).
+	TypePointer commonType;
+};
+
+}
+}
diff --git a/libsolidity/ASTJsonConverter.cpp b/libsolidity/ASTJsonConverter.cpp
index 96e5cf2a..3edcb77e 100644
--- a/libsolidity/ASTJsonConverter.cpp
+++ b/libsolidity/ASTJsonConverter.cpp
@@ -232,19 +232,19 @@ bool ASTJsonConverter::visit(UnaryOperation const& _node)
 
 bool ASTJsonConverter::visit(BinaryOperation const& _node)
 {
-	addJsonNode("BinaryOperation",
-				{ make_pair("operator", Token::toString(_node.getOperator())),
-					make_pair("type", type(_node))},
-				true);
+	addJsonNode("BinaryOperation", {
+		make_pair("operator", Token::toString(_node.getOperator())),
+		make_pair("type", type(_node))
+	}, true);
 	return true;
 }
 
 bool ASTJsonConverter::visit(FunctionCall const& _node)
 {
-	addJsonNode("FunctionCall",
-				{ make_pair("type_conversion", boost::lexical_cast<std::string>(_node.isTypeConversion())),
-					make_pair("type", type(_node)) },
-				true);
+	addJsonNode("FunctionCall", {
+		make_pair("type_conversion", boost::lexical_cast<std::string>(_node.annotation().isTypeConversion)),
+		make_pair("type", type(_node))
+	}, true);
 	return true;
 }
 
@@ -441,7 +441,7 @@ void ASTJsonConverter::process()
 
 string ASTJsonConverter::type(Expression const& _expression)
 {
-	return (_expression.type()) ? _expression.type()->toString() : "Unknown";
+	return _expression.annotation().type ? _expression.annotation().type->toString() : "Unknown";
 }
 
 }
diff --git a/libsolidity/ASTJsonConverter.h b/libsolidity/ASTJsonConverter.h
index 77230d92..a44df876 100644
--- a/libsolidity/ASTJsonConverter.h
+++ b/libsolidity/ASTJsonConverter.h
@@ -27,6 +27,7 @@
 #include <libsolidity/ASTVisitor.h>
 #include <libsolidity/Exceptions.h>
 #include <libsolidity/Utils.h>
+#include <libsolidity/ASTAnnotations.h>
 #include <json/json.h>
 
 namespace dev
@@ -41,7 +42,7 @@ class ASTJsonConverter: public ASTConstVisitor
 {
 public:
 	/// Create a converter to JSON for the given abstract syntax tree.
-	ASTJsonConverter(ASTNode const& _ast);
+	explicit ASTJsonConverter(ASTNode const& _ast);
 	/// Output the json representation of the AST to _stream.
 	void print(std::ostream& _stream);
 	Json::Value const& json();
diff --git a/libsolidity/ASTPrinter.cpp b/libsolidity/ASTPrinter.cpp
index 8ed45d87..5762051d 100644
--- a/libsolidity/ASTPrinter.cpp
+++ b/libsolidity/ASTPrinter.cpp
@@ -62,7 +62,7 @@ bool ASTPrinter::visit(ContractDefinition const& _node)
 
 bool ASTPrinter::visit(InheritanceSpecifier const& _node)
 {
-	writeLine("InheritanceSpecifier \"" + _node.name()->name() + "\"");
+	writeLine("InheritanceSpecifier \"" + _node.name().name() + "\"");
 	printSourcePart(_node);
 	return goDeeper();
 }
@@ -530,8 +530,8 @@ void ASTPrinter::printSourcePart(ASTNode const& _node)
 
 void ASTPrinter::printType(Expression const& _expression)
 {
-	if (_expression.type())
-		*m_ostream << indentation() << "   Type: " << _expression.type()->toString() << "\n";
+	if (_expression.annotation().type)
+		*m_ostream << indentation() << "   Type: " << _expression.annotation().type->toString() << "\n";
 	else
 		*m_ostream << indentation() << "   Type unknown.\n";
 }
diff --git a/libsolidity/AST_accept.h b/libsolidity/AST_accept.h
index 1388466c..dfa9c425 100644
--- a/libsolidity/AST_accept.h
+++ b/libsolidity/AST_accept.h
@@ -147,12 +147,6 @@ void StructDefinition::accept(ASTConstVisitor& _visitor) const
 	_visitor.endVisit(*this);
 }
 
-void StructDefinition::checkValidityOfMembers() const
-{
-	checkMemberTypes();
-	checkRecursion();
-}
-
 void ParameterList::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))
diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index d6582653..cb74072d 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -53,7 +53,7 @@ void Compiler::compileContract(
 	std::map<const ContractDefinition*, eth::Assembly const*> const& _contracts
 )
 {
-	m_context = CompilerContext(); // clear it just in case
+	m_context = CompilerContext();
 	{
 		CompilerContext::LocationSetter locationSetterRunTime(m_context, _contract);
 		initializeContext(_contract, _contracts);
@@ -105,9 +105,9 @@ void Compiler::initializeContext(
 	map<ContractDefinition const*, eth::Assembly const*> const& _compiledContracts
 )
 {
-	CompilerUtils(m_context).initialiseFreeMemoryPointer();
 	m_context.setCompiledContracts(_compiledContracts);
-	m_context.setInheritanceHierarchy(_contract.linearizedBaseContracts());
+	m_context.setInheritanceHierarchy(_contract.annotation().linearizedBaseContracts);
+	CompilerUtils(m_context).initialiseFreeMemoryPointer();
 	registerStateVariables(_contract);
 	m_context.resetVisitedNodes(&_contract);
 }
@@ -115,14 +115,14 @@ void Compiler::initializeContext(
 void Compiler::appendInitAndConstructorCode(ContractDefinition const& _contract)
 {
 	// Determine the arguments that are used for the base constructors.
-	std::vector<ContractDefinition const*> const& bases = _contract.linearizedBaseContracts();
+	std::vector<ContractDefinition const*> const& bases = _contract.annotation().linearizedBaseContracts;
 	for (ContractDefinition const* contract: bases)
 	{
 		if (FunctionDefinition const* constructor = contract->constructor())
 			for (auto const& modifier: constructor->modifiers())
 			{
 				auto baseContract = dynamic_cast<ContractDefinition const*>(
-					&modifier->name()->referencedDeclaration());
+					modifier->name()->annotation().referencedDeclaration);
 				if (baseContract)
 					if (m_baseArguments.count(baseContract->constructor()) == 0)
 						m_baseArguments[baseContract->constructor()] = &modifier->arguments();
@@ -131,7 +131,8 @@ void Compiler::appendInitAndConstructorCode(ContractDefinition const& _contract)
 		for (ASTPointer<InheritanceSpecifier> const& base: contract->baseContracts())
 		{
 			ContractDefinition const* baseContract = dynamic_cast<ContractDefinition const*>(
-						&base->name()->referencedDeclaration());
+				base->name().annotation().referencedDeclaration
+			);
 			solAssert(baseContract, "");
 
 			if (m_baseArguments.count(baseContract->constructor()) == 0)
@@ -187,13 +188,13 @@ void Compiler::appendConstructor(FunctionDefinition const& _constructor)
 	{
 		unsigned argumentSize = 0;
 		for (ASTPointer<VariableDeclaration> const& var: _constructor.parameters())
-			if (var->type()->isDynamicallySized())
+			if (var->annotation().type->isDynamicallySized())
 			{
 				argumentSize = 0;
 				break;
 			}
 			else
-				argumentSize += var->type()->calldataEncodedSize();
+				argumentSize += var->annotation().type->calldataEncodedSize();
 
 		CompilerUtils(m_context).fetchFreeMemoryPointer();
 		if (argumentSize == 0)
@@ -418,7 +419,7 @@ bool Compiler::visit(FunctionDefinition const& _function)
 	for (ASTPointer<VariableDeclaration const> const& variable: _function.parameters())
 	{
 		m_context.addVariable(*variable, parametersSize);
-		parametersSize -= variable->type()->sizeOnStack();
+		parametersSize -= variable->annotation().type->sizeOnStack();
 	}
 
 	for (ASTPointer<VariableDeclaration const> const& variable: _function.returnParameters())
@@ -594,9 +595,9 @@ bool Compiler::visit(Return const& _return)
 	//@todo modifications are needed to make this work with functions returning multiple values
 	if (Expression const* expression = _return.expression())
 	{
-		solAssert(_return.functionReturnParameters(), "Invalid return parameters pointer.");
-		VariableDeclaration const& firstVariable = *_return.functionReturnParameters()->parameters().front();
-		compileExpression(*expression, firstVariable.type());
+		solAssert(_return.annotation().functionReturnParameters, "Invalid return parameters pointer.");
+		VariableDeclaration const& firstVariable = *_return.annotation().functionReturnParameters->parameters().front();
+		compileExpression(*expression, firstVariable.annotation().type);
 		CompilerUtils(m_context).moveToStackVariable(firstVariable);
 	}
 	for (unsigned i = 0; i < m_stackCleanupForReturn; ++i)
@@ -619,7 +620,7 @@ bool Compiler::visit(VariableDeclarationStatement const& _variableDeclarationSta
 	CompilerContext::LocationSetter locationSetter(m_context, _variableDeclarationStatement);
 	if (Expression const* expression = _variableDeclarationStatement.expression())
 	{
-		compileExpression(*expression, _variableDeclarationStatement.declaration().type());
+		compileExpression(*expression, _variableDeclarationStatement.declaration().annotation().type);
 		CompilerUtils(m_context).moveToStackVariable(_variableDeclarationStatement.declaration());
 	}
 	checker.check();
@@ -632,7 +633,7 @@ bool Compiler::visit(ExpressionStatement const& _expressionStatement)
 	CompilerContext::LocationSetter locationSetter(m_context, _expressionStatement);
 	Expression const& expression = _expressionStatement.expression();
 	compileExpression(expression);
-	CompilerUtils(m_context).popStackElement(*expression.type());
+	CompilerUtils(m_context).popStackElement(*expression.annotation().type);
 	checker.check();
 	return false;
 }
@@ -672,7 +673,7 @@ void Compiler::appendModifierOrFunctionCode()
 		ASTPointer<ModifierInvocation> const& modifierInvocation = m_currentFunction->modifiers()[m_modifierDepth];
 
 		// constructor call should be excluded
-		if (dynamic_cast<ContractDefinition const*>(&modifierInvocation->name()->referencedDeclaration()))
+		if (dynamic_cast<ContractDefinition const*>(modifierInvocation->name()->annotation().referencedDeclaration))
 		{
 			++m_modifierDepth;
 			appendModifierOrFunctionCode();
@@ -688,7 +689,7 @@ void Compiler::appendModifierOrFunctionCode()
 			m_context.addVariable(*modifier.parameters()[i]);
 			compileExpression(
 				*modifierInvocation->arguments()[i],
-				modifier.parameters()[i]->type()
+				modifier.parameters()[i]->annotation().type
 			);
 		}
 		for (VariableDeclaration const* localVariable: modifier.localVariables())
@@ -710,7 +711,7 @@ void Compiler::appendStackVariableInitialisation(VariableDeclaration const& _var
 {
 	CompilerContext::LocationSetter location(m_context, _variable);
 	m_context.addVariable(_variable);
-	CompilerUtils(m_context).pushZeroValue(*_variable.type());
+	CompilerUtils(m_context).pushZeroValue(*_variable.annotation().type);
 }
 
 void Compiler::compileExpression(Expression const& _expression, TypePointer const& _targetType)
@@ -718,7 +719,7 @@ void Compiler::compileExpression(Expression const& _expression, TypePointer cons
 	ExpressionCompiler expressionCompiler(m_context, m_optimize);
 	expressionCompiler.compile(_expression);
 	if (_targetType)
-		CompilerUtils(m_context).convertType(*_expression.type(), *_targetType);
+		CompilerUtils(m_context).convertType(*_expression.annotation().type, *_targetType);
 }
 
 eth::Assembly Compiler::cloneRuntime()
diff --git a/libsolidity/Compiler.h b/libsolidity/Compiler.h
index c7dd7d90..7b7cffcf 100644
--- a/libsolidity/Compiler.h
+++ b/libsolidity/Compiler.h
@@ -37,10 +37,8 @@ public:
 	explicit Compiler(bool _optimize = false, unsigned _runs = 200):
 		m_optimize(_optimize),
 		m_optimizeRuns(_runs),
-		m_context(),
 		m_returnTag(m_context.newTag())
-	{
-	}
+	{ }
 
 	void compileContract(
 		ContractDefinition const& _contract,
@@ -71,7 +69,8 @@ public:
 	eth::AssemblyItem functionEntryLabel(FunctionDefinition const& _function) const;
 
 private:
-	/// Registers the non-function objects inside the contract with the context.
+	/// Registers the non-function objects inside the contract with the context and stores the basic
+	/// information about the contract like the AST annotations.
 	void initializeContext(
 		ContractDefinition const& _contract,
 		std::map<ContractDefinition const*, eth::Assembly const*> const& _compiledContracts
diff --git a/libsolidity/CompilerContext.h b/libsolidity/CompilerContext.h
index 39f4e75f..46ebfcf8 100644
--- a/libsolidity/CompilerContext.h
+++ b/libsolidity/CompilerContext.h
@@ -29,6 +29,7 @@
 #include <libevmasm/Assembly.h>
 #include <libsolidity/ASTForward.h>
 #include <libsolidity/Types.h>
+#include <libsolidity/ASTAnnotations.h>
 #include <libdevcore/Common.h>
 
 namespace dev {
diff --git a/libsolidity/CompilerStack.cpp b/libsolidity/CompilerStack.cpp
index 70bb1b4c..b8139187 100644
--- a/libsolidity/CompilerStack.cpp
+++ b/libsolidity/CompilerStack.cpp
@@ -27,6 +27,7 @@
 #include <libsolidity/Parser.h>
 #include <libsolidity/GlobalContext.h>
 #include <libsolidity/NameAndTypeResolver.h>
+#include <libsolidity/TypeChecker.h>
 #include <libsolidity/Compiler.h>
 #include <libsolidity/CompilerStack.h>
 #include <libsolidity/InterfaceHandler.h>
@@ -123,7 +124,12 @@ void CompilerStack::parse()
 			{
 				m_globalContext->setCurrentContract(*contract);
 				resolver.updateDeclaration(*m_globalContext->currentThis());
-				resolver.checkTypeRequirements(*contract);
+				TypeChecker typeChecker;
+				bool typesFine = typeChecker.checkTypeRequirements(*contract);
+				if (!typesFine)
+					BOOST_THROW_EXCEPTION(*typeChecker.errors().front());
+				//@todo extract warnings and errors
+				// store whether we had an error
 				contract->setDevDocumentation(interfaceHandler.devDocumentation(*contract));
 				contract->setUserDocumentation(interfaceHandler.userDocumentation(*contract));
 				m_contracts[contract->name()].contract = contract;
@@ -153,12 +159,14 @@ void CompilerStack::compile(bool _optimize, unsigned _runs)
 	if (!m_parseSuccessful)
 		parse();
 
+	//@todo do not compile or error (also in other places)
+
 	map<ContractDefinition const*, eth::Assembly const*> compiledContracts;
 	for (Source const* source: m_sourceOrder)
 		for (ASTPointer<ASTNode> const& node: source->ast->nodes())
 			if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
 			{
-				if (!contract->isFullyImplemented())
+				if (!contract->annotation().isFullyImplemented)
 					continue;
 				shared_ptr<Compiler> compiler = make_shared<Compiler>(_optimize, _runs);
 				compiler->compileContract(*contract, compiledContracts);
diff --git a/libsolidity/CompilerStack.h b/libsolidity/CompilerStack.h
index 99e8af1a..4d9c1ec5 100644
--- a/libsolidity/CompilerStack.h
+++ b/libsolidity/CompilerStack.h
@@ -79,7 +79,9 @@ public:
 
 	/// Adds a source object (e.g. file) to the parser. After this, parse has to be called again.
 	/// @returns true if a source object by the name already existed and was replaced.
-	void addSources(StringMap const& _nameContents, bool _isLibrary = false) { for (auto const& i: _nameContents) addSource(i.first, i.second, _isLibrary); }
+	void addSources(StringMap const& _nameContents, bool _isLibrary = false) {
+		for (auto const& i: _nameContents) addSource(i.first, i.second, _isLibrary);
+	}
 	bool addSource(std::string const& _name, std::string const& _content, bool _isLibrary = false);
 	void setSource(std::string const& _sourceCode);
 	/// Parses all source units that were added
diff --git a/libsolidity/CompilerUtils.cpp b/libsolidity/CompilerUtils.cpp
index e370c6be..b9b554e8 100644
--- a/libsolidity/CompilerUtils.cpp
+++ b/libsolidity/CompilerUtils.cpp
@@ -600,7 +600,7 @@ void CompilerUtils::pushZeroValue(const Type& _type)
 void CompilerUtils::moveToStackVariable(VariableDeclaration const& _variable)
 {
 	unsigned const stackPosition = m_context.baseToCurrentStackOffset(m_context.baseStackOffsetOfVariable(_variable));
-	unsigned const size = _variable.type()->sizeOnStack();
+	unsigned const size = _variable.annotation().type->sizeOnStack();
 	solAssert(stackPosition >= size, "Variable size and position mismatch.");
 	// move variable starting from its top end in the stack
 	if (stackPosition - size + 1 > 16)
diff --git a/libsolidity/CompilerUtils.h b/libsolidity/CompilerUtils.h
index 0875ddd2..568a6307 100644
--- a/libsolidity/CompilerUtils.h
+++ b/libsolidity/CompilerUtils.h
@@ -170,7 +170,7 @@ unsigned CompilerUtils::sizeOnStack(std::vector<T> const& _variables)
 {
 	unsigned size = 0;
 	for (T const& variable: _variables)
-		size += variable->type()->sizeOnStack();
+		size += variable->annotation().type->sizeOnStack();
 	return size;
 }
 
diff --git a/libsolidity/ConstantEvaluator.cpp b/libsolidity/ConstantEvaluator.cpp
new file mode 100644
index 00000000..5936b3d4
--- /dev/null
+++ b/libsolidity/ConstantEvaluator.cpp
@@ -0,0 +1,59 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Evaluator for types of constant expressions.
+ */
+
+#include <libsolidity/ConstantEvaluator.h>
+#include <libsolidity/AST.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
+
+void ConstantEvaluator::endVisit(UnaryOperation const& _operation)
+{
+	TypePointer const& subType = _operation.subExpression().annotation().type;
+	if (!dynamic_cast<IntegerConstantType const*>(subType.get()))
+		BOOST_THROW_EXCEPTION(_operation.subExpression().createTypeError("Invalid constant expression."));
+	TypePointer t = subType->unaryOperatorResult(_operation.getOperator());
+	_operation.annotation().type = t;
+}
+
+void ConstantEvaluator::endVisit(BinaryOperation const& _operation)
+{
+	TypePointer const& leftType = _operation.leftExpression().annotation().type;
+	TypePointer const& rightType = _operation.rightExpression().annotation().type;
+	if (!dynamic_cast<IntegerConstantType const*>(leftType.get()))
+		BOOST_THROW_EXCEPTION(_operation.leftExpression().createTypeError("Invalid constant expression."));
+	if (!dynamic_cast<IntegerConstantType const*>(rightType.get()))
+		BOOST_THROW_EXCEPTION(_operation.rightExpression().createTypeError("Invalid constant expression."));
+	TypePointer commonType = leftType->binaryOperatorResult(_operation.getOperator(), rightType);
+	if (Token::isCompareOp(_operation.getOperator()))
+		commonType = make_shared<BoolType>();
+	_operation.annotation().type = commonType;
+}
+
+void ConstantEvaluator::endVisit(Literal const& _literal)
+{
+	_literal.annotation().type = Type::forLiteral(_literal);
+	if (!_literal.annotation().type)
+		BOOST_THROW_EXCEPTION(_literal.createTypeError("Invalid literal value."));
+}
diff --git a/libsolidity/ConstantEvaluator.h b/libsolidity/ConstantEvaluator.h
new file mode 100644
index 00000000..cf3d2094
--- /dev/null
+++ b/libsolidity/ConstantEvaluator.h
@@ -0,0 +1,50 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Evaluator for types of constant expressions.
+ */
+
+#pragma once
+
+#include <libsolidity/ASTVisitor.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+class TypeChecker;
+
+/**
+ * Small drop-in replacement for TypeChecker to evaluate simple expressions of integer constants.
+ */
+class ConstantEvaluator: private ASTConstVisitor
+{
+public:
+	ConstantEvaluator(Expression const& _expr) { _expr.accept(*this); }
+
+private:
+	virtual void endVisit(BinaryOperation const& _operation);
+	virtual void endVisit(UnaryOperation const& _operation);
+	virtual void endVisit(Literal const& _literal);
+
+};
+
+}
+}
diff --git a/libsolidity/Exceptions.h b/libsolidity/Exceptions.h
index 4bb6644b..d5cb7eb5 100644
--- a/libsolidity/Exceptions.h
+++ b/libsolidity/Exceptions.h
@@ -38,6 +38,7 @@ struct DeclarationError: virtual Exception {};
 struct CompilerError: virtual Exception {};
 struct InternalCompilerError: virtual Exception {};
 struct DocstringParsingError: virtual Exception {};
+struct FatalError: virtual Exception {};
 
 using errorSourceLocationInfo = std::pair<std::string, SourceLocation>;
 
diff --git a/libsolidity/ExpressionCompiler.cpp b/libsolidity/ExpressionCompiler.cpp
index 1b9f2150..1fa70797 100644
--- a/libsolidity/ExpressionCompiler.cpp
+++ b/libsolidity/ExpressionCompiler.cpp
@@ -48,12 +48,12 @@ void ExpressionCompiler::appendStateVariableInitialization(VariableDeclaration c
 {
 	if (!_varDecl.value())
 		return;
-	TypePointer type = _varDecl.value()->type();
+	TypePointer type = _varDecl.value()->annotation().type;
 	solAssert(!!type, "Type information not available.");
 	CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
 	_varDecl.value()->accept(*this);
 
-	if (_varDecl.type()->dataStoredIn(DataLocation::Storage))
+	if (_varDecl.annotation().type->dataStoredIn(DataLocation::Storage))
 	{
 		// reference type, only convert value to mobile type and do final conversion in storeValue.
 		utils().convertType(*type, *type->mobileType());
@@ -61,8 +61,8 @@ void ExpressionCompiler::appendStateVariableInitialization(VariableDeclaration c
 	}
 	else
 	{
-		utils().convertType(*type, *_varDecl.type());
-		type = _varDecl.type();
+		utils().convertType(*type, *_varDecl.annotation().type);
+		type = _varDecl.annotation().type;
 	}
 	StorageItem(m_context, _varDecl).storeValue(*type, _varDecl.location(), true);
 }
@@ -71,10 +71,10 @@ void ExpressionCompiler::appendConstStateVariableAccessor(VariableDeclaration co
 {
 	solAssert(_varDecl.isConstant(), "");
 	_varDecl.value()->accept(*this);
-	utils().convertType(*_varDecl.value()->type(), *_varDecl.type());
+	utils().convertType(*_varDecl.value()->annotation().type, *_varDecl.annotation().type);
 
 	// append return
-	m_context << eth::dupInstruction(_varDecl.type()->sizeOnStack() + 1);
+	m_context << eth::dupInstruction(_varDecl.annotation().type->sizeOnStack() + 1);
 	m_context.appendJump(eth::AssemblyItem::JumpType::OutOfFunction);
 }
 
@@ -90,7 +90,7 @@ void ExpressionCompiler::appendStateVariableAccessor(VariableDeclaration const&
 	auto const& location = m_context.storageLocationOfVariable(_varDecl);
 	m_context << location.first << u256(location.second);
 
-	TypePointer returnType = _varDecl.type();
+	TypePointer returnType = _varDecl.annotation().type;
 
 	for (size_t i = 0; i < paramTypes.size(); ++i)
 	{
@@ -179,11 +179,11 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _assignment);
 	_assignment.rightHandSide().accept(*this);
-	TypePointer type = _assignment.rightHandSide().type();
-	if (!_assignment.type()->dataStoredIn(DataLocation::Storage))
+	TypePointer type = _assignment.rightHandSide().annotation().type;
+	if (!_assignment.annotation().type->dataStoredIn(DataLocation::Storage))
 	{
-		utils().convertType(*type, *_assignment.type());
-		type = _assignment.type();
+		utils().convertType(*type, *_assignment.annotation().type);
+		type = _assignment.annotation().type;
 	}
 	else
 	{
@@ -197,9 +197,9 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 	Token::Value op = _assignment.assignmentOperator();
 	if (op != Token::Assign) // compound assignment
 	{
-		solAssert(_assignment.type()->isValueType(), "Compound operators not implemented for non-value types.");
+		solAssert(_assignment.annotation().type->isValueType(), "Compound operators not implemented for non-value types.");
 		unsigned lvalueSize = m_currentLValue->sizeOnStack();
-		unsigned itemSize = _assignment.type()->sizeOnStack();
+		unsigned itemSize = _assignment.annotation().type->sizeOnStack();
 		if (lvalueSize > 0)
 		{
 			utils().copyToStackTop(lvalueSize + itemSize, itemSize);
@@ -207,7 +207,7 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 			// value lvalue_ref value lvalue_ref
 		}
 		m_currentLValue->retrieveValue(_assignment.location(), true);
-		appendOrdinaryBinaryOperatorCode(Token::AssignmentToBinaryOp(op), *_assignment.type());
+		appendOrdinaryBinaryOperatorCode(Token::AssignmentToBinaryOp(op), *_assignment.annotation().type);
 		if (lvalueSize > 0)
 		{
 			solAssert(itemSize + lvalueSize <= 16, "Stack too deep, try removing local variables.");
@@ -228,9 +228,9 @@ bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
 	// the operator should know how to convert itself and to which types it applies, so
 	// put this code together with "Type::acceptsBinary/UnaryOperator" into a class that
 	// represents the operator
-	if (_unaryOperation.type()->category() == Type::Category::IntegerConstant)
+	if (_unaryOperation.annotation().type->category() == Type::Category::IntegerConstant)
 	{
-		m_context << _unaryOperation.type()->literalValue(nullptr);
+		m_context << _unaryOperation.annotation().type->literalValue(nullptr);
 		return false;
 	}
 
@@ -259,7 +259,7 @@ bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
 		if (!_unaryOperation.isPrefixOperation())
 		{
 			// store value for later
-			solAssert(_unaryOperation.type()->sizeOnStack() == 1, "Stack size != 1 not implemented.");
+			solAssert(_unaryOperation.annotation().type->sizeOnStack() == 1, "Stack size != 1 not implemented.");
 			m_context << eth::Instruction::DUP1;
 			if (m_currentLValue->sizeOnStack() > 0)
 				for (unsigned i = 1 + m_currentLValue->sizeOnStack(); i > 0; --i)
@@ -275,7 +275,7 @@ bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
 		for (unsigned i = m_currentLValue->sizeOnStack(); i > 0; --i)
 			m_context << eth::swapInstruction(i);
 		m_currentLValue->storeValue(
-			*_unaryOperation.type(), _unaryOperation.location(),
+			*_unaryOperation.annotation().type, _unaryOperation.location(),
 			!_unaryOperation.isPrefixOperation());
 		m_currentLValue.reset();
 		break;
@@ -297,7 +297,8 @@ bool ExpressionCompiler::visit(BinaryOperation const& _binaryOperation)
 	CompilerContext::LocationSetter locationSetter(m_context, _binaryOperation);
 	Expression const& leftExpression = _binaryOperation.leftExpression();
 	Expression const& rightExpression = _binaryOperation.rightExpression();
-	Type const& commonType = _binaryOperation.commonType();
+	solAssert(!!_binaryOperation.annotation().commonType, "");
+	Type const& commonType = *_binaryOperation.annotation().commonType;
 	Token::Value const c_op = _binaryOperation.getOperator();
 
 	if (c_op == Token::And || c_op == Token::Or) // special case: short-circuiting
@@ -312,22 +313,22 @@ bool ExpressionCompiler::visit(BinaryOperation const& _binaryOperation)
 		// for commutative operators, push the literal as late as possible to allow improved optimization
 		auto isLiteral = [](Expression const& _e)
 		{
-			return dynamic_cast<Literal const*>(&_e) || _e.type()->category() == Type::Category::IntegerConstant;
+			return dynamic_cast<Literal const*>(&_e) || _e.annotation().type->category() == Type::Category::IntegerConstant;
 		};
 		bool swap = m_optimize && Token::isCommutativeOp(c_op) && isLiteral(rightExpression) && !isLiteral(leftExpression);
 		if (swap)
 		{
 			leftExpression.accept(*this);
-			utils().convertType(*leftExpression.type(), commonType, cleanupNeeded);
+			utils().convertType(*leftExpression.annotation().type, commonType, cleanupNeeded);
 			rightExpression.accept(*this);
-			utils().convertType(*rightExpression.type(), commonType, cleanupNeeded);
+			utils().convertType(*rightExpression.annotation().type, commonType, cleanupNeeded);
 		}
 		else
 		{
 			rightExpression.accept(*this);
-			utils().convertType(*rightExpression.type(), commonType, cleanupNeeded);
+			utils().convertType(*rightExpression.annotation().type, commonType, cleanupNeeded);
 			leftExpression.accept(*this);
-			utils().convertType(*leftExpression.type(), commonType, cleanupNeeded);
+			utils().convertType(*leftExpression.annotation().type, commonType, cleanupNeeded);
 		}
 		if (Token::isCompareOp(c_op))
 			appendCompareOperatorCode(c_op, commonType);
@@ -343,25 +344,25 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _functionCall);
 	using Location = FunctionType::Location;
-	if (_functionCall.isTypeConversion())
+	if (_functionCall.annotation().isTypeConversion)
 	{
 		solAssert(_functionCall.arguments().size() == 1, "");
 		solAssert(_functionCall.names().empty(), "");
 		Expression const& firstArgument = *_functionCall.arguments().front();
 		firstArgument.accept(*this);
-		utils().convertType(*firstArgument.type(), *_functionCall.type());
+		utils().convertType(*firstArgument.annotation().type, *_functionCall.annotation().type);
 		return false;
 	}
 
 	FunctionTypePointer functionType;
-	if (_functionCall.isStructConstructorCall())
+	if (_functionCall.annotation().isStructConstructorCall)
 	{
-		auto const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().type());
+		auto const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().annotation().type);
 		auto const& structType = dynamic_cast<StructType const&>(*type.actualType());
 		functionType = structType.constructorType();
 	}
 	else
-		functionType = dynamic_pointer_cast<FunctionType const>(_functionCall.expression().type());
+		functionType = dynamic_pointer_cast<FunctionType const>(_functionCall.expression().annotation().type);
 
 	TypePointers const& parameterTypes = functionType->parameterTypes();
 	vector<ASTPointer<Expression const>> const& callArguments = _functionCall.arguments();
@@ -385,9 +386,9 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			solAssert(found, "");
 		}
 
-	if (_functionCall.isStructConstructorCall())
+	if (_functionCall.annotation().isStructConstructorCall)
 	{
-		TypeType const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().type());
+		TypeType const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().annotation().type);
 		auto const& structType = dynamic_cast<StructType const&>(*type.actualType());
 
 		m_context << u256(max(32u, structType.calldataEncodedSize(true)));
@@ -397,7 +398,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 		for (unsigned i = 0; i < arguments.size(); ++i)
 		{
 			arguments[i]->accept(*this);
-			utils().convertType(*arguments[i]->type(), *functionType->parameterTypes()[i]);
+			utils().convertType(*arguments[i]->annotation().type, *functionType->parameterTypes()[i]);
 			utils().storeInMemoryDynamic(*functionType->parameterTypes()[i]);
 		}
 		m_context << eth::Instruction::POP;
@@ -416,7 +417,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			for (unsigned i = 0; i < arguments.size(); ++i)
 			{
 				arguments[i]->accept(*this);
-				utils().convertType(*arguments[i]->type(), *function.parameterTypes()[i]);
+				utils().convertType(*arguments[i]->annotation().type, *function.parameterTypes()[i]);
 			}
 			_functionCall.expression().accept(*this);
 
@@ -449,7 +450,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			for (auto const& arg: arguments)
 			{
 				arg->accept(*this);
-				argumentTypes.push_back(arg->type());
+				argumentTypes.push_back(arg->annotation().type);
 			}
 			ContractDefinition const& contract =
 				dynamic_cast<ContractType const&>(*function.returnParameterTypes().front()).contractDefinition();
@@ -481,7 +482,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			_functionCall.expression().accept(*this);
 
 			arguments.front()->accept(*this);
-			utils().convertType(*arguments.front()->type(), IntegerType(256), true);
+			utils().convertType(*arguments.front()->annotation().type, IntegerType(256), true);
 			// Note that function is not the original function, but the ".gas" function.
 			// Its values of gasSet and valueSet is equal to the original function's though.
 			unsigned stackDepth = (function.gasSet() ? 1 : 0) + (function.valueSet() ? 1 : 0);
@@ -505,7 +506,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			m_context << u256(0); // do not send gas (there still is the stipend)
 			arguments.front()->accept(*this);
 			utils().convertType(
-				*arguments.front()->type(),
+				*arguments.front()->annotation().type,
 				*function.parameterTypes().front(), true
 			);
 			appendExternalFunctionCall(
@@ -525,7 +526,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			break;
 		case Location::Suicide:
 			arguments.front()->accept(*this);
-			utils().convertType(*arguments.front()->type(), *function.parameterTypes().front(), true);
+			utils().convertType(*arguments.front()->annotation().type, *function.parameterTypes().front(), true);
 			m_context << eth::Instruction::SUICIDE;
 			break;
 		case Location::SHA3:
@@ -534,7 +535,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			for (auto const& arg: arguments)
 			{
 				arg->accept(*this);
-				argumentTypes.push_back(arg->type());
+				argumentTypes.push_back(arg->annotation().type);
 			}
 			utils().fetchFreeMemoryPointer();
 			utils().encodeToMemory(argumentTypes, TypePointers(), function.padArguments(), true);
@@ -552,12 +553,12 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			for (unsigned arg = logNumber; arg > 0; --arg)
 			{
 				arguments[arg]->accept(*this);
-				utils().convertType(*arguments[arg]->type(), *function.parameterTypes()[arg], true);
+				utils().convertType(*arguments[arg]->annotation().type, *function.parameterTypes()[arg], true);
 			}
 			arguments.front()->accept(*this);
 			utils().fetchFreeMemoryPointer();
 			utils().encodeToMemory(
-				{arguments.front()->type()},
+				{arguments.front()->annotation().type},
 				{function.parameterTypes().front()},
 				false,
 				true);
@@ -577,7 +578,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 					++numIndexed;
 					arguments[arg - 1]->accept(*this);
 					utils().convertType(
-						*arguments[arg - 1]->type(),
+						*arguments[arg - 1]->annotation().type,
 						*function.parameterTypes()[arg - 1],
 						true
 					);
@@ -596,7 +597,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 				if (!event.parameters()[arg]->isIndexed())
 				{
 					arguments[arg]->accept(*this);
-					nonIndexedArgTypes.push_back(arguments[arg]->type());
+					nonIndexedArgTypes.push_back(arguments[arg]->annotation().type);
 					nonIndexedParamTypes.push_back(function.parameterTypes()[arg]);
 				}
 			utils().fetchFreeMemoryPointer();
@@ -609,7 +610,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 		case Location::BlockHash:
 		{
 			arguments[0]->accept(*this);
-			utils().convertType(*arguments[0]->type(), *function.parameterTypes()[0], true);
+			utils().convertType(*arguments[0]->annotation().type, *function.parameterTypes()[0], true);
 			m_context << eth::Instruction::BLOCKHASH;
 			break;
 		}
@@ -644,24 +645,24 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _memberAccess);
 	ASTString const& member = _memberAccess.memberName();
-	switch (_memberAccess.expression().type()->category())
+	switch (_memberAccess.expression().annotation().type->category())
 	{
 	case Type::Category::Contract:
 	{
 		bool alsoSearchInteger = false;
-		ContractType const& type = dynamic_cast<ContractType const&>(*_memberAccess.expression().type());
+		ContractType const& type = dynamic_cast<ContractType const&>(*_memberAccess.expression().annotation().type);
 		if (type.isSuper())
 		{
-			solAssert(!!_memberAccess.referencedDeclaration(), "Referenced declaration not resolved.");
+			solAssert(!!_memberAccess.annotation().referencedDeclaration, "Referenced declaration not resolved.");
 			m_context << m_context.superFunctionEntryLabel(
-				dynamic_cast<FunctionDefinition const&>(*_memberAccess.referencedDeclaration()),
+				dynamic_cast<FunctionDefinition const&>(*_memberAccess.annotation().referencedDeclaration),
 				type.contractDefinition()
 			).pushTag();
 		}
 		else
 		{
 			// ordinary contract type
-			if (Declaration const* declaration = _memberAccess.referencedDeclaration())
+			if (Declaration const* declaration = _memberAccess.annotation().referencedDeclaration)
 			{
 				u256 identifier;
 				if (auto const* variable = dynamic_cast<VariableDeclaration const*>(declaration))
@@ -684,7 +685,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 		if (member == "balance")
 		{
 			utils().convertType(
-				*_memberAccess.expression().type(),
+				*_memberAccess.expression().annotation().type,
 				IntegerType(0, IntegerType::Modifier::Address),
 				true
 			);
@@ -692,7 +693,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 		}
 		else if ((set<string>{"send", "call", "callcode"}).count(member))
 			utils().convertType(
-				*_memberAccess.expression().type(),
+				*_memberAccess.expression().annotation().type,
 				IntegerType(0, IntegerType::Modifier::Address),
 				true
 			);
@@ -700,7 +701,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid member access to integer."));
 		break;
 	case Type::Category::Function:
-		solAssert(!!_memberAccess.expression().type()->memberType(member),
+		solAssert(!!_memberAccess.expression().annotation().type->memberType(member),
 				 "Invalid member access to function.");
 		break;
 	case Type::Category::Magic:
@@ -735,7 +736,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 		break;
 	case Type::Category::Struct:
 	{
-		StructType const& type = dynamic_cast<StructType const&>(*_memberAccess.expression().type());
+		StructType const& type = dynamic_cast<StructType const&>(*_memberAccess.expression().annotation().type);
 		switch (type.location())
 		{
 		case DataLocation::Storage:
@@ -748,7 +749,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 		case DataLocation::Memory:
 		{
 			m_context << type.memoryOffsetOfMember(member) << eth::Instruction::ADD;
-			setLValue<MemoryItem>(_memberAccess, *_memberAccess.type());
+			setLValue<MemoryItem>(_memberAccess, *_memberAccess.annotation().type);
 			break;
 		}
 		default:
@@ -758,13 +759,13 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 	}
 	case Type::Category::Enum:
 	{
-		EnumType const& type = dynamic_cast<EnumType const&>(*_memberAccess.expression().type());
+		EnumType const& type = dynamic_cast<EnumType const&>(*_memberAccess.expression().annotation().type);
 		m_context << type.memberValue(_memberAccess.memberName());
 		break;
 	}
 	case Type::Category::TypeType:
 	{
-		TypeType const& type = dynamic_cast<TypeType const&>(*_memberAccess.expression().type());
+		TypeType const& type = dynamic_cast<TypeType const&>(*_memberAccess.expression().annotation().type);
 		solAssert(
 			!type.members().membersByName(_memberAccess.memberName()).empty(),
 			"Invalid member access to " + type.toString(false)
@@ -772,12 +773,12 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 
 		if (dynamic_cast<ContractType const*>(type.actualType().get()))
 		{
-			auto const& funType = dynamic_cast<FunctionType const&>(*_memberAccess.type());
+			auto const& funType = dynamic_cast<FunctionType const&>(*_memberAccess.annotation().type);
 			if (funType.location() != FunctionType::Location::Internal)
 				m_context << funType.externalIdentifier();
 			else
 			{
-				auto const* function = dynamic_cast<FunctionDefinition const*>(_memberAccess.referencedDeclaration());
+				auto const* function = dynamic_cast<FunctionDefinition const*>(_memberAccess.annotation().referencedDeclaration);
 				solAssert(!!function, "Function not found in member access");
 				m_context << m_context.functionEntryLabel(*function).pushTag();
 			}
@@ -789,7 +790,7 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 	case Type::Category::Array:
 	{
 		solAssert(member == "length", "Illegal array member.");
-		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().type());
+		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().annotation().type);
 		if (!type.isDynamicallySized())
 		{
 			utils().popStackElement(type);
@@ -820,7 +821,7 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 	CompilerContext::LocationSetter locationSetter(m_context, _indexAccess);
 	_indexAccess.baseExpression().accept(*this);
 
-	Type const& baseType = *_indexAccess.baseExpression().type();
+	Type const& baseType = *_indexAccess.baseExpression().annotation().type;
 
 	if (baseType.category() == Type::Category::Mapping)
 	{
@@ -834,7 +835,7 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 			// stack: base index mem
 			// note: the following operations must not allocate memory!
 			utils().encodeToMemory(
-				TypePointers{_indexAccess.indexExpression()->type()},
+				TypePointers{_indexAccess.indexExpression()->annotation().type},
 				TypePointers{keyType},
 				false,
 				true
@@ -876,7 +877,7 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 				setLValueToStorageItem(_indexAccess);
 			break;
 		case DataLocation::Memory:
-			setLValue<MemoryItem>(_indexAccess, *_indexAccess.type(), !arrayType.isByteArray());
+			setLValue<MemoryItem>(_indexAccess, *_indexAccess.annotation().type, !arrayType.isByteArray());
 			break;
 		case DataLocation::CallData:
 			//@todo if we implement this, the value in calldata has to be added to the base offset
@@ -900,14 +901,14 @@ bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
 void ExpressionCompiler::endVisit(Identifier const& _identifier)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _identifier);
-	Declaration const* declaration = &_identifier.referencedDeclaration();
+	Declaration const* declaration = _identifier.annotation().referencedDeclaration;
 	if (MagicVariableDeclaration const* magicVar = dynamic_cast<MagicVariableDeclaration const*>(declaration))
 	{
-		switch (magicVar->type()->category())
+		switch (magicVar->type(_identifier.annotation().contractScope)->category())
 		{
 		case Type::Category::Contract:
 			// "this" or "super"
-			if (!dynamic_cast<ContractType const&>(*magicVar->type()).isSuper())
+			if (!dynamic_cast<ContractType const&>(*magicVar->type(_identifier.annotation().contractScope)).isSuper())
 				m_context << eth::Instruction::ADDRESS;
 			break;
 		case Type::Category::Integer:
@@ -927,7 +928,7 @@ void ExpressionCompiler::endVisit(Identifier const& _identifier)
 		else
 		{
 			variable->value()->accept(*this);
-			utils().convertType(*variable->value()->type(), *variable->type());
+			utils().convertType(*variable->value()->annotation().type, *variable->annotation().type);
 		}
 	}
 	else if (auto contract = dynamic_cast<ContractDefinition const*>(declaration))
@@ -953,7 +954,7 @@ void ExpressionCompiler::endVisit(Identifier const& _identifier)
 void ExpressionCompiler::endVisit(Literal const& _literal)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _literal);
-	TypePointer type = _literal.type();
+	TypePointer type = _literal.annotation().type;
 	switch (type->category())
 	{
 	case Type::Category::IntegerConstant:
@@ -1141,7 +1142,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
 	bool manualFunctionId =
 		(funKind == FunctionKind::Bare || funKind == FunctionKind::BareCallCode) &&
 		!_arguments.empty() &&
-		_arguments.front()->type()->mobileType()->calldataEncodedSize(false) ==
+		_arguments.front()->annotation().type->mobileType()->calldataEncodedSize(false) ==
 			CompilerUtils::dataStartOffset;
 	if (manualFunctionId)
 	{
@@ -1149,7 +1150,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
 		// function identifier.
 		_arguments.front()->accept(*this);
 		utils().convertType(
-			*_arguments.front()->type(),
+			*_arguments.front()->annotation().type,
 			IntegerType(8 * CompilerUtils::dataStartOffset),
 			true
 		);
@@ -1161,7 +1162,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
 	for (size_t i = manualFunctionId ? 1 : 0; i < _arguments.size(); ++i)
 	{
 		_arguments[i]->accept(*this);
-		argumentTypes.push_back(_arguments[i]->type());
+		argumentTypes.push_back(_arguments[i]->annotation().type);
 	}
 
 	// Copy function identifier to memory.
@@ -1266,7 +1267,7 @@ void ExpressionCompiler::appendExpressionCopyToMemory(Type const& _expectedType,
 {
 	solAssert(_expectedType.isValueType(), "Not implemented for non-value types.");
 	_expression.accept(*this);
-	utils().convertType(*_expression.type(), _expectedType, true);
+	utils().convertType(*_expression.annotation().type, _expectedType, true);
 	utils().storeInMemoryDynamic(_expectedType);
 }
 
@@ -1284,7 +1285,7 @@ void ExpressionCompiler::setLValueFromDeclaration(Declaration const& _declaratio
 
 void ExpressionCompiler::setLValueToStorageItem(Expression const& _expression)
 {
-	setLValue<StorageItem>(_expression, *_expression.type());
+	setLValue<StorageItem>(_expression, *_expression.annotation().type);
 }
 
 CompilerUtils ExpressionCompiler::utils()
diff --git a/libsolidity/ExpressionCompiler.h b/libsolidity/ExpressionCompiler.h
index 02df4b87..d8fef5af 100644
--- a/libsolidity/ExpressionCompiler.h
+++ b/libsolidity/ExpressionCompiler.h
@@ -127,7 +127,7 @@ void ExpressionCompiler::setLValue(Expression const& _expression, _Arguments con
 {
 	solAssert(!m_currentLValue, "Current LValue not reset before trying to set new one.");
 	std::unique_ptr<_LValueType> lvalue(new _LValueType(m_context, _arguments...));
-	if (_expression.lvalueRequested())
+	if (_expression.annotation().lValueRequested)
 		m_currentLValue = move(lvalue);
 	else
 		lvalue->retrieveValue(_expression.location(), true);
diff --git a/libsolidity/InterfaceHandler.cpp b/libsolidity/InterfaceHandler.cpp
index fc79b493..50006caf 100644
--- a/libsolidity/InterfaceHandler.cpp
+++ b/libsolidity/InterfaceHandler.cpp
@@ -96,7 +96,7 @@ string InterfaceHandler::abiInterface(ContractDefinition const& _contractDef)
 		{
 			Json::Value input;
 			input["name"] = p->name();
-			input["type"] = p->type()->toString(true);
+			input["type"] = p->annotation().type->toString(true);
 			input["indexed"] = p->isIndexed();
 			params.append(input);
 		}
diff --git a/libsolidity/LValue.cpp b/libsolidity/LValue.cpp
index eb7cc073..4bd38b49 100644
--- a/libsolidity/LValue.cpp
+++ b/libsolidity/LValue.cpp
@@ -32,7 +32,7 @@ using namespace solidity;
 
 
 StackVariable::StackVariable(CompilerContext& _compilerContext, Declaration const& _declaration):
-	LValue(_compilerContext, *_declaration.type()),
+	LValue(_compilerContext, *_declaration.annotation().type),
 	m_baseStackOffset(m_context.baseStackOffsetOfVariable(_declaration)),
 	m_size(m_dataType.sizeOnStack())
 {
@@ -132,7 +132,7 @@ void MemoryItem::setToZero(SourceLocation const&, bool _removeReference) const
 }
 
 StorageItem::StorageItem(CompilerContext& _compilerContext, Declaration const& _declaration):
-	StorageItem(_compilerContext, *_declaration.type())
+	StorageItem(_compilerContext, *_declaration.annotation().type)
 {
 	auto const& location = m_context.storageLocationOfVariable(_declaration);
 	m_context << location.first << u256(location.second);
diff --git a/libsolidity/NameAndTypeResolver.cpp b/libsolidity/NameAndTypeResolver.cpp
index c3b49abd..c3e31728 100644
--- a/libsolidity/NameAndTypeResolver.cpp
+++ b/libsolidity/NameAndTypeResolver.cpp
@@ -22,6 +22,7 @@
 
 #include <libsolidity/NameAndTypeResolver.h>
 #include <libsolidity/AST.h>
+#include <libsolidity/TypeChecker.h>
 #include <libsolidity/Exceptions.h>
 
 using namespace std;
@@ -31,7 +32,9 @@ namespace dev
 namespace solidity
 {
 
-NameAndTypeResolver::NameAndTypeResolver(vector<Declaration const*> const& _globals)
+NameAndTypeResolver::NameAndTypeResolver(
+	vector<Declaration const*> const& _globals
+)
 {
 	for (Declaration const* declaration: _globals)
 		m_scopes[nullptr].registerDeclaration(*declaration);
@@ -54,8 +57,8 @@ void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 
 	linearizeBaseContracts(_contract);
 	std::vector<ContractDefinition const*> properBases(
-		++_contract.linearizedBaseContracts().begin(),
-		_contract.linearizedBaseContracts().end()
+		++_contract.annotation().linearizedBaseContracts.begin(),
+		_contract.annotation().linearizedBaseContracts.end()
 	);
 
 	for (ContractDefinition const* base: properBases)
@@ -108,13 +111,6 @@ void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 	}
 }
 
-void NameAndTypeResolver::checkTypeRequirements(ContractDefinition& _contract)
-{
-	for (ASTPointer<StructDefinition> const& structDef: _contract.definedStructs())
-		structDef->checkValidityOfMembers();
-	_contract.checkTypeRequirements();
-}
-
 void NameAndTypeResolver::updateDeclaration(Declaration const& _declaration)
 {
 	m_scopes[nullptr].registerDeclaration(_declaration, false, true);
@@ -187,23 +183,23 @@ void NameAndTypeResolver::linearizeBaseContracts(ContractDefinition& _contract)
 	list<list<ContractDefinition const*>> input(1, {});
 	for (ASTPointer<InheritanceSpecifier> const& baseSpecifier: _contract.baseContracts())
 	{
-		ASTPointer<Identifier> baseName = baseSpecifier->name();
-		auto base = dynamic_cast<ContractDefinition const*>(&baseName->referencedDeclaration());
+		Identifier const& baseName = baseSpecifier->name();
+		auto base = dynamic_cast<ContractDefinition const*>(baseName.annotation().referencedDeclaration);
 		if (!base)
-			BOOST_THROW_EXCEPTION(baseName->createTypeError("Contract expected."));
+			BOOST_THROW_EXCEPTION(baseName.createTypeError("Contract expected."));
 		// "push_front" has the effect that bases mentioned later can overwrite members of bases
 		// mentioned earlier
 		input.back().push_front(base);
-		vector<ContractDefinition const*> const& basesBases = base->linearizedBaseContracts();
+		vector<ContractDefinition const*> const& basesBases = base->annotation().linearizedBaseContracts;
 		if (basesBases.empty())
-			BOOST_THROW_EXCEPTION(baseName->createTypeError("Definition of base has to precede definition of derived contract"));
+			BOOST_THROW_EXCEPTION(baseName.createTypeError("Definition of base has to precede definition of derived contract"));
 		input.push_front(list<ContractDefinition const*>(basesBases.begin(), basesBases.end()));
 	}
 	input.back().push_front(&_contract);
 	vector<ContractDefinition const*> result = cThreeMerge(input);
 	if (result.empty())
 		BOOST_THROW_EXCEPTION(_contract.createTypeError("Linearization of inheritance graph impossible"));
-	_contract.setLinearizedBaseContracts(result);
+	_contract.annotation().linearizedBaseContracts = result;
 }
 
 template <class _T>
@@ -404,139 +400,5 @@ void DeclarationRegistrationHelper::registerDeclaration(Declaration& _declaratio
 		enterNewSubScope(_declaration);
 }
 
-ReferencesResolver::ReferencesResolver(
-	ASTNode& _root,
-	NameAndTypeResolver& _resolver,
-	ContractDefinition const* _currentContract,
-	ParameterList const* _returnParameters,
-	bool _resolveInsideCode,
-	bool _allowLazyTypes
-):
-	m_resolver(_resolver),
-	m_currentContract(_currentContract),
-	m_returnParameters(_returnParameters),
-	m_resolveInsideCode(_resolveInsideCode),
-	m_allowLazyTypes(_allowLazyTypes)
-{
-	_root.accept(*this);
-}
-
-void ReferencesResolver::endVisit(VariableDeclaration& _variable)
-{
-	// endVisit because the internal type needs resolving if it is a user defined type
-	// or mapping
-	if (_variable.typeName())
-	{
-		TypePointer type = _variable.typeName()->toType();
-		using Location = VariableDeclaration::Location;
-		Location loc = _variable.referenceLocation();
-		// References are forced to calldata for external function parameters (not return)
-		// and memory for parameters (also return) of publicly visible functions.
-		// They default to memory for function parameters and storage for local variables.
-		if (auto ref = dynamic_cast<ReferenceType const*>(type.get()))
-		{
-			if (_variable.isExternalCallableParameter())
-			{
-				// force location of external function parameters (not return) to calldata
-				if (loc != Location::Default)
-					BOOST_THROW_EXCEPTION(_variable.createTypeError(
-						"Location has to be calldata for external functions "
-						"(remove the \"memory\" or \"storage\" keyword)."
-					));
-				type = ref->copyForLocation(DataLocation::CallData, true);
-			}
-			else if (_variable.isCallableParameter() && _variable.scope()->isPublic())
-			{
-				// force locations of public or external function (return) parameters to memory
-				if (loc == VariableDeclaration::Location::Storage)
-					BOOST_THROW_EXCEPTION(_variable.createTypeError(
-						"Location has to be memory for publicly visible functions "
-						"(remove the \"storage\" keyword)."
-					));
-				type = ref->copyForLocation(DataLocation::Memory, true);
-			}
-			else
-			{
-				if (_variable.isConstant())
-				{
-					if (loc != Location::Default && loc != Location::Memory)
-						BOOST_THROW_EXCEPTION(_variable.createTypeError(
-							"Storage location has to be \"memory\" (or unspecified) for constants."
-						));
-					loc = Location::Memory;
-				}
-				if (loc == Location::Default)
-					loc = _variable.isCallableParameter() ? Location::Memory : Location::Storage;
-				bool isPointer = !_variable.isStateVariable();
-				type = ref->copyForLocation(
-					loc == Location::Memory ?
-					DataLocation::Memory :
-					DataLocation::Storage,
-					isPointer
-				);
-			}
-		}
-		else if (loc != Location::Default && !ref)
-			BOOST_THROW_EXCEPTION(_variable.createTypeError(
-				"Storage location can only be given for array or struct types."
-			));
-
-		_variable.setType(type);
-
-		if (!_variable.type())
-			BOOST_THROW_EXCEPTION(_variable.typeName()->createTypeError("Invalid type name"));
-	}
-	else if (!m_allowLazyTypes)
-		BOOST_THROW_EXCEPTION(_variable.createTypeError("Explicit type needed."));
-	// otherwise we have a "var"-declaration whose type is resolved by the first assignment
-}
-
-bool ReferencesResolver::visit(Return& _return)
-{
-	_return.setFunctionReturnParameters(m_returnParameters);
-	return true;
-}
-
-bool ReferencesResolver::visit(Mapping&)
-{
-	return true;
-}
-
-bool ReferencesResolver::visit(UserDefinedTypeName& _typeName)
-{
-	auto declarations = m_resolver.nameFromCurrentScope(_typeName.name());
-	if (declarations.empty())
-		BOOST_THROW_EXCEPTION(
-			DeclarationError() <<
-			errinfo_sourceLocation(_typeName.location()) <<
-			errinfo_comment("Undeclared identifier.")
-		);
-	else if (declarations.size() > 1)
-		BOOST_THROW_EXCEPTION(
-			DeclarationError() <<
-			errinfo_sourceLocation(_typeName.location()) <<
-			errinfo_comment("Duplicate identifier.")
-		);
-	else
-		_typeName.setReferencedDeclaration(**declarations.begin());
-	return false;
-}
-
-bool ReferencesResolver::visit(Identifier& _identifier)
-{
-	auto declarations = m_resolver.nameFromCurrentScope(_identifier.name());
-	if (declarations.empty())
-		BOOST_THROW_EXCEPTION(
-			DeclarationError() <<
-			errinfo_sourceLocation(_identifier.location()) <<
-			errinfo_comment("Undeclared identifier.")
-		);
-	else if (declarations.size() == 1)
-		_identifier.setReferencedDeclaration(*declarations.front(), m_currentContract);
-	else
-		_identifier.setOverloadedDeclarations(m_resolver.cleanedDeclarations(_identifier, declarations));
-	return false;
-}
-
 }
 }
diff --git a/libsolidity/NameAndTypeResolver.h b/libsolidity/NameAndTypeResolver.h
index 101787ea..d28671ed 100644
--- a/libsolidity/NameAndTypeResolver.h
+++ b/libsolidity/NameAndTypeResolver.h
@@ -25,9 +25,10 @@
 #include <map>
 #include <list>
 #include <boost/noncopyable.hpp>
-
 #include <libsolidity/DeclarationContainer.h>
+#include <libsolidity/ReferencesResolver.h>
 #include <libsolidity/ASTVisitor.h>
+#include <libsolidity/ASTAnnotations.h>
 
 namespace dev
 {
@@ -42,13 +43,11 @@ namespace solidity
 class NameAndTypeResolver: private boost::noncopyable
 {
 public:
-	explicit NameAndTypeResolver(std::vector<Declaration const*> const& _globals);
+	NameAndTypeResolver(std::vector<Declaration const*> const& _globals);
 	/// Registers all declarations found in the source unit.
 	void registerDeclarations(SourceUnit& _sourceUnit);
 	/// Resolves all names and types referenced from the given contract.
 	void resolveNamesAndTypes(ContractDefinition& _contract);
-	/// Check all type requirements in the given contract.
-	void checkTypeRequirements(ContractDefinition& _contract);
 	/// Updates the given global declaration (used for "this"). Not to be used with declarations
 	/// that create their own scope.
 	void updateDeclaration(Declaration const& _declaration);
@@ -125,36 +124,5 @@ private:
 	VariableScope* m_currentFunction;
 };
 
-/**
- * Resolves references to declarations (of variables and types) and also establishes the link
- * between a return statement and the return parameter list.
- */
-class ReferencesResolver: private ASTVisitor
-{
-public:
-	ReferencesResolver(
-		ASTNode& _root,
-		NameAndTypeResolver& _resolver,
-		ContractDefinition const* _currentContract,
-		ParameterList const* _returnParameters,
-		bool _resolveInsideCode = false,
-		bool _allowLazyTypes = true
-	);
-
-private:
-	virtual void endVisit(VariableDeclaration& _variable) override;
-	virtual bool visit(Block&) override { return m_resolveInsideCode; }
-	virtual bool visit(Identifier& _identifier) override;
-	virtual bool visit(UserDefinedTypeName& _typeName) override;
-	virtual bool visit(Mapping&) override;
-	virtual bool visit(Return& _return) override;
-
-	NameAndTypeResolver& m_resolver;
-	ContractDefinition const* m_currentContract;
-	ParameterList const* m_returnParameters;
-	bool m_resolveInsideCode;
-	bool m_allowLazyTypes;
-};
-
 }
 }
diff --git a/libsolidity/ReferencesResolver.cpp b/libsolidity/ReferencesResolver.cpp
new file mode 100644
index 00000000..b2cdacc4
--- /dev/null
+++ b/libsolidity/ReferencesResolver.cpp
@@ -0,0 +1,225 @@
+/*
+    This file is part of cpp-ethereum.
+
+    cpp-ethereum 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.
+
+    cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Component that resolves type names to types and annotates the AST accordingly.
+ */
+
+#include <libsolidity/ReferencesResolver.h>
+#include <libsolidity/AST.h>
+#include <libsolidity/NameAndTypeResolver.h>
+#include <libsolidity/Exceptions.h>
+#include <libsolidity/ConstantEvaluator.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
+
+ReferencesResolver::ReferencesResolver(
+	ASTNode& _root,
+	NameAndTypeResolver& _resolver,
+	ContractDefinition const* _currentContract,
+	ParameterList const* _returnParameters,
+	bool _resolveInsideCode
+):
+	m_resolver(_resolver),
+	m_currentContract(_currentContract),
+	m_returnParameters(_returnParameters),
+	m_resolveInsideCode(_resolveInsideCode)
+{
+	_root.accept(*this);
+}
+
+bool ReferencesResolver::visit(Return const& _return)
+{
+	_return.annotation().functionReturnParameters = m_returnParameters;
+	return true;
+}
+
+bool ReferencesResolver::visit(UserDefinedTypeName const& _typeName)
+{
+	auto declarations = m_resolver.nameFromCurrentScope(_typeName.name());
+	if (declarations.empty())
+		BOOST_THROW_EXCEPTION(
+			DeclarationError() <<
+			errinfo_sourceLocation(_typeName.location()) <<
+			errinfo_comment("Undeclared identifier.")
+		);
+	else if (declarations.size() > 1)
+		BOOST_THROW_EXCEPTION(
+			DeclarationError() <<
+			errinfo_sourceLocation(_typeName.location()) <<
+			errinfo_comment("Duplicate identifier.")
+		);
+	Declaration const* declaration = *declarations.begin();
+	_typeName.annotation().referencedDeclaration = declaration;
+	return true;
+}
+
+bool ReferencesResolver::visit(Identifier const& _identifier)
+{
+	auto declarations = m_resolver.nameFromCurrentScope(_identifier.name());
+	if (declarations.empty())
+		BOOST_THROW_EXCEPTION(
+			DeclarationError() <<
+			errinfo_sourceLocation(_identifier.location()) <<
+			errinfo_comment("Undeclared identifier.")
+		);
+	else if (declarations.size() == 1)
+	{
+		_identifier.annotation().referencedDeclaration = declarations.front();
+		_identifier.annotation().contractScope = m_currentContract;
+	}
+	else
+		_identifier.annotation().overloadedDeclarations =
+			m_resolver.cleanedDeclarations(_identifier, declarations);
+	return false;
+}
+
+void ReferencesResolver::endVisit(VariableDeclaration const& _variable)
+{
+	if (_variable.annotation().type)
+		return;
+
+	TypePointer type;
+	if (_variable.typeName())
+	{
+		type = typeFor(*_variable.typeName());
+		using Location = VariableDeclaration::Location;
+		Location loc = _variable.referenceLocation();
+		// References are forced to calldata for external function parameters (not return)
+		// and memory for parameters (also return) of publicly visible functions.
+		// They default to memory for function parameters and storage for local variables.
+		if (auto ref = dynamic_cast<ReferenceType const*>(type.get()))
+		{
+			if (_variable.isExternalCallableParameter())
+			{
+				// force location of external function parameters (not return) to calldata
+				if (loc != Location::Default)
+					BOOST_THROW_EXCEPTION(_variable.createTypeError(
+						"Location has to be calldata for external functions "
+						"(remove the \"memory\" or \"storage\" keyword)."
+					));
+				type = ref->copyForLocation(DataLocation::CallData, true);
+			}
+			else if (_variable.isCallableParameter() && _variable.scope()->isPublic())
+			{
+				// force locations of public or external function (return) parameters to memory
+				if (loc == VariableDeclaration::Location::Storage)
+					BOOST_THROW_EXCEPTION(_variable.createTypeError(
+						"Location has to be memory for publicly visible functions "
+						"(remove the \"storage\" keyword)."
+					));
+				type = ref->copyForLocation(DataLocation::Memory, true);
+			}
+			else
+			{
+				if (_variable.isConstant())
+				{
+					if (loc != Location::Default && loc != Location::Memory)
+						BOOST_THROW_EXCEPTION(_variable.createTypeError(
+							"Storage location has to be \"memory\" (or unspecified) for constants."
+						));
+					loc = Location::Memory;
+				}
+				if (loc == Location::Default)
+					loc = _variable.isCallableParameter() ? Location::Memory : Location::Storage;
+				bool isPointer = !_variable.isStateVariable();
+				type = ref->copyForLocation(
+					loc == Location::Memory ?
+					DataLocation::Memory :
+					DataLocation::Storage,
+					isPointer
+				);
+			}
+		}
+		else if (loc != Location::Default && !ref)
+			BOOST_THROW_EXCEPTION(_variable.createTypeError(
+				"Storage location can only be given for array or struct types."
+			));
+
+		if (!type)
+			BOOST_THROW_EXCEPTION(_variable.typeName()->createTypeError("Invalid type name."));
+
+	}
+	else if (!_variable.canHaveAutoType())
+		BOOST_THROW_EXCEPTION(_variable.createTypeError("Explicit type needed."));
+	// otherwise we have a "var"-declaration whose type is resolved by the first assignment
+
+	_variable.annotation().type = type;
+}
+
+TypePointer ReferencesResolver::typeFor(TypeName const& _typeName)
+{
+	if (_typeName.annotation().type)
+		return _typeName.annotation().type;
+
+	TypePointer type;
+	if (auto elemTypeName = dynamic_cast<ElementaryTypeName const*>(&_typeName))
+		type = Type::fromElementaryTypeName(elemTypeName->typeName());
+	else if (dynamic_cast<UserDefinedTypeName const*>(&_typeName))
+	{
+		Declaration const* declaration = _typeName.annotation().referencedDeclaration;
+		solAssert(!!declaration, "");
+
+		if (StructDefinition const* structDef = dynamic_cast<StructDefinition const*>(declaration))
+			type = make_shared<StructType>(*structDef);
+		else if (EnumDefinition const* enumDef = dynamic_cast<EnumDefinition const*>(declaration))
+			type = make_shared<EnumType>(*enumDef);
+		else if (ContractDefinition const* contract = dynamic_cast<ContractDefinition const*>(declaration))
+			type = make_shared<ContractType>(*contract);
+		else
+			BOOST_THROW_EXCEPTION(_typeName.createTypeError(
+				"Name has to refer to a struct, enum or contract."
+			));
+	}
+	else if (auto mapping = dynamic_cast<Mapping const*>(&_typeName))
+	{
+		TypePointer keyType = typeFor(mapping->keyType());
+		TypePointer valueType = typeFor(mapping->valueType());
+		// Convert key type to memory.
+		keyType = ReferenceType::copyForLocationIfReference(DataLocation::Memory, keyType);
+		// Convert value type to storage reference.
+		valueType = ReferenceType::copyForLocationIfReference(DataLocation::Storage, valueType);
+		type = make_shared<MappingType>(keyType, valueType);
+	}
+	else if (auto arrayType = dynamic_cast<ArrayTypeName const*>(&_typeName))
+	{
+		TypePointer baseType = typeFor(arrayType->baseType());
+		if (baseType->storageBytes() == 0)
+			BOOST_THROW_EXCEPTION(arrayType->baseType().createTypeError(
+				"Illegal base type of storage size zero for array."
+			));
+		if (Expression const* length = arrayType->length())
+		{
+			if (!length->annotation().type)
+				ConstantEvaluator e(*length);
+
+			auto const* lengthType = dynamic_cast<IntegerConstantType const*>(length->annotation().type.get());
+			if (!lengthType)
+				BOOST_THROW_EXCEPTION(length->createTypeError("Invalid array length."));
+			type = make_shared<ArrayType>(DataLocation::Storage, baseType, lengthType->literalValue(nullptr));
+		}
+		else
+			type = make_shared<ArrayType>(DataLocation::Storage, baseType);
+	}
+
+	return _typeName.annotation().type = move(type);
+}
+
diff --git a/libsolidity/ReferencesResolver.h b/libsolidity/ReferencesResolver.h
new file mode 100644
index 00000000..b8a55dc2
--- /dev/null
+++ b/libsolidity/ReferencesResolver.h
@@ -0,0 +1,69 @@
+/*
+    This file is part of cpp-ethereum.
+
+    cpp-ethereum 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.
+
+    cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2014
+ * Component that resolves type names to types and annotates the AST accordingly.
+ */
+
+#pragma once
+
+#include <map>
+#include <list>
+#include <boost/noncopyable.hpp>
+#include <libsolidity/ASTVisitor.h>
+#include <libsolidity/ASTAnnotations.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+class NameAndTypeResolver;
+
+/**
+ * Resolves references to declarations (of variables and types) and also establishes the link
+ * between a return statement and the return parameter list.
+ */
+class ReferencesResolver: private ASTConstVisitor
+{
+public:
+	ReferencesResolver(
+		ASTNode& _root,
+		NameAndTypeResolver& _resolver,
+		ContractDefinition const* _currentContract,
+		ParameterList const* _returnParameters,
+		bool _resolveInsideCode = false
+	);
+
+private:
+	virtual bool visit(Block const&) override { return m_resolveInsideCode; }
+	virtual bool visit(Identifier const& _identifier) override;
+	virtual bool visit(UserDefinedTypeName const& _typeName) override;
+	virtual bool visit(Return const& _return) override;
+	virtual void endVisit(VariableDeclaration const& _variable) override;
+
+	TypePointer typeFor(TypeName const& _typeName);
+
+	NameAndTypeResolver& m_resolver;
+	ContractDefinition const* m_currentContract;
+	ParameterList const* m_returnParameters;
+	bool m_resolveInsideCode;
+};
+
+}
+}
diff --git a/libsolidity/TypeChecker.cpp b/libsolidity/TypeChecker.cpp
new file mode 100644
index 00000000..1bb1381b
--- /dev/null
+++ b/libsolidity/TypeChecker.cpp
@@ -0,0 +1,1147 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Type analyzer and checker.
+ */
+
+#include <libsolidity/TypeChecker.h>
+#include <memory>
+#include <boost/range/adaptor/reversed.hpp>
+#include <libsolidity/AST.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
+
+bool TypeChecker::checkTypeRequirements(const ContractDefinition& _contract)
+{
+	try
+	{
+		visit(_contract);
+	}
+	catch (FatalError const&)
+	{
+		// We got a fatal error which required to stop further type checking, but we can
+		// continue normally from here.
+		if (m_errors.empty())
+			throw; // Something is weird here, rather throw again.
+	}
+
+	return m_errors.empty();
+}
+
+TypePointer const& TypeChecker::type(Expression const& _expression) const
+{
+	solAssert(!!_expression.annotation().type, "Type requested but not present.");
+	return _expression.annotation().type;
+}
+
+TypePointer const& TypeChecker::type(VariableDeclaration const& _variable) const
+{
+	solAssert(!!_variable.annotation().type, "Type requested but not present.");
+	return _variable.annotation().type;
+}
+
+bool TypeChecker::visit(ContractDefinition const& _contract)
+{
+	// We force our own visiting order here.
+	ASTNode::listAccept(_contract.definedStructs(), *this);
+	ASTNode::listAccept(_contract.baseContracts(), *this);
+
+	checkContractDuplicateFunctions(_contract);
+	checkContractIllegalOverrides(_contract);
+	checkContractAbstractFunctions(_contract);
+	checkContractAbstractConstructors(_contract);
+
+	FunctionDefinition const* function = _contract.constructor();
+	if (function && !function->returnParameters().empty())
+		typeError(*function->returnParameterList(), "Non-empty \"returns\" directive for constructor.");
+
+	FunctionDefinition const* fallbackFunction = nullptr;
+	for (ASTPointer<FunctionDefinition> const& function: _contract.definedFunctions())
+	{
+		if (function->name().empty())
+		{
+			if (fallbackFunction)
+			{
+				auto err = make_shared<DeclarationError>();
+				*err << errinfo_comment("Only one fallback function is allowed.");
+				m_errors.push_back(move(err));
+			}
+			else
+			{
+				fallbackFunction = function.get();
+				if (!fallbackFunction->parameters().empty())
+					typeError(fallbackFunction->parameterList(), "Fallback function cannot take parameters.");
+			}
+		}
+		if (!function->isImplemented())
+			_contract.annotation().isFullyImplemented = false;
+	}
+
+	ASTNode::listAccept(_contract.stateVariables(), *this);
+	ASTNode::listAccept(_contract.events(), *this);
+	ASTNode::listAccept(_contract.functionModifiers(), *this);
+	ASTNode::listAccept(_contract.definedFunctions(), *this);
+
+	checkContractExternalTypeClashes(_contract);
+	// check for hash collisions in function signatures
+	set<FixedHash<4>> hashes;
+	for (auto const& it: _contract.interfaceFunctionList())
+	{
+		FixedHash<4> const& hash = it.first;
+		if (hashes.count(hash))
+			typeError(
+				_contract,
+				string("Function signature hash collision for ") + it.second->externalSignature()
+			);
+		hashes.insert(hash);
+	}
+
+	if (_contract.isLibrary())
+		checkLibraryRequirements(_contract);
+
+	return false;
+}
+
+void TypeChecker::checkContractDuplicateFunctions(ContractDefinition const& _contract)
+{
+	/// Checks that two functions with the same name defined in this contract have different
+	/// argument types and that there is at most one constructor.
+	map<string, vector<FunctionDefinition const*>> functions;
+	for (ASTPointer<FunctionDefinition> const& function: _contract.definedFunctions())
+		functions[function->name()].push_back(function.get());
+
+	// Constructor
+	if (functions[_contract.name()].size() > 1)
+	{
+		SecondarySourceLocation ssl;
+		auto it = ++functions[_contract.name()].begin();
+		for (; it != functions[_contract.name()].end(); ++it)
+			ssl.append("Another declaration is here:", (*it)->location());
+
+		auto err = make_shared<DeclarationError>();
+		*err <<
+			errinfo_sourceLocation(functions[_contract.name()].front()->location()) <<
+			errinfo_comment("More than one constructor defined.") <<
+			errinfo_secondarySourceLocation(ssl);
+		m_errors.push_back(move(err));
+	}
+	for (auto const& it: functions)
+	{
+		vector<FunctionDefinition const*> const& overloads = it.second;
+		for (size_t i = 0; i < overloads.size(); ++i)
+			for (size_t j = i + 1; j < overloads.size(); ++j)
+				if (FunctionType(*overloads[i]).hasEqualArgumentTypes(FunctionType(*overloads[j])))
+				{
+					auto err = make_shared<DeclarationError>();
+					*err <<
+						errinfo_sourceLocation(overloads[j]->location()) <<
+						errinfo_comment("Function with same name and arguments defined twice.") <<
+						errinfo_secondarySourceLocation(SecondarySourceLocation().append(
+							"Other declaration is here:", overloads[i]->location()));
+					m_errors.push_back(move(err));
+				}
+	}
+}
+
+void TypeChecker::checkContractAbstractFunctions(ContractDefinition const& _contract)
+{
+	// Mapping from name to function definition (exactly one per argument type equality class) and
+	// flag to indicate whether it is fully implemented.
+	using FunTypeAndFlag = std::pair<FunctionTypePointer, bool>;
+	map<string, vector<FunTypeAndFlag>> functions;
+
+	// Search from base to derived
+	for (ContractDefinition const* contract: boost::adaptors::reverse(_contract.annotation().linearizedBaseContracts))
+		for (ASTPointer<FunctionDefinition> const& function: contract->definedFunctions())
+		{
+			auto& overloads = functions[function->name()];
+			FunctionTypePointer funType = make_shared<FunctionType>(*function);
+			auto it = find_if(overloads.begin(), overloads.end(), [&](FunTypeAndFlag const& _funAndFlag)
+			{
+				return funType->hasEqualArgumentTypes(*_funAndFlag.first);
+			});
+			if (it == overloads.end())
+				overloads.push_back(make_pair(funType, function->isImplemented()));
+			else if (it->second)
+			{
+				if (!function->isImplemented())
+					typeError(*function, "Redeclaring an already implemented function as abstract");
+			}
+			else if (function->isImplemented())
+				it->second = true;
+		}
+
+	// Set to not fully implemented if at least one flag is false.
+	for (auto const& it: functions)
+		for (auto const& funAndFlag: it.second)
+			if (!funAndFlag.second)
+			{
+				_contract.annotation().isFullyImplemented = false;
+				return;
+			}
+}
+
+void TypeChecker::checkContractAbstractConstructors(ContractDefinition const& _contract)
+{
+	set<ContractDefinition const*> argumentsNeeded;
+	// check that we get arguments for all base constructors that need it.
+	// If not mark the contract as abstract (not fully implemented)
+
+	vector<ContractDefinition const*> const& bases = _contract.annotation().linearizedBaseContracts;
+	for (ContractDefinition const* contract: bases)
+		if (FunctionDefinition const* constructor = contract->constructor())
+			if (contract != &_contract && !constructor->parameters().empty())
+				argumentsNeeded.insert(contract);
+
+	for (ContractDefinition const* contract: bases)
+	{
+		if (FunctionDefinition const* constructor = contract->constructor())
+			for (auto const& modifier: constructor->modifiers())
+			{
+				auto baseContract = dynamic_cast<ContractDefinition const*>(
+					&dereference(*modifier->name())
+				);
+				if (baseContract)
+					argumentsNeeded.erase(baseContract);
+			}
+
+
+		for (ASTPointer<InheritanceSpecifier> const& base: contract->baseContracts())
+		{
+			auto baseContract = dynamic_cast<ContractDefinition const*>(&dereference(base->name()));
+			solAssert(baseContract, "");
+			if (!base->arguments().empty())
+				argumentsNeeded.erase(baseContract);
+		}
+	}
+	if (!argumentsNeeded.empty())
+		_contract.annotation().isFullyImplemented = false;
+}
+
+void TypeChecker::checkContractIllegalOverrides(ContractDefinition const& _contract)
+{
+	// TODO unify this at a later point. for this we need to put the constness and the access specifier
+	// into the types
+	map<string, vector<FunctionDefinition const*>> functions;
+	map<string, ModifierDefinition const*> modifiers;
+
+	// We search from derived to base, so the stored item causes the error.
+	for (ContractDefinition const* contract: _contract.annotation().linearizedBaseContracts)
+	{
+		for (ASTPointer<FunctionDefinition> const& function: contract->definedFunctions())
+		{
+			if (function->isConstructor())
+				continue; // constructors can neither be overridden nor override anything
+			string const& name = function->name();
+			if (modifiers.count(name))
+				typeError(*modifiers[name], "Override changes function to modifier.");
+			FunctionType functionType(*function);
+			// function should not change the return type
+			for (FunctionDefinition const* overriding: functions[name])
+			{
+				FunctionType overridingType(*overriding);
+				if (!overridingType.hasEqualArgumentTypes(functionType))
+					continue;
+				if (
+					overriding->visibility() != function->visibility() ||
+					overriding->isDeclaredConst() != function->isDeclaredConst() ||
+					overridingType != functionType
+				)
+					typeError(*overriding, "Override changes extended function signature.");
+			}
+			functions[name].push_back(function.get());
+		}
+		for (ASTPointer<ModifierDefinition> const& modifier: contract->functionModifiers())
+		{
+			string const& name = modifier->name();
+			ModifierDefinition const*& override = modifiers[name];
+			if (!override)
+				override = modifier.get();
+			else if (ModifierType(*override) != ModifierType(*modifier))
+				typeError(*override, "Override changes modifier signature.");
+			if (!functions[name].empty())
+				typeError(*override, "Override changes modifier to function.");
+		}
+	}
+}
+
+void TypeChecker::checkContractExternalTypeClashes(ContractDefinition const& _contract)
+{
+	map<string, vector<pair<Declaration const*, FunctionTypePointer>>> externalDeclarations;
+	for (ContractDefinition const* contract: _contract.annotation().linearizedBaseContracts)
+	{
+		for (ASTPointer<FunctionDefinition> const& f: contract->definedFunctions())
+			if (f->isPartOfExternalInterface())
+			{
+				auto functionType = make_shared<FunctionType>(*f);
+				externalDeclarations[functionType->externalSignature(f->name())].push_back(
+					make_pair(f.get(), functionType)
+				);
+			}
+		for (ASTPointer<VariableDeclaration> const& v: contract->stateVariables())
+			if (v->isPartOfExternalInterface())
+			{
+				auto functionType = make_shared<FunctionType>(*v);
+				externalDeclarations[functionType->externalSignature(v->name())].push_back(
+					make_pair(v.get(), functionType)
+				);
+			}
+	}
+	for (auto const& it: externalDeclarations)
+		for (size_t i = 0; i < it.second.size(); ++i)
+			for (size_t j = i + 1; j < it.second.size(); ++j)
+				if (!it.second[i].second->hasEqualArgumentTypes(*it.second[j].second))
+					typeError(
+						*it.second[j].first,
+						"Function overload clash during conversion to external types for arguments."
+					);
+}
+
+void TypeChecker::checkLibraryRequirements(ContractDefinition const& _contract)
+{
+	solAssert(_contract.isLibrary(), "");
+	if (!_contract.baseContracts().empty())
+		typeError(_contract, "Library is not allowed to inherit.");
+
+	for (auto const& var: _contract.stateVariables())
+		if (!var->isConstant())
+			typeError(*var, "Library cannot have non-constant state variables");
+}
+
+void TypeChecker::endVisit(InheritanceSpecifier const& _inheritance)
+{
+	auto base = dynamic_cast<ContractDefinition const*>(&dereference(_inheritance.name()));
+	solAssert(base, "Base contract not available.");
+
+	if (base->isLibrary())
+		typeError(_inheritance, "Libraries cannot be inherited from.");
+
+	auto const& arguments = _inheritance.arguments();
+	TypePointers parameterTypes = ContractType(*base).constructorType()->parameterTypes();
+	if (!arguments.empty() && parameterTypes.size() != arguments.size())
+		typeError(
+			_inheritance,
+			"Wrong argument count for constructor call: " +
+			toString(arguments.size()) +
+			" arguments given but expected " +
+			toString(parameterTypes.size()) +
+			"."
+		);
+
+	for (size_t i = 0; i < arguments.size(); ++i)
+		if (!type(*arguments[i])->isImplicitlyConvertibleTo(*parameterTypes[i]))
+			typeError(
+				*arguments[i],
+				"Invalid type for argument in constructor call. "
+				"Invalid implicit conversion from " +
+				type(*arguments[i])->toString() +
+				" to " +
+				parameterTypes[i]->toString() +
+				" requested."
+			);
+}
+
+bool TypeChecker::visit(StructDefinition const& _struct)
+{
+	for (ASTPointer<VariableDeclaration> const& member: _struct.members())
+		if (!type(*member)->canBeStored())
+			typeError(*member, "Type cannot be used in struct.");
+
+	// Check recursion, fatal error if detected.
+	using StructPointer = StructDefinition const*;
+	using StructPointersSet = set<StructPointer>;
+	function<void(StructPointer,StructPointersSet const&)> check = [&](StructPointer _struct, StructPointersSet const& _parents)
+	{
+		if (_parents.count(_struct))
+			fatalTypeError(*_struct, "Recursive struct definition.");
+		StructPointersSet parents = _parents;
+		parents.insert(_struct);
+		for (ASTPointer<VariableDeclaration> const& member: _struct->members())
+			if (type(*member)->category() == Type::Category::Struct)
+			{
+				auto const& typeName = dynamic_cast<UserDefinedTypeName const&>(*member->typeName());
+				check(&dynamic_cast<StructDefinition const&>(*typeName.annotation().referencedDeclaration), parents);
+			}
+	};
+	check(&_struct, StructPointersSet{});
+
+	ASTNode::listAccept(_struct.members(), *this);
+
+	return false;
+}
+
+bool TypeChecker::visit(FunctionDefinition const& _function)
+{
+	for (ASTPointer<VariableDeclaration> const& var: _function.parameters() + _function.returnParameters())
+	{
+		if (!type(*var)->canLiveOutsideStorage())
+			typeError(*var, "Type is required to live outside storage.");
+		if (_function.visibility() >= FunctionDefinition::Visibility::Public && !(type(*var)->externalType()))
+			typeError(*var, "Internal type is not allowed for public and external functions.");
+	}
+	for (ASTPointer<ModifierInvocation> const& modifier: _function.modifiers())
+		visitManually(
+			*modifier,
+			_function.isConstructor() ?
+			_function.scope()->annotation().linearizedBaseContracts :
+			vector<ContractDefinition const*>()
+		);
+	if (_function.isImplemented())
+		_function.body().accept(*this);
+	return false;
+}
+
+bool TypeChecker::visit(VariableDeclaration const& _variable)
+{
+	// Variables can be declared without type (with "var"), in which case the first assignment
+	// sets the type.
+	// Note that assignments before the first declaration are legal because of the special scoping
+	// rules inherited from JavaScript.
+
+	// This only infers the type from its type name.
+	// If an explicit type is required, it throws, otherwise it returns TypePointer();
+	TypePointer varType = _variable.annotation().type;
+	if (_variable.isConstant())
+	{
+		if (!dynamic_cast<ContractDefinition const*>(_variable.scope()))
+			typeError(_variable, "Illegal use of \"constant\" specifier.");
+		if (!_variable.value())
+			typeError(_variable, "Uninitialized \"constant\" variable.");
+		if (varType && !varType->isValueType())
+		{
+			bool constImplemented = false;
+			if (auto arrayType = dynamic_cast<ArrayType const*>(varType.get()))
+				constImplemented = arrayType->isByteArray();
+			if (!constImplemented)
+				typeError(
+					_variable,
+					"Illegal use of \"constant\" specifier. \"constant\" "
+					"is not yet implemented for this type."
+				);
+		}
+	}
+	if (varType)
+	{
+		if (_variable.value())
+			expectType(*_variable.value(), *varType);
+	}
+	else
+	{
+		// Infer type from value.
+		if (!_variable.value())
+			fatalTypeError(_variable, "Assignment necessary for type detection.");
+		_variable.value()->accept(*this);
+
+		TypePointer const& valueType = type(*_variable.value());
+		solAssert(!!valueType, "");
+		if (
+			valueType->category() == Type::Category::IntegerConstant &&
+			!dynamic_pointer_cast<IntegerConstantType const>(valueType)->integerType()
+		)
+			fatalTypeError(*_variable.value(), "Invalid integer constant " + valueType->toString() + ".");
+		else if (valueType->category() == Type::Category::Void)
+			fatalTypeError(_variable, "Variable cannot have void type.");
+		varType = valueType->mobileType();
+	}
+	solAssert(!!varType, "");
+	_variable.annotation().type = varType;
+	if (!_variable.isStateVariable())
+	{
+		if (varType->dataStoredIn(DataLocation::Memory) || varType->dataStoredIn(DataLocation::CallData))
+			if (!varType->canLiveOutsideStorage())
+				typeError(_variable, "Type " + varType->toString() + " is only valid in storage.");
+	}
+	else if (
+		_variable.visibility() >= VariableDeclaration::Visibility::Public &&
+		!FunctionType(_variable).externalType()
+	)
+		typeError(_variable, "Internal type is not allowed for public state variables.");
+	return false;
+}
+
+void TypeChecker::visitManually(
+	ModifierInvocation const& _modifier,
+	vector<ContractDefinition const*> const& _bases
+)
+{
+	std::vector<ASTPointer<Expression>> const& arguments = _modifier.arguments();
+	_modifier.annotation().argumentTypes = make_shared<TypePointers>();
+	for (ASTPointer<Expression> const& argument: arguments)
+	{
+		argument->accept(*this);
+		_modifier.annotation().argumentTypes->push_back(type(*argument));
+	}
+	_modifier.name()->accept(*this);
+
+	auto const* declaration = &dereference(*_modifier.name());
+	vector<ASTPointer<VariableDeclaration>> emptyParameterList;
+	vector<ASTPointer<VariableDeclaration>> const* parameters = nullptr;
+	if (auto modifierDecl = dynamic_cast<ModifierDefinition const*>(declaration))
+		parameters = &modifierDecl->parameters();
+	else
+		// check parameters for Base constructors
+		for (ContractDefinition const* base: _bases)
+			if (declaration == base)
+			{
+				if (auto referencedConstructor = base->constructor())
+					parameters = &referencedConstructor->parameters();
+				else
+					parameters = &emptyParameterList;
+				break;
+			}
+	if (!parameters)
+		typeError(_modifier, "Referenced declaration is neither modifier nor base class.");
+	if (parameters->size() != arguments.size())
+		typeError(
+			_modifier,
+			"Wrong argument count for modifier invocation: " +
+			toString(arguments.size()) +
+			" arguments given but expected " +
+			toString(parameters->size()) +
+			"."
+		);
+	for (size_t i = 0; i < _modifier.arguments().size(); ++i)
+		if (!type(*arguments[i])->isImplicitlyConvertibleTo(*type(*(*parameters)[i])))
+			typeError(
+				*arguments[i],
+				"Invalid type for argument in modifier invocation. "
+				"Invalid implicit conversion from " +
+				type(*arguments[i])->toString() +
+				" to " +
+				type(*(*parameters)[i])->toString() +
+				" requested."
+			);
+}
+
+bool TypeChecker::visit(EventDefinition const& _eventDef)
+{
+	unsigned numIndexed = 0;
+	for (ASTPointer<VariableDeclaration> const& var: _eventDef.parameters())
+	{
+		if (var->isIndexed())
+			numIndexed++;
+		if (numIndexed > 3)
+			typeError(_eventDef, "More than 3 indexed arguments for event.");
+		if (!type(*var)->canLiveOutsideStorage())
+			typeError(*var, "Type is required to live outside storage.");
+		if (!type(*var)->externalType())
+			typeError(*var, "Internal type is not allowed as event parameter type.");
+	}
+	return false;
+}
+
+
+bool TypeChecker::visit(IfStatement const& _ifStatement)
+{
+	expectType(_ifStatement.condition(), BoolType());
+	_ifStatement.trueStatement().accept(*this);
+	if (_ifStatement.falseStatement())
+		_ifStatement.falseStatement()->accept(*this);
+	return false;
+}
+
+bool TypeChecker::visit(WhileStatement const& _whileStatement)
+{
+	expectType(_whileStatement.condition(), BoolType());
+	_whileStatement.body().accept(*this);
+	return false;
+}
+
+bool TypeChecker::visit(ForStatement const& _forStatement)
+{
+	if (_forStatement.initializationExpression())
+		_forStatement.initializationExpression()->accept(*this);
+	if (_forStatement.condition())
+		expectType(*_forStatement.condition(), BoolType());
+	if (_forStatement.loopExpression())
+		_forStatement.loopExpression()->accept(*this);
+	_forStatement.body().accept(*this);
+	return false;
+}
+
+void TypeChecker::endVisit(Return const& _return)
+{
+	if (!_return.expression())
+		return;
+	ParameterList const* params = _return.annotation().functionReturnParameters;
+	if (!params)
+		typeError(_return, "Return arguments not allowed.");
+	else if (params->parameters().size() != 1)
+		typeError(_return, "Different number of arguments in return statement than in returns declaration.");
+	else
+	{
+		// this could later be changed such that the paramaters type is an anonymous struct type,
+		// but for now, we only allow one return parameter
+		TypePointer const& expected = type(*params->parameters().front());
+		if (!type(*_return.expression())->isImplicitlyConvertibleTo(*expected))
+			typeError(
+				*_return.expression(),
+				"Return argument type " +
+				type(*_return.expression())->toString() +
+				" is not implicitly convertible to expected type (type of first return variable) " +
+				expected->toString() +
+				"."
+			);
+	}
+}
+
+void TypeChecker::endVisit(ExpressionStatement const& _statement)
+{
+	if (type(_statement.expression())->category() == Type::Category::IntegerConstant)
+		if (!dynamic_pointer_cast<IntegerConstantType const>(type(_statement.expression()))->integerType())
+			typeError(_statement.expression(), "Invalid integer constant.");
+}
+
+bool TypeChecker::visit(Assignment const& _assignment)
+{
+	requireLValue(_assignment.leftHandSide());
+	TypePointer t = type(_assignment.leftHandSide());
+	_assignment.annotation().type = t;
+	if (t->category() == Type::Category::Mapping)
+	{
+		typeError(_assignment, "Mappings cannot be assigned to.");
+		_assignment.rightHandSide().accept(*this);
+	}
+	else if (_assignment.assignmentOperator() == Token::Assign)
+		expectType(_assignment.rightHandSide(), *t);
+	else
+	{
+		// compound assignment
+		_assignment.rightHandSide().accept(*this);
+		TypePointer resultType = t->binaryOperatorResult(
+			Token::AssignmentToBinaryOp(_assignment.assignmentOperator()),
+			type(_assignment.rightHandSide())
+		);
+		if (!resultType || *resultType != *t)
+			typeError(
+				_assignment,
+				"Operator " +
+				string(Token::toString(_assignment.assignmentOperator())) +
+				" not compatible with types " +
+				t->toString() +
+				" and " +
+				type(_assignment.rightHandSide())->toString()
+			);
+	}
+	return false;
+}
+
+bool TypeChecker::visit(UnaryOperation const& _operation)
+{
+	// Inc, Dec, Add, Sub, Not, BitNot, Delete
+	Token::Value op = _operation.getOperator();
+	if (op == Token::Value::Inc || op == Token::Value::Dec || op == Token::Value::Delete)
+		requireLValue(_operation.subExpression());
+	else
+		_operation.subExpression().accept(*this);
+	TypePointer const& subExprType = type(_operation.subExpression());
+	TypePointer t = type(_operation.subExpression())->unaryOperatorResult(op);
+	if (!t)
+	{
+		typeError(
+			_operation,
+			"Unary operator " +
+			string(Token::toString(op)) +
+			" cannot be applied to type " +
+			subExprType->toString()
+		);
+		t = subExprType;
+	}
+	_operation.annotation().type = t;
+	return false;
+}
+
+void TypeChecker::endVisit(BinaryOperation const& _operation)
+{
+	TypePointer const& leftType = type(_operation.leftExpression());
+	TypePointer const& rightType = type(_operation.rightExpression());
+	TypePointer commonType = leftType->binaryOperatorResult(_operation.getOperator(), rightType);
+	if (!commonType)
+	{
+		typeError(
+			_operation,
+			"Operator " +
+			string(Token::toString(_operation.getOperator())) +
+			" not compatible with types " +
+			leftType->toString() +
+			" and " +
+			rightType->toString()
+		);
+		commonType = leftType;
+	}
+	_operation.annotation().commonType = commonType;
+	_operation.annotation().type =
+		Token::isCompareOp(_operation.getOperator()) ?
+		make_shared<BoolType>() :
+		commonType;
+}
+
+bool TypeChecker::visit(FunctionCall const& _functionCall)
+{
+	bool isPositionalCall = _functionCall.names().empty();
+	vector<ASTPointer<Expression const>> arguments = _functionCall.arguments();
+	vector<ASTPointer<ASTString>> const& argumentNames = _functionCall.names();
+
+	// We need to check arguments' type first as they will be needed for overload resolution.
+	shared_ptr<TypePointers> argumentTypes;
+	if (isPositionalCall)
+		argumentTypes = make_shared<TypePointers>();
+	for (ASTPointer<Expression const> const& argument: arguments)
+	{
+		argument->accept(*this);
+		// only store them for positional calls
+		if (isPositionalCall)
+			argumentTypes->push_back(type(*argument));
+	}
+	if (isPositionalCall)
+		_functionCall.expression().annotation().argumentTypes = move(argumentTypes);
+
+	_functionCall.expression().accept(*this);
+	TypePointer expressionType = type(_functionCall.expression());
+
+	if (auto const* typeType = dynamic_cast<TypeType const*>(expressionType.get()))
+	{
+		_functionCall.annotation().isStructConstructorCall = (typeType->actualType()->category() == Type::Category::Struct);
+		_functionCall.annotation().isTypeConversion = !_functionCall.annotation().isStructConstructorCall;
+	}
+	else
+		_functionCall.annotation().isStructConstructorCall = _functionCall.annotation().isTypeConversion = false;
+
+	if (_functionCall.annotation().isTypeConversion)
+	{
+		TypeType const& t = dynamic_cast<TypeType const&>(*expressionType);
+		TypePointer resultType = t.actualType();
+		if (arguments.size() != 1)
+			typeError(_functionCall, "Exactly one argument expected for explicit type conversion.");
+		else if (!isPositionalCall)
+			typeError(_functionCall, "Type conversion cannot allow named arguments.");
+		else
+		{
+			TypePointer const& argType = type(*arguments.front());
+			if (auto argRefType = dynamic_cast<ReferenceType const*>(argType.get()))
+				// do not change the data location when converting
+				// (data location cannot yet be specified for type conversions)
+				resultType = ReferenceType::copyForLocationIfReference(argRefType->location(), resultType);
+			if (!argType->isExplicitlyConvertibleTo(*resultType))
+				typeError(_functionCall, "Explicit type conversion not allowed.");
+		}
+		_functionCall.annotation().type = resultType;
+
+		return false;
+	}
+
+	// Actual function call or struct constructor call.
+
+	FunctionTypePointer functionType;
+
+	/// For error message: Struct members that were removed during conversion to memory.
+	set<string> membersRemovedForStructConstructor;
+	if (_functionCall.annotation().isStructConstructorCall)
+	{
+		TypeType const& t = dynamic_cast<TypeType const&>(*expressionType);
+		auto const& structType = dynamic_cast<StructType const&>(*t.actualType());
+		functionType = structType.constructorType();
+		membersRemovedForStructConstructor = structType.membersMissingInMemory();
+	}
+	else
+		functionType = dynamic_pointer_cast<FunctionType const>(expressionType);
+
+	if (!functionType)
+	{
+		typeError(_functionCall, "Type is not callable");
+		_functionCall.annotation().type = make_shared<VoidType>();
+		return false;
+	}
+	else
+	{
+		// @todo actually the return type should be an anonymous struct,
+		// but we change it to the type of the first return value until we have anonymous
+		// structs and tuples
+		if (functionType->returnParameterTypes().empty())
+			_functionCall.annotation().type = make_shared<VoidType>();
+		else
+			_functionCall.annotation().type = functionType->returnParameterTypes().front();
+	}
+
+	//@todo would be nice to create a struct type from the arguments
+	// and then ask if that is implicitly convertible to the struct represented by the
+	// function parameters
+	TypePointers const& parameterTypes = functionType->parameterTypes();
+	if (!functionType->takesArbitraryParameters() && parameterTypes.size() != arguments.size())
+	{
+		string msg =
+			"Wrong argument count for function call: " +
+			toString(arguments.size()) +
+			" arguments given but expected " +
+			toString(parameterTypes.size()) +
+			".";
+		// Extend error message in case we try to construct a struct with mapping member.
+		if (_functionCall.annotation().isStructConstructorCall && !membersRemovedForStructConstructor.empty())
+		{
+			msg += " Members that have to be skipped in memory:";
+			for (auto const& member: membersRemovedForStructConstructor)
+				msg += " " + member;
+		}
+		typeError(_functionCall, msg);
+	}
+	else if (isPositionalCall)
+	{
+		// call by positional arguments
+		for (size_t i = 0; i < arguments.size(); ++i)
+			if (
+				!functionType->takesArbitraryParameters() &&
+				!type(*arguments[i])->isImplicitlyConvertibleTo(*parameterTypes[i])
+			)
+				typeError(
+					*arguments[i],
+					"Invalid type for argument in function call. "
+					"Invalid implicit conversion from " +
+					type(*arguments[i])->toString() +
+					" to " +
+					parameterTypes[i]->toString() +
+					" requested."
+				);
+	}
+	else
+	{
+		// call by named arguments
+		auto const& parameterNames = functionType->parameterNames();
+		if (functionType->takesArbitraryParameters())
+			typeError(
+				_functionCall,
+				"Named arguments cannnot be used for functions that take arbitrary parameters."
+			);
+		else if (parameterNames.size() > argumentNames.size())
+			typeError(_functionCall, "Some argument names are missing.");
+		else if (parameterNames.size() < argumentNames.size())
+			typeError(_functionCall, "Too many arguments.");
+		else
+		{
+			// check duplicate names
+			bool duplication = false;
+			for (size_t i = 0; i < argumentNames.size(); i++)
+				for (size_t j = i + 1; j < argumentNames.size(); j++)
+					if (*argumentNames[i] == *argumentNames[j])
+					{
+						duplication = true;
+						typeError(*arguments[i], "Duplicate named argument.");
+					}
+
+			// check actual types
+			if (!duplication)
+				for (size_t i = 0; i < argumentNames.size(); i++)
+				{
+					bool found = false;
+					for (size_t j = 0; j < parameterNames.size(); j++)
+						if (parameterNames[j] == *argumentNames[i])
+						{
+							found = true;
+							// check type convertible
+							if (!type(*arguments[i])->isImplicitlyConvertibleTo(*parameterTypes[j]))
+								typeError(
+									*arguments[i],
+									"Invalid type for argument in function call. "
+									"Invalid implicit conversion from " +
+									type(*arguments[i])->toString() +
+									" to " +
+									parameterTypes[i]->toString() +
+									" requested."
+								);
+							break;
+						}
+
+					if (!found)
+						typeError(
+							_functionCall,
+							"Named argument does not match function declaration."
+						);
+				}
+		}
+	}
+
+	return false;
+}
+
+void TypeChecker::endVisit(NewExpression const& _newExpression)
+{
+	auto contract = dynamic_cast<ContractDefinition const*>(&dereference(_newExpression.contractName()));
+
+	if (!contract)
+		fatalTypeError(_newExpression, "Identifier is not a contract.");
+	if (!contract->annotation().isFullyImplemented)
+		typeError(_newExpression, "Trying to create an instance of an abstract contract.");
+
+	auto scopeContract = _newExpression.contractName().annotation().contractScope;
+	auto const& bases = contract->annotation().linearizedBaseContracts;
+	solAssert(!bases.empty(), "Linearized base contracts not yet available.");
+	if (find(bases.begin(), bases.end(), scopeContract) != bases.end())
+		typeError(
+			_newExpression,
+			"Circular reference for contract creation: cannot create instance of derived or same contract."
+		);
+
+	auto contractType = make_shared<ContractType>(*contract);
+	TypePointers const& parameterTypes = contractType->constructorType()->parameterTypes();
+	_newExpression.annotation().type = make_shared<FunctionType>(
+		parameterTypes,
+		TypePointers{contractType},
+		strings(),
+		strings(),
+		FunctionType::Location::Creation
+	);
+}
+
+bool TypeChecker::visit(MemberAccess const& _memberAccess)
+{
+	_memberAccess.expression().accept(*this);
+	TypePointer exprType = type(_memberAccess.expression());
+	ASTString const& memberName = _memberAccess.memberName();
+
+	// Retrieve the types of the arguments if this is used to call a function.
+	auto const& argumentTypes = _memberAccess.annotation().argumentTypes;
+	MemberList::MemberMap possibleMembers = exprType->members().membersByName(memberName);
+	if (possibleMembers.size() > 1 && argumentTypes)
+	{
+		// do overload resolution
+		for (auto it = possibleMembers.begin(); it != possibleMembers.end();)
+			if (
+				it->type->category() == Type::Category::Function &&
+				!dynamic_cast<FunctionType const&>(*it->type).canTakeArguments(*argumentTypes)
+			)
+				it = possibleMembers.erase(it);
+			else
+				++it;
+	}
+	if (possibleMembers.size() == 0)
+	{
+		auto storageType = ReferenceType::copyForLocationIfReference(
+			DataLocation::Storage,
+			exprType
+		);
+		if (!storageType->members().membersByName(memberName).empty())
+			fatalTypeError(
+				_memberAccess,
+				"Member \"" + memberName + "\" is not available in " +
+				exprType->toString() +
+				" outside of storage."
+			);
+		fatalTypeError(
+			_memberAccess,
+			"Member \"" + memberName + "\" not found or not visible "
+			"after argument-dependent lookup in " + exprType->toString()
+		);
+	}
+	else if (possibleMembers.size() > 1)
+		fatalTypeError(
+			_memberAccess,
+			"Member \"" + memberName + "\" not unique "
+			"after argument-dependent lookup in " + exprType->toString()
+		);
+
+	auto& annotation = _memberAccess.annotation();
+	annotation.referencedDeclaration = possibleMembers.front().declaration;
+	annotation.type = possibleMembers.front().type;
+	if (exprType->category() == Type::Category::Struct)
+		annotation.isLValue = true;
+	else if (exprType->category() == Type::Category::Array)
+	{
+		auto const& arrayType(dynamic_cast<ArrayType const&>(*exprType));
+		annotation.isLValue = (
+			memberName == "length" &&
+			arrayType.location() == DataLocation::Storage &&
+			arrayType.isDynamicallySized()
+		);
+	}
+
+	return false;
+}
+
+bool TypeChecker::visit(IndexAccess const& _access)
+{
+	_access.baseExpression().accept(*this);
+	TypePointer baseType = type(_access.baseExpression());
+	TypePointer resultType;
+	bool isLValue = false;
+	Expression const* index = _access.indexExpression();
+	switch (baseType->category())
+	{
+	case Type::Category::Array:
+	{
+		ArrayType const& actualType = dynamic_cast<ArrayType const&>(*baseType);
+		if (!index)
+			typeError(_access, "Index expression cannot be omitted.");
+		else if (actualType.isString())
+		{
+			typeError(_access, "Index access for string is not possible.");
+			index->accept(*this);
+		}
+		else
+		{
+			expectType(*index, IntegerType(256));
+			if (auto integerType = dynamic_cast<IntegerConstantType const*>(type(*index).get()))
+				if (!actualType.isDynamicallySized() && actualType.length() <= integerType->literalValue(nullptr))
+					typeError(_access, "Out of bounds array access.");
+		}
+		resultType = actualType.baseType();
+		isLValue = actualType.location() != DataLocation::CallData;
+		break;
+	}
+	case Type::Category::Mapping:
+	{
+		MappingType const& actualType = dynamic_cast<MappingType const&>(*baseType);
+		if (!index)
+			typeError(_access, "Index expression cannot be omitted.");
+		else
+			expectType(*index, *actualType.keyType());
+		resultType = actualType.valueType();
+		isLValue = true;
+		break;
+	}
+	case Type::Category::TypeType:
+	{
+		TypeType const& typeType = dynamic_cast<TypeType const&>(*baseType);
+		if (!index)
+			resultType = make_shared<TypeType>(make_shared<ArrayType>(DataLocation::Memory, typeType.actualType()));
+		else
+		{
+			index->accept(*this);
+			if (auto length = dynamic_cast<IntegerConstantType const*>(type(*index).get()))
+				resultType = make_shared<TypeType>(make_shared<ArrayType>(
+					DataLocation::Memory,
+					typeType.actualType(),
+					length->literalValue(nullptr)
+				));
+			else
+				typeError(*index, "Integer constant expected.");
+		}
+		break;
+	}
+	default:
+		fatalTypeError(
+			_access.baseExpression(),
+			"Indexed expression has to be a type, mapping or array (is " + baseType->toString() + ")"
+		);
+	}
+	_access.annotation().type = move(resultType);
+	_access.annotation().isLValue = isLValue;
+
+	return false;
+}
+
+bool TypeChecker::visit(Identifier const& _identifier)
+{
+	ASTAnnotation& annotation = _identifier.annotation();
+	if (!annotation.referencedDeclaration)
+	{
+		if (!annotation.argumentTypes)
+			fatalTypeError(_identifier, "Unable to determine overloaded type.");
+		if (annotation.overloadedDeclarations.empty())
+			fatalTypeError(_identifier, "No candidates for overload resolution found.");
+		else if (annotation.overloadedDeclarations.size() == 1)
+			annotation.referencedDeclaration = *annotation.overloadedDeclarations.begin();
+		else
+		{
+			vector<Declaration const*> candidates;
+
+			for (Declaration const* declaration: annotation.overloadedDeclarations)
+			{
+				TypePointer function = declaration->type(_identifier.annotation().contractScope);
+				solAssert(!!function, "Requested type not present.");
+				auto const* functionType = dynamic_cast<FunctionType const*>(function.get());
+				if (functionType && functionType->canTakeArguments(*annotation.argumentTypes))
+					candidates.push_back(declaration);
+			}
+			if (candidates.empty())
+				fatalTypeError(_identifier, "No matching declaration found after argument-dependent lookup.");
+			else if (candidates.size() == 1)
+				annotation.referencedDeclaration = candidates.front();
+			else
+				fatalTypeError(_identifier, "No unique declaration found after argument-dependent lookup.");
+		}
+	}
+	solAssert(
+		!!annotation.referencedDeclaration,
+		"Referenced declaration is null after overload resolution."
+	);
+	annotation.isLValue = annotation.referencedDeclaration->isLValue();
+	annotation.type = annotation.referencedDeclaration->type(_identifier.annotation().contractScope);
+	if (!annotation.type)
+		fatalTypeError(_identifier, "Declaration referenced before type could be determined.");
+	return false;
+}
+
+void TypeChecker::endVisit(ElementaryTypeNameExpression const& _expr)
+{
+	_expr.annotation().type = make_shared<TypeType>(Type::fromElementaryTypeName(_expr.typeToken()));
+}
+
+void TypeChecker::endVisit(Literal const& _literal)
+{
+	_literal.annotation().type = Type::forLiteral(_literal);
+	if (!_literal.annotation().type)
+		fatalTypeError(_literal, "Invalid literal value.");
+}
+
+Declaration const& TypeChecker::dereference(Identifier const& _identifier)
+{
+	solAssert(!!_identifier.annotation().referencedDeclaration, "Declaration not stored.");
+	return *_identifier.annotation().referencedDeclaration;
+}
+
+void TypeChecker::expectType(Expression const& _expression, Type const& _expectedType)
+{
+	_expression.accept(*this);
+
+	if (!type(_expression)->isImplicitlyConvertibleTo(_expectedType))
+		typeError(
+			_expression,
+			"Type " +
+			type(_expression)->toString() +
+			" is not implicitly convertible to expected type " +
+			_expectedType.toString() +
+			"."
+		);
+}
+
+void TypeChecker::requireLValue(Expression const& _expression)
+{
+	_expression.accept(*this);
+	if (!_expression.annotation().isLValue)
+		typeError(_expression, "Expression has to be an lvalue.");
+	_expression.annotation().lValueRequested = true;
+}
+
+void TypeChecker::typeError(ASTNode const& _node, string const& _description)
+{
+	auto err = make_shared<TypeError>();
+	*err <<
+		errinfo_sourceLocation(_node.location()) <<
+		errinfo_comment(_description);
+
+	m_errors.push_back(move(err));
+}
+
+void TypeChecker::fatalTypeError(ASTNode const& _node, string const& _description)
+{
+	typeError(_node, _description);
+	BOOST_THROW_EXCEPTION(FatalError());
+}
diff --git a/libsolidity/TypeChecker.h b/libsolidity/TypeChecker.h
new file mode 100644
index 00000000..90e2a01b
--- /dev/null
+++ b/libsolidity/TypeChecker.h
@@ -0,0 +1,114 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Type analyzer and checker.
+ */
+
+#pragma once
+
+#include <libsolidity/TypeChecker.h>
+#include <libsolidity/Types.h>
+#include <libsolidity/ASTAnnotations.h>
+#include <libsolidity/ASTForward.h>
+#include <libsolidity/ASTVisitor.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+
+/**
+ * The module that performs type analysis on the AST, checks the applicability of operations on
+ * those types and stores errors for invalid operations.
+ * Provides a way to retrieve the type of an AST node.
+ */
+class TypeChecker: private ASTConstVisitor
+{
+public:
+	/// Performs type checking on the given contract and all of its sub-nodes.
+	/// @returns true iff all checks passed.
+	bool checkTypeRequirements(ContractDefinition const& _contract);
+
+	/// @returns the list of errors found during type checking.
+	std::vector<std::shared_ptr<Exception const>> const& errors() const { return m_errors; }
+
+	/// @returns the type of an expression and asserts that it is present.
+	TypePointer const& type(Expression const& _expression) const;
+	/// @returns the type of the given variable and throws if the type is not present
+	/// (this can happen for variables with non-explicit types before their types are resolved)
+	TypePointer const& type(VariableDeclaration const& _variable) const;
+
+	/// Adds a new error to the list of errors.
+	void typeError(ASTNode const& _node, std::string const& _description);
+	/// Adds a new error to the list of errors and throws to abort type checking.
+	void fatalTypeError(ASTNode const& _node, std::string const& _description);
+
+private:
+	virtual bool visit(ContractDefinition const& _contract) override;
+	/// Checks that two functions defined in this contract with the same name have different
+	/// arguments and that there is at most one constructor.
+	void checkContractDuplicateFunctions(ContractDefinition const& _contract);
+	void checkContractIllegalOverrides(ContractDefinition const& _contract);
+	void checkContractAbstractFunctions(ContractDefinition const& _contract);
+	void checkContractAbstractConstructors(ContractDefinition const& _contract);
+	/// Checks that different functions with external visibility end up having different
+	/// external argument types (i.e. different signature).
+	void checkContractExternalTypeClashes(ContractDefinition const& _contract);
+	/// Checks that all requirements for a library are fulfilled if this is a library.
+	void checkLibraryRequirements(ContractDefinition const& _contract);
+
+	virtual void endVisit(InheritanceSpecifier const& _inheritance) override;
+	virtual bool visit(StructDefinition const& _struct) override;
+	virtual bool visit(FunctionDefinition const& _function) override;
+	virtual bool visit(VariableDeclaration const& _variable) override;
+	/// We need to do this manually because we want to pass the bases of the current contract in
+	/// case this is a base constructor call.
+	void visitManually(ModifierInvocation const& _modifier, std::vector<ContractDefinition const*> const& _bases);
+	virtual bool visit(EventDefinition const& _eventDef) override;
+	virtual bool visit(IfStatement const& _ifStatement) override;
+	virtual bool visit(WhileStatement const& _whileStatement) override;
+	virtual bool visit(ForStatement const& _forStatement) override;
+	virtual void endVisit(Return const& _return) override;
+	virtual void endVisit(ExpressionStatement const& _statement) override;
+	virtual bool visit(Assignment const& _assignment) override;
+	virtual void endVisit(BinaryOperation const& _operation) override;
+	virtual bool visit(UnaryOperation const& _operation) override;
+	virtual bool visit(FunctionCall const& _functionCall) override;
+	virtual void endVisit(NewExpression const& _newExpression) override;
+	virtual bool visit(MemberAccess const& _memberAccess) override;
+	virtual bool visit(IndexAccess const& _indexAccess) override;
+	virtual bool visit(Identifier const& _identifier) override;
+	virtual void endVisit(ElementaryTypeNameExpression const& _expr) override;
+	virtual void endVisit(Literal const& _literal) override;
+
+	/// @returns the referenced declaration and throws on error.
+	Declaration const& dereference(Identifier const& _identifier);
+
+	/// Runs type checks on @a _expression to infer its type and then checks that it is implicitly
+	/// convertible to @a _expectedType.
+	void expectType(Expression const& _expression, Type const& _expectedType);
+	/// Runs type checks on @a _expression to infer its type and then checks that it is an LValue.
+	void requireLValue(Expression const& _expression);
+
+	std::vector<std::shared_ptr<Exception const>> m_errors;
+};
+
+}
+}
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index beb5becd..68e8e91d 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -157,55 +157,6 @@ TypePointer Type::fromElementaryTypeName(string const& _name)
 	return fromElementaryTypeName(Token::fromIdentifierOrKeyword(_name));
 }
 
-TypePointer Type::fromUserDefinedTypeName(UserDefinedTypeName const& _typeName)
-{
-	Declaration const* declaration = _typeName.referencedDeclaration();
-	if (StructDefinition const* structDef = dynamic_cast<StructDefinition const*>(declaration))
-		return make_shared<StructType>(*structDef);
-	else if (EnumDefinition const* enumDef = dynamic_cast<EnumDefinition const*>(declaration))
-		return make_shared<EnumType>(*enumDef);
-	else if (FunctionDefinition const* function = dynamic_cast<FunctionDefinition const*>(declaration))
-		return make_shared<FunctionType>(*function);
-	else if (ContractDefinition const* contract = dynamic_cast<ContractDefinition const*>(declaration))
-		return make_shared<ContractType>(*contract);
-	return TypePointer();
-}
-
-TypePointer Type::fromMapping(ElementaryTypeName& _keyType, TypeName& _valueType)
-{
-	TypePointer keyType = _keyType.toType();
-	if (!keyType)
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Error resolving type name."));
-	TypePointer valueType = _valueType.toType();
-	if (!valueType)
-		BOOST_THROW_EXCEPTION(_valueType.createTypeError("Invalid type name."));
-	// Convert value type to storage reference.
-	valueType = ReferenceType::copyForLocationIfReference(DataLocation::Storage, valueType);
-	// Convert key type to memory.
-	keyType = ReferenceType::copyForLocationIfReference(DataLocation::Memory, keyType);
-	return make_shared<MappingType>(keyType, valueType);
-}
-
-TypePointer Type::fromArrayTypeName(TypeName& _baseTypeName, Expression* _length)
-{
-	TypePointer baseType = _baseTypeName.toType();
-	if (!baseType)
-		BOOST_THROW_EXCEPTION(_baseTypeName.createTypeError("Invalid type name."));
-	if (baseType->storageBytes() == 0)
-		BOOST_THROW_EXCEPTION(_baseTypeName.createTypeError("Illegal base type of storage size zero for array."));
-	if (_length)
-	{
-		if (!_length->type())
-			_length->checkTypeRequirements(nullptr);
-		auto const* length = dynamic_cast<IntegerConstantType const*>(_length->type().get());
-		if (!length)
-			BOOST_THROW_EXCEPTION(_length->createTypeError("Invalid array length."));
-		return make_shared<ArrayType>(DataLocation::Storage, baseType, length->literalValue(nullptr));
-	}
-	else
-		return make_shared<ArrayType>(DataLocation::Storage, baseType);
-}
-
 TypePointer Type::forLiteral(Literal const& _literal)
 {
 	switch (_literal.token())
@@ -686,7 +637,7 @@ bool ContractType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 		return dynamic_cast<IntegerType const&>(_convertTo).isAddress();
 	if (_convertTo.category() == Category::Contract)
 	{
-		auto const& bases = contractDefinition().linearizedBaseContracts();
+		auto const& bases = contractDefinition().annotation().linearizedBaseContracts;
 		if (m_super && bases.size() <= 1)
 			return false;
 		return find(m_super ? ++bases.begin() : bases.begin(), bases.end(),
@@ -944,7 +895,7 @@ MemberList const& ContractType::members() const
 		if (m_super)
 		{
 			// add the most derived of all functions which are visible in derived contracts
-			for (ContractDefinition const* base: m_contract.linearizedBaseContracts())
+			for (ContractDefinition const* base: m_contract.annotation().linearizedBaseContracts)
 				for (ASTPointer<FunctionDefinition> const& function: base->definedFunctions())
 				{
 					if (!function->isVisibleInDerivedContracts())
@@ -998,13 +949,13 @@ shared_ptr<FunctionType const> const& ContractType::constructorType() const
 vector<tuple<VariableDeclaration const*, u256, unsigned>> ContractType::stateVariables() const
 {
 	vector<VariableDeclaration const*> variables;
-	for (ContractDefinition const* contract: boost::adaptors::reverse(m_contract.linearizedBaseContracts()))
+	for (ContractDefinition const* contract: boost::adaptors::reverse(m_contract.annotation().linearizedBaseContracts))
 		for (ASTPointer<VariableDeclaration> const& variable: contract->stateVariables())
 			if (!variable->isConstant())
 				variables.push_back(variable.get());
 	TypePointers types;
 	for (auto variable: variables)
-		types.push_back(variable->type());
+		types.push_back(variable->annotation().type);
 	StorageOffsets offsets;
 	offsets.computeOffsets(types);
 
@@ -1082,7 +1033,7 @@ MemberList const& StructType::members() const
 		MemberList::MemberMap members;
 		for (ASTPointer<VariableDeclaration> const& variable: m_struct.members())
 		{
-			TypePointer type = variable->type();
+			TypePointer type = variable->annotation().type;
 			// Skip all mapping members if we are not in storage.
 			if (location() != DataLocation::Storage && !type->canLiveOutsideStorage())
 				continue;
@@ -1147,7 +1098,7 @@ set<string> StructType::membersMissingInMemory() const
 {
 	set<string> missing;
 	for (ASTPointer<VariableDeclaration> const& variable: m_struct.members())
-		if (!variable->type()->canLiveOutsideStorage())
+		if (!variable->annotation().type->canLiveOutsideStorage())
 			missing.insert(variable->name());
 	return missing;
 }
@@ -1211,14 +1162,14 @@ FunctionType::FunctionType(FunctionDefinition const& _function, bool _isInternal
 	for (ASTPointer<VariableDeclaration> const& var: _function.parameters())
 	{
 		paramNames.push_back(var->name());
-		params.push_back(var->type());
+		params.push_back(var->annotation().type);
 	}
 	retParams.reserve(_function.returnParameters().size());
 	retParamNames.reserve(_function.returnParameters().size());
 	for (ASTPointer<VariableDeclaration> const& var: _function.returnParameters())
 	{
 		retParamNames.push_back(var->name());
-		retParams.push_back(var->type());
+		retParams.push_back(var->annotation().type);
 	}
 	swap(params, m_parameterTypes);
 	swap(paramNames, m_parameterNames);
@@ -1231,7 +1182,7 @@ FunctionType::FunctionType(VariableDeclaration const& _varDecl):
 {
 	TypePointers paramTypes;
 	vector<string> paramNames;
-	auto returnType = _varDecl.type();
+	auto returnType = _varDecl.annotation().type;
 
 	while (true)
 	{
@@ -1293,7 +1244,7 @@ FunctionType::FunctionType(const EventDefinition& _event):
 	for (ASTPointer<VariableDeclaration> const& var: _event.parameters())
 	{
 		paramNames.push_back(var->name());
-		params.push_back(var->type());
+		params.push_back(var->annotation().type);
 	}
 	swap(params, m_parameterTypes);
 	swap(paramNames, m_parameterNames);
@@ -1662,7 +1613,7 @@ MemberList const& TypeType::members() const
 					));
 			else if (m_currentContract != nullptr)
 			{
-				vector<ContractDefinition const*> currentBases = m_currentContract->linearizedBaseContracts();
+				auto const& currentBases = m_currentContract->annotation().linearizedBaseContracts;
 				if (find(currentBases.begin(), currentBases.end(), &contract) != currentBases.end())
 					// We are accessing the type of a base contract, so add all public and protected
 					// members. Note that this does not add inherited functions on purpose.
@@ -1687,7 +1638,7 @@ ModifierType::ModifierType(const ModifierDefinition& _modifier)
 	TypePointers params;
 	params.reserve(_modifier.parameters().size());
 	for (ASTPointer<VariableDeclaration> const& var: _modifier.parameters())
-		params.push_back(var->type());
+		params.push_back(var->annotation().type);
 	swap(params, m_parameterTypes);
 }