path: root/AST.cpp

/*
    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
 * Solidity abstract syntax tree.
 */

#include <algorithm>
#include <boost/range/adaptor/reversed.hpp>
#include <libsolidity/Utils.h>
#include <libsolidity/AST.h>
#include <libsolidity/ASTVisitor.h>
#include <libsolidity/Exceptions.h>
#include <libsolidity/AST_accept.h>

#include <libdevcrypto/SHA3.h>

using namespace std;

namespace dev
{
namespace solidity
{

TypeError ASTNode::createTypeError(string const& _description) const
{
    return TypeError() << errinfo_sourceLocation(getLocation()) << errinfo_comment(_description);
}

TypePointer ContractDefinition::getType(ContractDefinition const* _currentContract) const
{
    return make_shared<TypeType>(make_shared<ContractType>(*this), _currentContract);
}

void ContractDefinition::checkTypeRequirements()
{
    for (ASTPointer<InheritanceSpecifier> const& baseSpecifier: getBaseContracts())
        baseSpecifier->checkTypeRequirements();

    checkDuplicateFunctions();
    checkIllegalOverrides();
    checkAbstractFunctions();
    checkAbstractConstructors();

    FunctionDefinition const* constructor = getConstructor();
    if (constructor && !constructor->getReturnParameters().empty())
        BOOST_THROW_EXCEPTION(constructor->getReturnParameterList()->createTypeError(
                                    "Non-empty \"returns\" directive for constructor."));

    FunctionDefinition const* fallbackFunction = nullptr;
    for (ASTPointer<FunctionDefinition> const& function: getDefinedFunctions())
    {
        if (function->getName().empty())
        {
            if (fallbackFunction)
                BOOST_THROW_EXCEPTION(DeclarationError() << errinfo_comment("Only one fallback function is allowed."));
            else
            {
                fallbackFunction = function.get();
                if (!fallbackFunction->getParameters().empty())
                    BOOST_THROW_EXCEPTION(fallbackFunction->getParameterList().createTypeError("Fallback function cannot take parameters."));
            }
        }
        if (!function->isFullyImplemented())
            setFullyImplemented(false);
    }
    for (ASTPointer<ModifierDefinition> const& modifier: getFunctionModifiers())
        modifier->checkTypeRequirements();

    for (ASTPointer<FunctionDefinition> const& function: getDefinedFunctions())
        function->checkTypeRequirements();

    for (ASTPointer<VariableDeclaration> const& variable: m_stateVariables)
        variable->checkTypeRequirements();

    checkExternalTypeClashes();
    // check for hash collisions in function signatures
    set<FixedHash<4>> hashes;
    for (auto const& it: getInterfaceFunctionList())
    {
        FixedHash<4> const& hash = it.first;
        if (hashes.count(hash))
            BOOST_THROW_EXCEPTION(createTypeError(
                                      std::string("Function signature hash collision for ") +
                                      it.second->externalSignature()));
        hashes.insert(hash);
    }
}

map<FixedHash<4>, FunctionTypePointer> ContractDefinition::getInterfaceFunctions() const
{
    auto exportedFunctionList = getInterfaceFunctionList();

    map<FixedHash<4>, FunctionTypePointer> exportedFunctions;
    for (auto const& it: exportedFunctionList)
        exportedFunctions.insert(it);

    solAssert(exportedFunctionList.size() == exportedFunctions.size(),
              "Hash collision at Function Definition Hash calculation");

    return exportedFunctions;
}

FunctionDefinition const* ContractDefinition::getConstructor() const
{
    for (ASTPointer<FunctionDefinition> const& f: m_definedFunctions)
        if (f->isConstructor())
            return f.get();
    return nullptr;
}

FunctionDefinition const* ContractDefinition::getFallbackFunction() const
{
    for (ContractDefinition const* contract: getLinearizedBaseContracts())
        for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
            if (f->getName().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: getDefinedFunctions())
        functions[function->getName()].push_back(function.get());

    if (functions[getName()].size() > 1)
    {
        SecondarySourceLocation ssl;
        auto it = functions[getName()].begin();
        ++it;
        for(; it != functions[getName()].end(); ++it)
            ssl.append("Another declaration is here:", (*it)->getLocation());

        BOOST_THROW_EXCEPTION(
            DeclarationError() <<
            errinfo_sourceLocation(getConstructor()->getLocation()) <<
            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]->getLocation()) <<
                        errinfo_comment("Function with same name and arguments already defined.") <<
                        errinfo_secondarySourceLocation(SecondarySourceLocation().append(
                            "The previous declaration is here:", overloads[i]->getLocation()))
                    );
    }
}

void ContractDefinition::checkAbstractFunctions()
{
    map<string, bool> functions;

    // Search from base to derived
    for (ContractDefinition const* contract: boost::adaptors::reverse(getLinearizedBaseContracts()))
        for (ASTPointer<FunctionDefinition> const& function: contract->getDefinedFunctions())
        {
            string const& name = function->getName();
            if (!function->isFullyImplemented() && functions.count(name) && functions[name])
                BOOST_THROW_EXCEPTION(function->createTypeError("Redeclaring an already implemented function as abstract"));
            functions[name] = function->isFullyImplemented();
        }

    for (auto const& it: functions)
        if (!it.second)
        {
            setFullyImplemented(false);
            break;
        }
}

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 = getLinearizedBaseContracts();
    for (ContractDefinition const* contract: bases)
        if (FunctionDefinition const* constructor = contract->getConstructor())
            if (contract != this && !constructor->getParameters().empty())
                argumentsNeeded.insert(contract);

    for (ContractDefinition const* contract: bases)
    {
        if (FunctionDefinition const* constructor = contract->getConstructor())
            for (auto const& modifier: constructor->getModifiers())
            {
                auto baseContract = dynamic_cast<ContractDefinition const*>(
                    &modifier->getName()->getReferencedDeclaration()
                );
                if (baseContract)
                    argumentsNeeded.erase(baseContract);
            }


        for (ASTPointer<InheritanceSpecifier> const& base: contract->getBaseContracts())
        {
            auto baseContract = dynamic_cast<ContractDefinition const*>(
                &base->getName()->getReferencedDeclaration()
            );
            solAssert(baseContract, "");
            if (!base->getArguments().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: getLinearizedBaseContracts())
    {
        for (ASTPointer<FunctionDefinition> const& function: contract->getDefinedFunctions())
        {
            if (function->isConstructor())
                continue; // constructors can neither be overridden nor override anything
            string const& name = function->getName();
            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->getVisibility() != function->getVisibility() ||
                    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->getFunctionModifiers())
        {
            string const& name = modifier->getName();
            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: getLinearizedBaseContracts())
    {
        for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
            if (f->isPartOfExternalInterface())
            {
                auto functionType = make_shared<FunctionType>(*f);
                externalDeclarations[functionType->externalSignature(f->getName())].push_back(
                    make_pair(f.get(), functionType)
                );
            }
        for (ASTPointer<VariableDeclaration> const& v: contract->getStateVariables())
            if (v->isPartOfExternalInterface())
            {
                auto functionType = make_shared<FunctionType>(*v);
                externalDeclarations[functionType->externalSignature(v->getName())].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."
                    ));
}

std::vector<ASTPointer<EventDefinition>> const& ContractDefinition::getInterfaceEvents() const
{
    if (!m_interfaceEvents)
    {
        set<string> eventsSeen;
        m_interfaceEvents.reset(new std::vector<ASTPointer<EventDefinition>>());
        for (ContractDefinition const* contract: getLinearizedBaseContracts())
            for (ASTPointer<EventDefinition> const& e: contract->getEvents())
                if (eventsSeen.count(e->getName()) == 0)
                {
                    eventsSeen.insert(e->getName());
                    m_interfaceEvents->push_back(e);
                }
    }
    return *m_interfaceEvents;
}

vector<pair<FixedHash<4>, FunctionTypePointer>> const& ContractDefinition::getInterfaceFunctionList() const
{
    if (!m_interfaceFunctionList)
    {
        set<string> functionsSeen;
        set<string> signaturesSeen;
        m_interfaceFunctionList.reset(new vector<pair<FixedHash<4>, FunctionTypePointer>>());
        for (ContractDefinition const* contract: getLinearizedBaseContracts())
        {
            for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
            {
                string functionSignature = f->externalSignature();
                if (f->isPartOfExternalInterface() && signaturesSeen.count(functionSignature) == 0)
                {
                    functionsSeen.insert(f->getName());
                    signaturesSeen.insert(functionSignature);
                    FixedHash<4> hash(dev::sha3(functionSignature));
                    m_interfaceFunctionList->push_back(make_pair(hash, make_shared<FunctionType>(*f, false)));
                }
            }

            for (ASTPointer<VariableDeclaration> const& v: contract->getStateVariables())
                if (functionsSeen.count(v->getName()) == 0 && v->isPartOfExternalInterface())
                {
                    FunctionType ftype(*v);
                    solAssert(v->getType().get(), "");
                    functionsSeen.insert(v->getName());
                    FixedHash<4> hash(dev::sha3(ftype.externalSignature(v->getName())));
                    m_interfaceFunctionList->push_back(make_pair(hash, make_shared<FunctionType>(*v)));
                }
        }
    }
    return *m_interfaceFunctionList;
}

vector<Declaration const*> const& ContractDefinition::getInheritableMembers() const
{
    if (!m_inheritableMembers)
    {
        set<string> memberSeen;
        m_inheritableMembers.reset(new vector<Declaration const*>());
        auto addInheritableMember = [&](Declaration const* _decl)
        {
            if (memberSeen.count(_decl->getName()) == 0 && _decl->isVisibleInDerivedContracts())
            {
                memberSeen.insert(_decl->getName());
                m_inheritableMembers->push_back(_decl);
            }
        };

        for (ASTPointer<FunctionDefinition> const& f: getDefinedFunctions())
            addInheritableMember(f.get());

        for (ASTPointer<VariableDeclaration> const& v: getStateVariables())
            addInheritableMember(v.get());

        for (ASTPointer<StructDefinition> const& s: getDefinedStructs())
            addInheritableMember(s.get());
    }
    return *m_inheritableMembers;
}

TypePointer EnumValue::getType(ContractDefinition const*) const
{
    EnumDefinition const* parentDef = dynamic_cast<EnumDefinition const*>(getScope());
    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->getReferencedDeclaration());
    solAssert(base, "Base contract not available.");
    TypePointers parameterTypes = ContractType(*base).getConstructorType()->getParameterTypes();
    if (!m_arguments.empty() && parameterTypes.size() != m_arguments.size())
        BOOST_THROW_EXCEPTION(createTypeError("Wrong argument count for constructor call."));
    for (size_t i = 0; i < m_arguments.size(); ++i)
        if (!m_arguments[i]->getType()->isImplicitlyConvertibleTo(*parameterTypes[i]))
            BOOST_THROW_EXCEPTION(createTypeError("Invalid type for argument in constructer call."));
}

TypePointer StructDefinition::getType(ContractDefinition const*) const
{
    return make_shared<TypeType>(make_shared<StructType>(*this));
}

void StructDefinition::checkMemberTypes() const
{
    for (ASTPointer<VariableDeclaration> const& member: getMembers())
        if (!member->getType()->canBeStored())
            BOOST_THROW_EXCEPTION(member->createTypeError("Type cannot be used in struct."));
}

void StructDefinition::checkRecursion() const
{
    set<StructDefinition const*> definitionsSeen;
    vector<StructDefinition const*> queue = {this};
    while (!queue.empty())
    {
        StructDefinition const* def = queue.back();
        queue.pop_back();
        if (definitionsSeen.count(def))
            BOOST_THROW_EXCEPTION(ParserError() << errinfo_sourceLocation(def->getLocation())
                                                << errinfo_comment("Recursive struct definition."));
        definitionsSeen.insert(def);
        for (ASTPointer<VariableDeclaration> const& member: def->getMembers())
            if (member->getType()->getCategory() == Type::Category::Struct)
            {
                UserDefinedTypeName const& typeName = dynamic_cast<UserDefinedTypeName const&>(*member->getTypeName());
                queue.push_back(&dynamic_cast<StructDefinition const&>(*typeName.getReferencedDeclaration()));
            }
    }
}

TypePointer EnumDefinition::getType(ContractDefinition const*) const
{
    return make_shared<TypeType>(make_shared<EnumType>(*this));
}

TypePointer FunctionDefinition::getType(ContractDefinition const*) const
{
    return make_shared<FunctionType>(*this);
}

void FunctionDefinition::checkTypeRequirements()
{
    for (ASTPointer<VariableDeclaration> const& var: getParameters() + getReturnParameters())
    {
        if (!var->getType()->canLiveOutsideStorage())
            BOOST_THROW_EXCEPTION(var->createTypeError("Type is required to live outside storage."));
        // todo delete when will be implemented arrays as parameter type in internal functions
        if (getVisibility() == Visibility::Public && var->getType()->getCategory() == Type::Category::Array)
            BOOST_THROW_EXCEPTION(var->createTypeError("Arrays only implemented for external functions."));
        if (getVisibility() >= Visibility::Public && !(var->getType()->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&>(*getScope()).getLinearizedBaseContracts() :
            vector<ContractDefinition const*>());
    if (m_body)
        m_body->checkTypeRequirements();
}

string FunctionDefinition::externalSignature() const
{
    return FunctionType(*this).externalSignature(getName());
}

bool VariableDeclaration::isLValue() const
{
    // External function parameters and constant declared variables are Read-Only
    return !isExternalFunctionParameter() && !m_isConstant;
}

void VariableDeclaration::checkTypeRequirements()
{
    // 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*>(getScope()))
            BOOST_THROW_EXCEPTION(createTypeError("Illegal use of \"constant\" specifier."));
        if ((m_type && !m_type->isValueType()) || !m_value)
            BOOST_THROW_EXCEPTION(createTypeError("Unitialized \"constant\" variable."));
    }
    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);

        TypePointer type = m_value->getType();
        if (type->getCategory() == Type::Category::IntegerConstant)
        {
            auto intType = dynamic_pointer_cast<IntegerConstantType const>(type)->getIntegerType();
            if (!intType)
                BOOST_THROW_EXCEPTION(m_value->createTypeError("Invalid integer constant " + type->toString() + "."));
            type = intType;
        }
        else if (type->getCategory() == Type::Category::Void)
            BOOST_THROW_EXCEPTION(createTypeError("Variable cannot have void type."));
        m_type = type;
    }
    if (m_isStateVariable && getVisibility() >= Visibility::Public && !FunctionType(*this).externalType())
        BOOST_THROW_EXCEPTION(createTypeError("Internal type is not allowed for public state variables."));
}

bool VariableDeclaration::isExternalFunctionParameter() const
{
    auto const* function = dynamic_cast<FunctionDefinition const*>(getScope());
    if (!function || function->getVisibility() != Declaration::Visibility::External)
        return false;
    for (auto const& variable: function->getParameters())
        if (variable.get() == this)
            return true;
    return false;
}

TypePointer ModifierDefinition::getType(ContractDefinition const*) 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->getType());
    }
    m_modifierName->checkTypeRequirements(&argumentTypes);

    auto const* declaration = &m_modifierName->getReferencedDeclaration();
    vector<ASTPointer<VariableDeclaration>> emptyParameterList;
    vector<ASTPointer<VariableDeclaration>> const* parameters = nullptr;
    if (auto modifier = dynamic_cast<ModifierDefinition const*>(declaration))
        parameters = &modifier->getParameters();
    else
        // check parameters for Base constructors
        for (ContractDefinition const* base: _bases)
            if (declaration == base)
            {
                if (auto referencedConstructor = base->getConstructor())
                    parameters = &referencedConstructor->getParameters();
                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."));
    for (size_t i = 0; i < m_arguments.size(); ++i)
        if (!m_arguments[i]->getType()->isImplicitlyConvertibleTo(*(*parameters)[i]->getType()))
            BOOST_THROW_EXCEPTION(createTypeError("Invalid type for argument in modifier invocation."));
}

void EventDefinition::checkTypeRequirements()
{
    int numIndexed = 0;
    for (ASTPointer<VariableDeclaration> const& var: getParameters())
    {
        if (var->isIndexed())
            numIndexed++;
        if (!var->getType()->canLiveOutsideStorage())
            BOOST_THROW_EXCEPTION(var->createTypeError("Type is required to live outside storage."));
        if (!var->getType()->externalType())
            BOOST_THROW_EXCEPTION(var->createTypeError("Internal type is not allowed as event parameter type."));
    }
    if (numIndexed > 3)
        BOOST_THROW_EXCEPTION(createTypeError("More than 3 indexed arguments for event."));
}

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->getParameters().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->getParameters().front()->getType());
}

void VariableDeclarationStatement::checkTypeRequirements()
{
    m_variable->checkTypeRequirements();
}

void Assignment::checkTypeRequirements(TypePointers const*)
{
    m_leftHandSide->checkTypeRequirements(nullptr);
    m_leftHandSide->requireLValue();
    if (m_leftHandSide->getType()->getCategory() == Type::Category::Mapping)
        BOOST_THROW_EXCEPTION(createTypeError("Mappings cannot be assigned to."));
    m_type = m_leftHandSide->getType();
    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->getType());
        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->getType()->toString()));
    }
}

void ExpressionStatement::checkTypeRequirements()
{
    m_expression->checkTypeRequirements(nullptr);
    if (m_expression->getType()->getCategory() == Type::Category::IntegerConstant)
        if (!dynamic_pointer_cast<IntegerConstantType const>(m_expression->getType())->getIntegerType())
            BOOST_THROW_EXCEPTION(m_expression->createTypeError("Invalid integer constant."));
}

void Expression::expectType(Type const& _expectedType)
{
    checkTypeRequirements(nullptr);
    Type const& type = *getType();
    if (!type.isImplicitlyConvertibleTo(_expectedType))
        BOOST_THROW_EXCEPTION(createTypeError("Type " + type.toString() +
                                              " 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->getType()->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->getType()->binaryOperatorResult(m_operator, m_right->getType());
    if (!m_commonType)
        BOOST_THROW_EXCEPTION(createTypeError("Operator " + string(Token::toString(m_operator)) +
                                              " not compatible with types " +
                                              m_left->getType()->toString() + " and " +
                                              m_right->getType()->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->getType());
    }

    m_expression->checkTypeRequirements(isPositionalCall ? &argumentTypes : nullptr);

    Type const* expressionType = m_expression->getType().get();
    if (isTypeConversion())
    {
        TypeType const& type = dynamic_cast<TypeType const&>(*expressionType);
        //@todo for structs, we have to check the number of arguments to be equal to the
        // number of non-mapping members
        if (m_arguments.size() != 1)
            BOOST_THROW_EXCEPTION(createTypeError("More than one argument for explicit type conversion."));
        if (!isPositionalCall)
            BOOST_THROW_EXCEPTION(createTypeError("Type conversion cannot allow named arguments."));
        if (!m_arguments.front()->getType()->isExplicitlyConvertibleTo(*type.getActualType()))
            BOOST_THROW_EXCEPTION(createTypeError("Explicit type conversion not allowed."));
        m_type = type.getActualType();
    }
    else if (FunctionType const* functionType = dynamic_cast<FunctionType const*>(expressionType))
    {
        //@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->getParameterTypes();
        if (!functionType->takesArbitraryParameters() && parameterTypes.size() != m_arguments.size())
            BOOST_THROW_EXCEPTION(createTypeError("Wrong argument count for function call."));

        if (isPositionalCall)
        {
            // call by positional arguments
            for (size_t i = 0; i < m_arguments.size(); ++i)
                if (!functionType->takesArbitraryParameters() &&
                        !m_arguments[i]->getType()->isImplicitlyConvertibleTo(*parameterTypes[i]))
                    BOOST_THROW_EXCEPTION(m_arguments[i]->createTypeError("Invalid type for argument in function call."));
        }
        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->getParameterNames();
            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]->getType()->isImplicitlyConvertibleTo(*parameterTypes[j]))
                            BOOST_THROW_EXCEPTION(createTypeError("Invalid type for argument in function call."));

                        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 structs
        if (functionType->getReturnParameterTypes().empty())
            m_type = make_shared<VoidType>();
        else
            m_type = functionType->getReturnParameterTypes().front();
    }
    else
        BOOST_THROW_EXCEPTION(createTypeError("Type is not callable."));
}

bool FunctionCall::isTypeConversion() const
{
    return m_expression->getType()->getCategory() == Type::Category::TypeType;
}

void NewExpression::checkTypeRequirements(TypePointers const*)
{
    m_contractName->checkTypeRequirements(nullptr);
    m_contract = dynamic_cast<ContractDefinition const*>(&m_contractName->getReferencedDeclaration());
    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."));
    shared_ptr<ContractType const> contractType = make_shared<ContractType>(*m_contract);
    TypePointers const& parameterTypes = contractType->getConstructorType()->getParameterTypes();
    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->getType();

    MemberList::MemberMap possibleMembers = type.getMembers().membersByName(*m_memberName);
    if (possibleMembers.size() > 1 && _argumentTypes)
    {
        // do override resolution
        for (auto it = possibleMembers.begin(); it != possibleMembers.end();)
            if (
                it->type->getCategory() == Type::Category::Function &&
                !dynamic_cast<FunctionType const&>(*it->type).canTakeArguments(*_argumentTypes)
            )
                it = possibleMembers.erase(it);
            else
                ++it;
    }
    if (possibleMembers.size() == 0)
        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.getCategory() == Type::Category::Struct)
        m_isLValue = true;
    else if (type.getCategory() == Type::Category::Array)
    {
        auto const& arrayType(dynamic_cast<ArrayType const&>(type));
        m_isLValue = (*m_memberName == "length" &&
            arrayType.getLocation() != ArrayType::Location::CallData && arrayType.isDynamicallySized());
    }
    else
        m_isLValue = false;
}

void IndexAccess::checkTypeRequirements(TypePointers const*)
{
    m_base->checkTypeRequirements(nullptr);
    switch (m_base->getType()->getCategory())
    {
    case Type::Category::Array:
    {
        ArrayType const& type = dynamic_cast<ArrayType const&>(*m_base->getType());
        if (!m_index)
            BOOST_THROW_EXCEPTION(createTypeError("Index expression cannot be omitted."));
        m_index->expectType(IntegerType(256));
        if (type.isByteArray())
            m_type = make_shared<FixedBytesType>(1);
        else
            m_type = type.getBaseType();
        m_isLValue = type.getLocation() != ArrayType::Location::CallData;
        break;
    }
    case Type::Category::Mapping:
    {
        MappingType const& type = dynamic_cast<MappingType const&>(*m_base->getType());
        if (!m_index)
            BOOST_THROW_EXCEPTION(createTypeError("Index expression cannot be omitted."));
        m_index->expectType(*type.getKeyType());
        m_type = type.getValueType();
        m_isLValue = true;
        break;
    }
    case Type::Category::TypeType:
    {
        TypeType const& type = dynamic_cast<TypeType const&>(*m_base->getType());
        if (!m_index)
            m_type = make_shared<TypeType>(make_shared<ArrayType>(ArrayType::Location::Memory, type.getActualType()));
        else
        {
            m_index->checkTypeRequirements(nullptr);
            auto length = dynamic_cast<IntegerConstantType const*>(m_index->getType().get());
            if (!length)
                BOOST_THROW_EXCEPTION(m_index->createTypeError("Integer constant expected."));
            m_type = make_shared<TypeType>(make_shared<ArrayType>(
                ArrayType::Location::Memory, type.getActualType(), length->literalValue(nullptr)));
        }
        break;
    }
    default:
        BOOST_THROW_EXCEPTION(m_base->createTypeError(
            "Indexed expression has to be a type, mapping or array (is " + m_base->getType()->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->getType(m_currentContract);
    if (!m_type)
        BOOST_THROW_EXCEPTION(createTypeError("Declaration referenced before type could be determined."));
}

Declaration const& Identifier::getReferencedDeclaration() 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.");

    std::vector<Declaration const*> possibles;
    if (m_overloadedDeclarations.size() == 1)
        m_referencedDeclaration = *m_overloadedDeclarations.begin();

    for (Declaration const* declaration: m_overloadedDeclarations)
    {
        TypePointer const& function = declaration->getType();
        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));
}

void Literal::checkTypeRequirements(TypePointers const*)
{
    m_type = Type::forLiteral(*this);
    if (!m_type)
        BOOST_THROW_EXCEPTION(createTypeError("Invalid literal value."));
}

}
}