path: root/Parser.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 parser.
 */

#include <vector>
#include <libdevcore/Log.h>
#include <libsolidity/BaseTypes.h>
#include <libsolidity/Parser.h>
#include <libsolidity/Scanner.h>
#include <libsolidity/Exceptions.h>

using namespace std;

namespace dev
{
namespace solidity
{

/// AST node factory that also tracks the begin and end position of an AST node
/// while it is being parsed
class Parser::ASTNodeFactory
{
public:
    ASTNodeFactory(Parser const& _parser):
        m_parser(_parser), m_location(_parser.getPosition(), -1, _parser.getSourceName()) {}

    void markEndPosition() { m_location.end = m_parser.getEndPosition(); }
    void setLocationEmpty() { m_location.end = m_location.start; }
    /// Set the end position to the one of the given node.
    void setEndPositionFromNode(ASTPointer<ASTNode> const& _node) { m_location.end = _node->getLocation().end; }

    template <class NodeType, typename... Args>
    ASTPointer<NodeType> createNode(Args&& ... _args)
    {
        if (m_location.end < 0)
            markEndPosition();
        return make_shared<NodeType>(m_location, forward<Args>(_args)...);
    }

private:
    Parser const& m_parser;
    Location m_location;
};

ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
{
    m_scanner = _scanner;
    ASTNodeFactory nodeFactory(*this);
    vector<ASTPointer<ASTNode>> nodes;
    while (_scanner->getCurrentToken() != Token::EOS)
    {
        switch (m_scanner->getCurrentToken())
        {
        case Token::IMPORT:
            nodes.push_back(parseImportDirective());
            break;
        case Token::CONTRACT:
            nodes.push_back(parseContractDefinition());
            break;
        default:
            BOOST_THROW_EXCEPTION(createParserError(std::string("Expected import directive or contract definition.")));
        }
    }
    return nodeFactory.createNode<SourceUnit>(nodes);
}

std::shared_ptr<const string> const& Parser::getSourceName() const
{
    return m_scanner->getSourceName();
}

int Parser::getPosition() const
{
    return m_scanner->getCurrentLocation().start;
}

int Parser::getEndPosition() const
{
    return m_scanner->getCurrentLocation().end;
}

ASTPointer<ImportDirective> Parser::parseImportDirective()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::IMPORT);
    if (m_scanner->getCurrentToken() != Token::STRING_LITERAL)
        BOOST_THROW_EXCEPTION(createParserError("Expected string literal (URL)."));
    ASTPointer<ASTString> url = getLiteralAndAdvance();
    nodeFactory.markEndPosition();
    expectToken(Token::SEMICOLON);
    return nodeFactory.createNode<ImportDirective>(url);
}

ASTPointer<ContractDefinition> Parser::parseContractDefinition()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<ASTString> docString;
    if (m_scanner->getCurrentCommentLiteral() != "")
        docString = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());
    expectToken(Token::CONTRACT);
    ASTPointer<ASTString> name = expectIdentifierToken();
    vector<ASTPointer<InheritanceSpecifier>> baseContracts;
    vector<ASTPointer<StructDefinition>> structs;
    vector<ASTPointer<VariableDeclaration>> stateVariables;
    vector<ASTPointer<FunctionDefinition>> functions;
    vector<ASTPointer<ModifierDefinition>> modifiers;
    vector<ASTPointer<EventDefinition>> events;
    if (m_scanner->getCurrentToken() == Token::IS)
        do
        {
            m_scanner->next();
            baseContracts.push_back(parseInheritanceSpecifier());
        }
        while (m_scanner->getCurrentToken() == Token::COMMA);
    expectToken(Token::LBRACE);
    bool visibilityIsPublic = true;
    while (true)
    {
        Token::Value currentToken = m_scanner->getCurrentToken();
        if (currentToken == Token::RBRACE)
            break;
        else if (currentToken == Token::PUBLIC || currentToken == Token::PRIVATE)
        {
            visibilityIsPublic = (m_scanner->getCurrentToken() == Token::PUBLIC);
            m_scanner->next();
            expectToken(Token::COLON);
        }
        else if (currentToken == Token::FUNCTION)
            functions.push_back(parseFunctionDefinition(visibilityIsPublic, name.get()));
        else if (currentToken == Token::STRUCT)
            structs.push_back(parseStructDefinition());
        else if (currentToken == Token::IDENTIFIER || currentToken == Token::MAPPING ||
                 Token::isElementaryTypeName(currentToken))
        {
            VarDeclParserOptions options;
            options.isPublic = visibilityIsPublic;
            options.isStateVariable = true;
            stateVariables.push_back(parseVariableDeclaration(options));
            expectToken(Token::SEMICOLON);
        }
        else if (currentToken == Token::MODIFIER)
            modifiers.push_back(parseModifierDefinition());
        else if (currentToken == Token::EVENT)
            events.push_back(parseEventDefinition());
        else
            BOOST_THROW_EXCEPTION(createParserError("Function, variable, struct or modifier declaration expected."));
    }
    nodeFactory.markEndPosition();
    expectToken(Token::RBRACE);
    return nodeFactory.createNode<ContractDefinition>(name, docString, baseContracts, structs,
                                                      stateVariables, functions, modifiers, events);
}

ASTPointer<InheritanceSpecifier> Parser::parseInheritanceSpecifier()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Identifier> name(parseIdentifier());
    vector<ASTPointer<Expression>> arguments;
    if (m_scanner->getCurrentToken() == Token::LPAREN)
    {
        m_scanner->next();
        arguments = parseFunctionCallArguments();
        nodeFactory.markEndPosition();
        expectToken(Token::RPAREN);
    }
    else
        nodeFactory.setEndPositionFromNode(name);
    return nodeFactory.createNode<InheritanceSpecifier>(name, arguments);
}

ASTPointer<FunctionDefinition> Parser::parseFunctionDefinition(bool _isPublic, ASTString const* _contractName)
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<ASTString> docstring;
    if (m_scanner->getCurrentCommentLiteral() != "")
        docstring = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());

    expectToken(Token::FUNCTION);
    ASTPointer<ASTString> name;
    if (m_scanner->getCurrentToken() == Token::LPAREN)
        name = make_shared<ASTString>(); // anonymous function
    else
        name = expectIdentifierToken();
    ASTPointer<ParameterList> parameters(parseParameterList());
    bool isDeclaredConst = false;
    vector<ASTPointer<ModifierInvocation>> modifiers;
    while (true)
    {
        if (m_scanner->getCurrentToken() == Token::CONST)
        {
            isDeclaredConst = true;
            m_scanner->next();
        }
        else if (m_scanner->getCurrentToken() == Token::IDENTIFIER)
            modifiers.push_back(parseModifierInvocation());
        else
            break;
    }
    ASTPointer<ParameterList> returnParameters;
    if (m_scanner->getCurrentToken() == Token::RETURNS)
    {
        bool const permitEmptyParameterList = false;
        m_scanner->next();
        returnParameters = parseParameterList(permitEmptyParameterList);
    }
    else
        returnParameters = createEmptyParameterList();
    ASTPointer<Block> block = parseBlock();
    nodeFactory.setEndPositionFromNode(block);
    bool const c_isConstructor = (_contractName && *name == *_contractName);
    return nodeFactory.createNode<FunctionDefinition>(name, _isPublic, c_isConstructor, docstring,
                                                      parameters, isDeclaredConst, modifiers,
                                                      returnParameters, block);
}

ASTPointer<StructDefinition> Parser::parseStructDefinition()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::STRUCT);
    ASTPointer<ASTString> name = expectIdentifierToken();
    vector<ASTPointer<VariableDeclaration>> members;
    expectToken(Token::LBRACE);
    while (m_scanner->getCurrentToken() != Token::RBRACE)
    {
        members.push_back(parseVariableDeclaration());
        expectToken(Token::SEMICOLON);
    }
    nodeFactory.markEndPosition();
    expectToken(Token::RBRACE);
    return nodeFactory.createNode<StructDefinition>(name, members);
}

ASTPointer<VariableDeclaration> Parser::parseVariableDeclaration(VarDeclParserOptions const& _options)
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<TypeName> type = parseTypeName(_options.allowVar);
    bool isIndexed = false;
    if (_options.allowIndexed && m_scanner->getCurrentToken() == Token::INDEXED)
    {
        isIndexed = true;
        m_scanner->next();
    }
    nodeFactory.markEndPosition();
    return nodeFactory.createNode<VariableDeclaration>(type, expectIdentifierToken(),
                                                       _options.isPublic, _options.isStateVariable,
                                                       isIndexed);
}

ASTPointer<ModifierDefinition> Parser::parseModifierDefinition()
{
    ScopeGuard resetModifierFlag([this]() { m_insideModifier = false; });
    m_insideModifier = true;

    ASTNodeFactory nodeFactory(*this);
    ASTPointer<ASTString> docstring;
    if (m_scanner->getCurrentCommentLiteral() != "")
        docstring = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());

    expectToken(Token::MODIFIER);
    ASTPointer<ASTString> name(expectIdentifierToken());
    ASTPointer<ParameterList> parameters;
    if (m_scanner->getCurrentToken() == Token::LPAREN)
        parameters = parseParameterList();
    else
        parameters = createEmptyParameterList();
    ASTPointer<Block> block = parseBlock();
    nodeFactory.setEndPositionFromNode(block);
    return nodeFactory.createNode<ModifierDefinition>(name, docstring, parameters, block);
}

ASTPointer<EventDefinition> Parser::parseEventDefinition()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<ASTString> docstring;
    if (m_scanner->getCurrentCommentLiteral() != "")
        docstring = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());

    expectToken(Token::EVENT);
    ASTPointer<ASTString> name(expectIdentifierToken());
    ASTPointer<ParameterList> parameters;
    if (m_scanner->getCurrentToken() == Token::LPAREN)
        parameters = parseParameterList(true, true);
    else
        parameters = createEmptyParameterList();
    nodeFactory.markEndPosition();
    expectToken(Token::SEMICOLON);
    return nodeFactory.createNode<EventDefinition>(name, docstring, parameters);
}

ASTPointer<ModifierInvocation> Parser::parseModifierInvocation()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Identifier> name(parseIdentifier());
    vector<ASTPointer<Expression>> arguments;
    if (m_scanner->getCurrentToken() == Token::LPAREN)
    {
        m_scanner->next();
        arguments = parseFunctionCallArguments();
        nodeFactory.markEndPosition();
        expectToken(Token::RPAREN);
    }
    else
        nodeFactory.setEndPositionFromNode(name);
    return nodeFactory.createNode<ModifierInvocation>(name, arguments);
}

ASTPointer<Identifier> Parser::parseIdentifier()
{
    ASTNodeFactory nodeFactory(*this);
    nodeFactory.markEndPosition();
    return nodeFactory.createNode<Identifier>(expectIdentifierToken());
}

ASTPointer<TypeName> Parser::parseTypeName(bool _allowVar)
{
    ASTPointer<TypeName> type;
    Token::Value token = m_scanner->getCurrentToken();
    if (Token::isElementaryTypeName(token))
    {
        type = ASTNodeFactory(*this).createNode<ElementaryTypeName>(token);
        m_scanner->next();
    }
    else if (token == Token::VAR)
    {
        if (!_allowVar)
            BOOST_THROW_EXCEPTION(createParserError("Expected explicit type name."));
        m_scanner->next();
    }
    else if (token == Token::MAPPING)
    {
        type = parseMapping();
    }
    else if (token == Token::IDENTIFIER)
    {
        ASTNodeFactory nodeFactory(*this);
        nodeFactory.markEndPosition();
        type = nodeFactory.createNode<UserDefinedTypeName>(expectIdentifierToken());
    }
    else
        BOOST_THROW_EXCEPTION(createParserError("Expected type name"));
    return type;
}

ASTPointer<Mapping> Parser::parseMapping()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::MAPPING);
    expectToken(Token::LPAREN);
    if (!Token::isElementaryTypeName(m_scanner->getCurrentToken()))
        BOOST_THROW_EXCEPTION(createParserError("Expected elementary type name for mapping key type"));
    ASTPointer<ElementaryTypeName> keyType;
    keyType = ASTNodeFactory(*this).createNode<ElementaryTypeName>(m_scanner->getCurrentToken());
    m_scanner->next();
    expectToken(Token::ARROW);
    bool const allowVar = false;
    ASTPointer<TypeName> valueType = parseTypeName(allowVar);
    nodeFactory.markEndPosition();
    expectToken(Token::RPAREN);
    return nodeFactory.createNode<Mapping>(keyType, valueType);
}

ASTPointer<ParameterList> Parser::parseParameterList(bool _allowEmpty, bool _allowIndexed)
{
    ASTNodeFactory nodeFactory(*this);
    vector<ASTPointer<VariableDeclaration>> parameters;
    VarDeclParserOptions options;
    options.allowIndexed = _allowIndexed;
    expectToken(Token::LPAREN);
    if (!_allowEmpty || m_scanner->getCurrentToken() != Token::RPAREN)
    {
        parameters.push_back(parseVariableDeclaration(options));
        while (m_scanner->getCurrentToken() != Token::RPAREN)
        {
            expectToken(Token::COMMA);
            parameters.push_back(parseVariableDeclaration(options));
        }
    }
    nodeFactory.markEndPosition();
    m_scanner->next();
    return nodeFactory.createNode<ParameterList>(parameters);
}

ASTPointer<Block> Parser::parseBlock()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::LBRACE);
    vector<ASTPointer<Statement>> statements;
    while (m_scanner->getCurrentToken() != Token::RBRACE)
        statements.push_back(parseStatement());
    nodeFactory.markEndPosition();
    expectToken(Token::RBRACE);
    return nodeFactory.createNode<Block>(statements);
}

ASTPointer<Statement> Parser::parseStatement()
{
    ASTPointer<Statement> statement;
    switch (m_scanner->getCurrentToken())
    {
    case Token::IF:
        return parseIfStatement();
    case Token::WHILE:
        return parseWhileStatement();
    case Token::FOR:
        return parseForStatement();
    case Token::LBRACE:
        return parseBlock();
        // starting from here, all statements must be terminated by a semicolon
    case Token::CONTINUE:
        statement = ASTNodeFactory(*this).createNode<Continue>();
        m_scanner->next();
        break;
    case Token::BREAK:
        statement = ASTNodeFactory(*this).createNode<Break>();
        m_scanner->next();
        break;
    case Token::RETURN:
    {
        ASTNodeFactory nodeFactory(*this);
        ASTPointer<Expression> expression;
        if (m_scanner->next() != Token::SEMICOLON)
        {
            expression = parseExpression();
            nodeFactory.setEndPositionFromNode(expression);
        }
        statement = nodeFactory.createNode<Return>(expression);
        break;
    }
    case Token::IDENTIFIER:
        if (m_insideModifier && m_scanner->getCurrentLiteral() == "_")
        {
            statement = ASTNodeFactory(*this).createNode<PlaceholderStatement>();
            m_scanner->next();
            return statement;
        }
    // fall-through
    default:
        statement = parseVarDefOrExprStmt();
    }
    expectToken(Token::SEMICOLON);
    return statement;
}

ASTPointer<IfStatement> Parser::parseIfStatement()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::IF);
    expectToken(Token::LPAREN);
    ASTPointer<Expression> condition = parseExpression();
    expectToken(Token::RPAREN);
    ASTPointer<Statement> trueBody = parseStatement();
    ASTPointer<Statement> falseBody;
    if (m_scanner->getCurrentToken() == Token::ELSE)
    {
        m_scanner->next();
        falseBody = parseStatement();
        nodeFactory.setEndPositionFromNode(falseBody);
    }
    else
        nodeFactory.setEndPositionFromNode(trueBody);
    return nodeFactory.createNode<IfStatement>(condition, trueBody, falseBody);
}

ASTPointer<WhileStatement> Parser::parseWhileStatement()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::WHILE);
    expectToken(Token::LPAREN);
    ASTPointer<Expression> condition = parseExpression();
    expectToken(Token::RPAREN);
    ASTPointer<Statement> body = parseStatement();
    nodeFactory.setEndPositionFromNode(body);
    return nodeFactory.createNode<WhileStatement>(condition, body);
}

ASTPointer<ForStatement> Parser::parseForStatement()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Statement> initExpression;
    ASTPointer<Expression> conditionExpression;
    ASTPointer<ExpressionStatement> loopExpression;
    expectToken(Token::FOR);
    expectToken(Token::LPAREN);

    // LTODO: Maybe here have some predicate like peekExpression() instead of checking for semicolon and RPAREN?
    if (m_scanner->getCurrentToken() != Token::SEMICOLON)
        initExpression = parseVarDefOrExprStmt();
    expectToken(Token::SEMICOLON);

    if (m_scanner->getCurrentToken() != Token::SEMICOLON)
        conditionExpression = parseExpression();
    expectToken(Token::SEMICOLON);

    if (m_scanner->getCurrentToken() != Token::RPAREN)
        loopExpression = parseExpressionStatement();
    expectToken(Token::RPAREN);

    ASTPointer<Statement> body = parseStatement();
    nodeFactory.setEndPositionFromNode(body);
    return nodeFactory.createNode<ForStatement>(initExpression,
                                                conditionExpression,
                                                loopExpression,
                                                body);
}

ASTPointer<Statement> Parser::parseVarDefOrExprStmt()
{
    if (peekVariableDefinition())
        return parseVariableDefinition();
    else
        return parseExpressionStatement();
}

ASTPointer<VariableDefinition> Parser::parseVariableDefinition()
{
    ASTNodeFactory nodeFactory(*this);
    VarDeclParserOptions options;
    options.allowVar = true;
    ASTPointer<VariableDeclaration> variable = parseVariableDeclaration(options);
    ASTPointer<Expression> value;
    if (m_scanner->getCurrentToken() == Token::ASSIGN)
    {
        m_scanner->next();
        value = parseExpression();
        nodeFactory.setEndPositionFromNode(value);
    }
    else
        nodeFactory.setEndPositionFromNode(variable);
    return nodeFactory.createNode<VariableDefinition>(variable, value);
}

ASTPointer<ExpressionStatement> Parser::parseExpressionStatement()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Expression> expression = parseExpression();
    nodeFactory.setEndPositionFromNode(expression);
    return nodeFactory.createNode<ExpressionStatement>(expression);
}

ASTPointer<Expression> Parser::parseExpression()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Expression> expression = parseBinaryExpression();
    if (!Token::isAssignmentOp(m_scanner->getCurrentToken()))
        return expression;
    Token::Value assignmentOperator = expectAssignmentOperator();
    ASTPointer<Expression> rightHandSide = parseExpression();
    nodeFactory.setEndPositionFromNode(rightHandSide);
    return nodeFactory.createNode<Assignment>(expression, assignmentOperator, rightHandSide);
}

ASTPointer<Expression> Parser::parseBinaryExpression(int _minPrecedence)
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Expression> expression = parseUnaryExpression();
    int precedence = Token::precedence(m_scanner->getCurrentToken());
    for (; precedence >= _minPrecedence; --precedence)
    {
        while (Token::precedence(m_scanner->getCurrentToken()) == precedence)
        {
            Token::Value op = m_scanner->getCurrentToken();
            m_scanner->next();
            ASTPointer<Expression> right = parseBinaryExpression(precedence + 1);
            nodeFactory.setEndPositionFromNode(right);
            expression = nodeFactory.createNode<BinaryOperation>(expression, op, right);
        }
    }
    return expression;
}

ASTPointer<Expression> Parser::parseUnaryExpression()
{
    ASTNodeFactory nodeFactory(*this);
    Token::Value token = m_scanner->getCurrentToken();
    if (Token::isUnaryOp(token) || Token::isCountOp(token))
    {
        // prefix expression
        m_scanner->next();
        ASTPointer<Expression> subExpression = parseUnaryExpression();
        nodeFactory.setEndPositionFromNode(subExpression);
        return nodeFactory.createNode<UnaryOperation>(token, subExpression, true);
    }
    else
    {
        // potential postfix expression
        ASTPointer<Expression> subExpression = parseLeftHandSideExpression();
        token = m_scanner->getCurrentToken();
        if (!Token::isCountOp(token))
            return subExpression;
        nodeFactory.markEndPosition();
        m_scanner->next();
        return nodeFactory.createNode<UnaryOperation>(token, subExpression, false);
    }
}

ASTPointer<Expression> Parser::parseLeftHandSideExpression()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Expression> expression;
    if (m_scanner->getCurrentToken() == Token::NEW)
    {
        expectToken(Token::NEW);
        ASTPointer<Identifier> contractName(parseIdentifier());
        nodeFactory.setEndPositionFromNode(contractName);
        expression = nodeFactory.createNode<NewExpression>(contractName);
    }
    else
        expression = parsePrimaryExpression();

    while (true)
    {
        switch (m_scanner->getCurrentToken())
        {
        case Token::LBRACK:
        {
            m_scanner->next();
            ASTPointer<Expression> index = parseExpression();
            nodeFactory.markEndPosition();
            expectToken(Token::RBRACK);
            expression = nodeFactory.createNode<IndexAccess>(expression, index);
        }
        break;
        case Token::PERIOD:
        {
            m_scanner->next();
            nodeFactory.markEndPosition();
            expression = nodeFactory.createNode<MemberAccess>(expression, expectIdentifierToken());
        }
        break;
        case Token::LPAREN:
        {
            m_scanner->next();
            vector<ASTPointer<Expression>> arguments = parseFunctionCallArguments();
            nodeFactory.markEndPosition();
            expectToken(Token::RPAREN);
            expression = nodeFactory.createNode<FunctionCall>(expression, arguments);
        }
        break;
        default:
            return expression;
        }
    }
}

ASTPointer<Expression> Parser::parsePrimaryExpression()
{
    ASTNodeFactory nodeFactory(*this);
    Token::Value token = m_scanner->getCurrentToken();
    ASTPointer<Expression> expression;
    switch (token)
    {
    case Token::TRUE_LITERAL:
    case Token::FALSE_LITERAL:
        expression = nodeFactory.createNode<Literal>(token, getLiteralAndAdvance());
        break;
    case Token::NUMBER:
    case Token::STRING_LITERAL:
        nodeFactory.markEndPosition();
        expression = nodeFactory.createNode<Literal>(token, getLiteralAndAdvance());
        break;
    case Token::IDENTIFIER:
        nodeFactory.markEndPosition();
        expression = nodeFactory.createNode<Identifier>(getLiteralAndAdvance());
        break;
    case Token::LPAREN:
    {
        m_scanner->next();
        ASTPointer<Expression> expression = parseExpression();
        expectToken(Token::RPAREN);
        return expression;
    }
    default:
        if (Token::isElementaryTypeName(token))
        {
            // used for casts
            expression = nodeFactory.createNode<ElementaryTypeNameExpression>(token);
            m_scanner->next();
        }
        else
        {
            BOOST_THROW_EXCEPTION(createParserError("Expected primary expression."));
            return ASTPointer<Expression>(); // this is not reached
        }
        break;
    }
    return expression;
}

vector<ASTPointer<Expression>> Parser::parseFunctionCallArguments()
{
    vector<ASTPointer<Expression>> arguments;
    if (m_scanner->getCurrentToken() != Token::RPAREN)
    {
        arguments.push_back(parseExpression());
        while (m_scanner->getCurrentToken() != Token::RPAREN)
        {
            expectToken(Token::COMMA);
            arguments.push_back(parseExpression());
        }
    }
    return arguments;
}


bool Parser::peekVariableDefinition()
{
    // distinguish between variable definition (and potentially assignment) and expression statement
    // (which include assignments to other expressions and pre-declared variables)
    // We have a variable definition if we get a keyword that specifies a type name, or
    // in the case of a user-defined type, we have two identifiers following each other.
    return (m_scanner->getCurrentToken() == Token::MAPPING ||
            m_scanner->getCurrentToken() == Token::VAR ||
            ((Token::isElementaryTypeName(m_scanner->getCurrentToken()) ||
              m_scanner->getCurrentToken() == Token::IDENTIFIER) &&
             m_scanner->peekNextToken() == Token::IDENTIFIER));
}

void Parser::expectToken(Token::Value _value)
{
    if (m_scanner->getCurrentToken() != _value)
        BOOST_THROW_EXCEPTION(createParserError(string("Expected token ") + string(Token::getName(_value))));
    m_scanner->next();
}

Token::Value Parser::expectAssignmentOperator()
{
    Token::Value op = m_scanner->getCurrentToken();
    if (!Token::isAssignmentOp(op))
        BOOST_THROW_EXCEPTION(createParserError("Expected assignment operator"));
    m_scanner->next();
    return op;
}

ASTPointer<ASTString> Parser::expectIdentifierToken()
{
    if (m_scanner->getCurrentToken() != Token::IDENTIFIER)
        BOOST_THROW_EXCEPTION(createParserError("Expected identifier"));
    return getLiteralAndAdvance();
}

ASTPointer<ASTString> Parser::getLiteralAndAdvance()
{
    ASTPointer<ASTString> identifier = make_shared<ASTString>(m_scanner->getCurrentLiteral());
    m_scanner->next();
    return identifier;
}

ASTPointer<ParameterList> Parser::createEmptyParameterList()
{
    ASTNodeFactory nodeFactory(*this);
    nodeFactory.setLocationEmpty();
    return nodeFactory.createNode<ParameterList>(vector<ASTPointer<VariableDeclaration>>());
}

ParserError Parser::createParserError(string const& _description) const
{
    return ParserError() << errinfo_sourceLocation(Location(getPosition(), getPosition(), getSourceName()))
                         << errinfo_comment(_description);
}


}
}