path: root/libsolidity/parsing/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 <libevmasm/SourceLocation.h>
#include <libsolidity/parsing/Parser.h>
#include <libsolidity/parsing/Scanner.h>
#include <libsolidity/interface/Exceptions.h>
#include <libsolidity/interface/InterfaceHandler.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.position(), -1, _parser.sourceName()) {}
    ASTNodeFactory(Parser const& _parser, ASTPointer<ASTNode> const& _childNode):
        m_parser(_parser), m_location(_childNode->location()) {}

    void markEndPosition() { m_location.end = m_parser.endPosition(); }
    void setLocation(SourceLocation const& _location) { m_location = _location; }
    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->location().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;
    SourceLocation m_location;
};

ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
{
    try
    {
        m_scanner = _scanner;
        ASTNodeFactory nodeFactory(*this);
        vector<ASTPointer<ASTNode>> nodes;
        while (m_scanner->currentToken() != Token::EOS)
        {
            switch (auto token = m_scanner->currentToken())
            {
            case Token::Import:
                nodes.push_back(parseImportDirective());
                break;
            case Token::Contract:
            case Token::Library:
                nodes.push_back(parseContractDefinition(token == Token::Library));
                break;
            default:
                fatalParserError(std::string("Expected import directive or contract definition."));
            }
        }
        return nodeFactory.createNode<SourceUnit>(nodes);
    }
    catch (FatalError const&)
    {
        if (m_errors.empty())
            throw; // Something is weird here, rather throw again.
        return nullptr;
    }
}

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

int Parser::position() const
{
    return m_scanner->currentLocation().start;
}

int Parser::endPosition() const
{
    return m_scanner->currentLocation().end;
}

ASTPointer<ImportDirective> Parser::parseImportDirective()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::Import);
    if (m_scanner->currentToken() != Token::StringLiteral)
        fatalParserError(std::string("Expected string literal (URL)."));
    ASTPointer<ASTString> url = getLiteralAndAdvance();
    nodeFactory.markEndPosition();
    expectToken(Token::Semicolon);
    return nodeFactory.createNode<ImportDirective>(url);
}

ASTPointer<ContractDefinition> Parser::parseContractDefinition(bool _isLibrary)
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<ASTString> docString;
    if (m_scanner->currentCommentLiteral() != "")
        docString = make_shared<ASTString>(m_scanner->currentCommentLiteral());
    expectToken(_isLibrary ? Token::Library : Token::Contract);
    ASTPointer<ASTString> name = expectIdentifierToken();
    vector<ASTPointer<InheritanceSpecifier>> baseContracts;
    if (m_scanner->currentToken() == Token::Is)
        do
        {
            m_scanner->next();
            baseContracts.push_back(parseInheritanceSpecifier());
        }
        while (m_scanner->currentToken() == Token::Comma);
    vector<ASTPointer<ASTNode>> subNodes;
    expectToken(Token::LBrace);
    while (true)
    {
        Token::Value currentTokenValue= m_scanner->currentToken();
        if (currentTokenValue == Token::RBrace)
            break;
        else if (currentTokenValue == Token::Function)
            subNodes.push_back(parseFunctionDefinition(name.get()));
        else if (currentTokenValue == Token::Struct)
            subNodes.push_back(parseStructDefinition());
        else if (currentTokenValue == Token::Enum)
            subNodes.push_back(parseEnumDefinition());
        else if (
            currentTokenValue == Token::Identifier ||
            currentTokenValue == Token::Mapping ||
            Token::isElementaryTypeName(currentTokenValue)
        )
        {
            VarDeclParserOptions options;
            options.isStateVariable = true;
            options.allowInitialValue = true;
            subNodes.push_back(parseVariableDeclaration(options));
            expectToken(Token::Semicolon);
        }
        else if (currentTokenValue == Token::Modifier)
            subNodes.push_back(parseModifierDefinition());
        else if (currentTokenValue == Token::Event)
            subNodes.push_back(parseEventDefinition());
        else
            fatalParserError(std::string("Function, variable, struct or modifier declaration expected."));
    }
    nodeFactory.markEndPosition();
    expectToken(Token::RBrace);
    return nodeFactory.createNode<ContractDefinition>(
        name,
        docString,
        baseContracts,
        subNodes,
        _isLibrary
    );
}

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

Declaration::Visibility Parser::parseVisibilitySpecifier(Token::Value _token)
{
    Declaration::Visibility visibility(Declaration::Visibility::Default);
    if (_token == Token::Public)
        visibility = Declaration::Visibility::Public;
    else if (_token == Token::Internal)
        visibility = Declaration::Visibility::Internal;
    else if (_token == Token::Private)
        visibility = Declaration::Visibility::Private;
    else if (_token == Token::External)
        visibility = Declaration::Visibility::External;
    else
        solAssert(false, "Invalid visibility specifier.");
    m_scanner->next();
    return visibility;
}

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

    expectToken(Token::Function);
    ASTPointer<ASTString> name;
    if (m_scanner->currentToken() == Token::LParen)
        name = make_shared<ASTString>(); // anonymous function
    else
        name = expectIdentifierToken();
    VarDeclParserOptions options;
    options.allowLocationSpecifier = true;
    ASTPointer<ParameterList> parameters(parseParameterList(options));
    bool isDeclaredConst = false;
    Declaration::Visibility visibility(Declaration::Visibility::Default);
    vector<ASTPointer<ModifierInvocation>> modifiers;
    while (true)
    {
        Token::Value token = m_scanner->currentToken();
        if (token == Token::Const)
        {
            isDeclaredConst = true;
            m_scanner->next();
        }
        else if (token == Token::Identifier)
            modifiers.push_back(parseModifierInvocation());
        else if (Token::isVisibilitySpecifier(token))
        {
            if (visibility != Declaration::Visibility::Default)
                fatalParserError(std::string("Multiple visibility specifiers."));
            visibility = parseVisibilitySpecifier(token);
        }
        else
            break;
    }
    ASTPointer<ParameterList> returnParameters;
    if (m_scanner->currentToken() == Token::Returns)
    {
        bool const permitEmptyParameterList = false;
        m_scanner->next();
        returnParameters = parseParameterList(options, permitEmptyParameterList);
    }
    else
        returnParameters = createEmptyParameterList();
    ASTPointer<Block> block = ASTPointer<Block>();
    nodeFactory.markEndPosition();
    if (m_scanner->currentToken() != Token::Semicolon)
    {
        block = parseBlock();
        nodeFactory.setEndPositionFromNode(block);
    }
    else
        m_scanner->next(); // just consume the ';'
    bool const c_isConstructor = (_contractName && *name == *_contractName);
    return nodeFactory.createNode<FunctionDefinition>(
        name,
        visibility,
        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->currentToken() != Token::RBrace)
    {
        members.push_back(parseVariableDeclaration());
        expectToken(Token::Semicolon);
    }
    nodeFactory.markEndPosition();
    expectToken(Token::RBrace);
    return nodeFactory.createNode<StructDefinition>(name, members);
}

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

ASTPointer<EnumDefinition> Parser::parseEnumDefinition()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::Enum);
    ASTPointer<ASTString> name = expectIdentifierToken();
    vector<ASTPointer<EnumValue>> members;
    expectToken(Token::LBrace);

    while (m_scanner->currentToken() != Token::RBrace)
    {
        members.push_back(parseEnumValue());
        if (m_scanner->currentToken() == Token::RBrace)
            break;
        expectToken(Token::Comma);
        if (m_scanner->currentToken() != Token::Identifier)
            fatalParserError(std::string("Expected Identifier after ','"));
    }

    nodeFactory.markEndPosition();
    expectToken(Token::RBrace);
    return nodeFactory.createNode<EnumDefinition>(name, members);
}

ASTPointer<VariableDeclaration> Parser::parseVariableDeclaration(
    VarDeclParserOptions const& _options,
    ASTPointer<TypeName> const& _lookAheadArrayType
)
{
    ASTNodeFactory nodeFactory = _lookAheadArrayType ?
        ASTNodeFactory(*this, _lookAheadArrayType) : ASTNodeFactory(*this);
    ASTPointer<TypeName> type;
    if (_lookAheadArrayType)
        type = _lookAheadArrayType;
    else
    {
        type = parseTypeName(_options.allowVar);
        if (type != nullptr)
            nodeFactory.setEndPositionFromNode(type);
    }
    bool isIndexed = false;
    bool isDeclaredConst = false;
    Declaration::Visibility visibility(Declaration::Visibility::Default);
    VariableDeclaration::Location location = VariableDeclaration::Location::Default;
    ASTPointer<ASTString> identifier;

    while (true)
    {
        Token::Value token = m_scanner->currentToken();
        if (_options.isStateVariable && Token::isVariableVisibilitySpecifier(token))
        {
            if (visibility != Declaration::Visibility::Default)
                fatalParserError(std::string("Visibility already specified."));
            visibility = parseVisibilitySpecifier(token);
        }
        else
        {
            if (_options.allowIndexed && token == Token::Indexed)
                isIndexed = true;
            else if (token == Token::Const)
                isDeclaredConst = true;
            else if (_options.allowLocationSpecifier && Token::isLocationSpecifier(token))
            {
                if (location != VariableDeclaration::Location::Default)
                    fatalParserError(std::string("Location already specified."));
                if (!type)
                    fatalParserError(std::string("Location specifier needs explicit type name."));
                location = (
                    token == Token::Memory ?
                    VariableDeclaration::Location::Memory :
                    VariableDeclaration::Location::Storage
                );
            }
            else
                break;
            m_scanner->next();
        }
    }
    nodeFactory.markEndPosition();

    if (_options.allowEmptyName && m_scanner->currentToken() != Token::Identifier)
    {
        identifier = make_shared<ASTString>("");
        solAssert(type != nullptr, "");
        nodeFactory.setEndPositionFromNode(type);
    }
    else
        identifier = expectIdentifierToken();
    ASTPointer<Expression> value;
    if (_options.allowInitialValue)
    {
        if (m_scanner->currentToken() == Token::Assign)
        {
            m_scanner->next();
            value = parseExpression();
            nodeFactory.setEndPositionFromNode(value);
        }
    }
    return nodeFactory.createNode<VariableDeclaration>(
        type,
        identifier,
        value,
        visibility,
        _options.isStateVariable,
        isIndexed,
        isDeclaredConst,
        location
    );
}

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

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

    expectToken(Token::Modifier);
    ASTPointer<ASTString> name(expectIdentifierToken());
    ASTPointer<ParameterList> parameters;
    if (m_scanner->currentToken() == Token::LParen)
    {
        VarDeclParserOptions options;
        options.allowIndexed = true;
        options.allowLocationSpecifier = true;
        parameters = parseParameterList(options);
    }
    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->currentCommentLiteral() != "")
        docstring = make_shared<ASTString>(m_scanner->currentCommentLiteral());

    expectToken(Token::Event);
    ASTPointer<ASTString> name(expectIdentifierToken());
    ASTPointer<ParameterList> parameters;
    if (m_scanner->currentToken() == Token::LParen)
    {
        VarDeclParserOptions options;
        options.allowIndexed = true;
        parameters = parseParameterList(options);
    }
    else
        parameters = createEmptyParameterList();
    bool anonymous = false;
    if (m_scanner->currentToken() == Token::Anonymous)
    {
        anonymous = true;
        m_scanner->next();
    }
    nodeFactory.markEndPosition();
    expectToken(Token::Semicolon);
    return nodeFactory.createNode<EventDefinition>(name, docstring, parameters, anonymous);
}

ASTPointer<ModifierInvocation> Parser::parseModifierInvocation()
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<Identifier> name(parseIdentifier());
    vector<ASTPointer<Expression>> arguments;
    if (m_scanner->currentToken() == Token::LParen)
    {
        m_scanner->next();
        arguments = parseFunctionCallListArguments();
        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)
{
    ASTNodeFactory nodeFactory(*this);
    ASTPointer<TypeName> type;
    Token::Value token = m_scanner->currentToken();
    if (Token::isElementaryTypeName(token))
    {
        type = ASTNodeFactory(*this).createNode<ElementaryTypeName>(token);
        m_scanner->next();
    }
    else if (token == Token::Var)
    {
        if (!_allowVar)
            fatalParserError(std::string("Expected explicit type name."));
        m_scanner->next();
    }
    else if (token == Token::Mapping)
        type = parseMapping();
    else if (token == Token::Identifier)
    {
        ASTNodeFactory nodeFactory(*this);
        nodeFactory.markEndPosition();
        vector<ASTString> identifierPath{*expectIdentifierToken()};
        while (m_scanner->currentToken() == Token::Period)
        {
            m_scanner->next();
            nodeFactory.markEndPosition();
            identifierPath.push_back(*expectIdentifierToken());
        }
        type = nodeFactory.createNode<UserDefinedTypeName>(identifierPath);
    }
    else
        fatalParserError(std::string("Expected type name"));

    if (type)
        // Parse "[...]" postfixes for arrays.
        while (m_scanner->currentToken() == Token::LBrack)
        {
            m_scanner->next();
            ASTPointer<Expression> length;
            if (m_scanner->currentToken() != Token::RBrack)
                length = parseExpression();
            nodeFactory.markEndPosition();
            expectToken(Token::RBrack);
            type = nodeFactory.createNode<ArrayTypeName>(type, length);
        }
    return type;
}

ASTPointer<Mapping> Parser::parseMapping()
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::Mapping);
    expectToken(Token::LParen);
    if (!Token::isElementaryTypeName(m_scanner->currentToken()))
        fatalParserError(std::string("Expected elementary type name for mapping key type"));
    ASTPointer<ElementaryTypeName> keyType;
    keyType = ASTNodeFactory(*this).createNode<ElementaryTypeName>(m_scanner->currentToken());
    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(
    VarDeclParserOptions const& _options,
    bool _allowEmpty
)
{
    ASTNodeFactory nodeFactory(*this);
    vector<ASTPointer<VariableDeclaration>> parameters;
    VarDeclParserOptions options(_options);
    options.allowEmptyName = true;
    expectToken(Token::LParen);
    if (!_allowEmpty || m_scanner->currentToken() != Token::RParen)
    {
        parameters.push_back(parseVariableDeclaration(options));
        while (m_scanner->currentToken() != Token::RParen)
        {
            expectToken(Token::Comma);
            parameters.push_back(parseVariableDeclaration(options));
        }
    }
    nodeFactory.markEndPosition();
    m_scanner->next();
    return nodeFactory.createNode<ParameterList>(parameters);
}

ASTPointer<Block> Parser::parseBlock(ASTPointer<ASTString> const& _docString)
{
    ASTNodeFactory nodeFactory(*this);
    expectToken(Token::LBrace);
    vector<ASTPointer<Statement>> statements;
    while (m_scanner->currentToken() != Token::RBrace)
        statements.push_back(parseStatement());
    nodeFactory.markEndPosition();
    expectToken(Token::RBrace);
    return nodeFactory.createNode<Block>(_docString, statements);
}

ASTPointer<Statement> Parser::parseStatement()
{
    ASTPointer<ASTString> docString;
    if (m_scanner->currentCommentLiteral() != "")
        docString = make_shared<ASTString>(m_scanner->currentCommentLiteral());
    ASTPointer<Statement> statement;
    switch (m_scanner->currentToken())
    {
    case Token::If:
        return parseIfStatement(docString);
    case Token::While:
        return parseWhileStatement(docString);
    case Token::For:
        return parseForStatement(docString);
    case Token::LBrace:
        return parseBlock(docString);
        // starting from here, all statements must be terminated by a semicolon
    case Token::Continue:
        statement = ASTNodeFactory(*this).createNode<Continue>(docString);
        m_scanner->next();
        break;
    case Token::Break:
        statement = ASTNodeFactory(*this).createNode<Break>(docString);
        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>(docString, expression);
        break;
    }
    case Token::Throw:
    {
        statement = ASTNodeFactory(*this).createNode<Throw>(docString);
        m_scanner->next();
        break;
    }
    case Token::Identifier:
        if (m_insideModifier && m_scanner->currentLiteral() == "_")
        {
            statement = ASTNodeFactory(*this).createNode<PlaceholderStatement>(docString);
            m_scanner->next();
            return statement;
        }
    // fall-through
    default:
        statement = parseSimpleStatement(docString);
    }
    expectToken(Token::Semicolon);
    return statement;
}

ASTPointer<IfStatement> Parser::parseIfStatement(ASTPointer<ASTString> const& _docString)
{
    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->currentToken() == Token::Else)
    {
        m_scanner->next();
        falseBody = parseStatement();
        nodeFactory.setEndPositionFromNode(falseBody);
    }
    else
        nodeFactory.setEndPositionFromNode(trueBody);
    return nodeFactory.createNode<IfStatement>(_docString, condition, trueBody, falseBody);
}

ASTPointer<WhileStatement> Parser::parseWhileStatement(ASTPointer<ASTString> const& _docString)
{
    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>(_docString, condition, body);
}

ASTPointer<ForStatement> Parser::parseForStatement(ASTPointer<ASTString> const& _docString)
{
    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->currentToken() != Token::Semicolon)
        initExpression = parseSimpleStatement(ASTPointer<ASTString>());
    expectToken(Token::Semicolon);

    if (m_scanner->currentToken() != Token::Semicolon)
        conditionExpression = parseExpression();
    expectToken(Token::Semicolon);

    if (m_scanner->currentToken() != Token::RParen)
        loopExpression = parseExpressionStatement(ASTPointer<ASTString>());
    expectToken(Token::RParen);

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

ASTPointer<Statement> Parser::parseSimpleStatement(ASTPointer<ASTString> const& _docString)
{
    // These two cases are very hard to distinguish:
    // x[7 * 20 + 3] a;  -  x[7 * 20 + 3] = 9;
    // In the first case, x is a type name, in the second it is the name of a variable.
    // As an extension, we can even have:
    // `x.y.z[1][2] a;` and `x.y.z[1][2] = 10;`
    // Where in the first, x.y.z leads to a type name where in the second, it accesses structs.
    switch (peekStatementType())
    {
    case LookAheadInfo::VariableDeclarationStatement:
        return parseVariableDeclarationStatement(_docString);
    case LookAheadInfo::ExpressionStatement:
        return parseExpressionStatement(_docString);
    default:
        break;
    }

    // At this point, we have 'Identifier "["' or 'Identifier "." Identifier' or 'ElementoryTypeName "["'.
    // We parse '(Identifier ("." Identifier)* |ElementaryTypeName) ( "[" Expression "]" )+'
    // until we can decide whether to hand this over to ExpressionStatement or create a
    // VariableDeclarationStatement out of it.

    vector<ASTPointer<PrimaryExpression>> path;
    bool startedWithElementary = false;
    if (m_scanner->currentToken() == Token::Identifier)
        path.push_back(parseIdentifier());
    else
    {
        startedWithElementary = true;
        path.push_back(ASTNodeFactory(*this).createNode<ElementaryTypeNameExpression>(m_scanner->currentToken()));
        m_scanner->next();
    }
    while (!startedWithElementary && m_scanner->currentToken() == Token::Period)
    {
        m_scanner->next();
        path.push_back(parseIdentifier());
    }
    vector<pair<ASTPointer<Expression>, SourceLocation>> indices;
    while (m_scanner->currentToken() == Token::LBrack)
    {
        expectToken(Token::LBrack);
        ASTPointer<Expression> index;
        if (m_scanner->currentToken() != Token::RBrack)
            index = parseExpression();
        SourceLocation indexLocation = path.front()->location();
        indexLocation.end = endPosition();
        indices.push_back(make_pair(index, indexLocation));
        expectToken(Token::RBrack);
    }

    if (m_scanner->currentToken() == Token::Identifier || Token::isLocationSpecifier(m_scanner->currentToken()))
        return parseVariableDeclarationStatement(_docString, typeNameIndexAccessStructure(path, indices));
    else
        return parseExpressionStatement(_docString, expressionFromIndexAccessStructure(path, indices));
}

ASTPointer<VariableDeclarationStatement> Parser::parseVariableDeclarationStatement(
    ASTPointer<ASTString> const& _docString,
    ASTPointer<TypeName> const& _lookAheadArrayType
)
{
    ASTNodeFactory nodeFactory(*this);
    if (_lookAheadArrayType)
        nodeFactory.setLocation(_lookAheadArrayType->location());
    vector<ASTPointer<VariableDeclaration>> variables;
    ASTPointer<Expression> value;
    if (
        !_lookAheadArrayType &&
        m_scanner->currentToken() == Token::Var &&
        m_scanner->peekNextToken() == Token::LParen
    )
    {
        // Parse `var (a, b, ,, c) = ...` into a single VariableDeclarationStatement with multiple variables.
        m_scanner->next();
        m_scanner->next();
        if (m_scanner->currentToken() != Token::RParen)
            while (true)
            {
                ASTPointer<VariableDeclaration> var;
                if (
                    m_scanner->currentToken() != Token::Comma &&
                    m_scanner->currentToken() != Token::RParen
                )
                {
                    ASTNodeFactory varDeclNodeFactory(*this);
                    varDeclNodeFactory.markEndPosition();
                    ASTPointer<ASTString> name = expectIdentifierToken();
                    var = varDeclNodeFactory.createNode<VariableDeclaration>(
                        ASTPointer<TypeName>(),
                        name,
                        ASTPointer<Expression>(),
                        VariableDeclaration::Visibility::Default
                    );
                }
                variables.push_back(var);
                if (m_scanner->currentToken() == Token::RParen)
                    break;
                else
                    expectToken(Token::Comma);
            }
        nodeFactory.markEndPosition();
        m_scanner->next();
    }
    else
    {
        VarDeclParserOptions options;
        options.allowVar = true;
        options.allowLocationSpecifier = true;
        variables.push_back(parseVariableDeclaration(options, _lookAheadArrayType));
    }
    if (m_scanner->currentToken() == Token::Assign)
    {
        m_scanner->next();
        value = parseExpression();
        nodeFactory.setEndPositionFromNode(value);
    }
    return nodeFactory.createNode<VariableDeclarationStatement>(_docString, variables, value);
}

ASTPointer<ExpressionStatement> Parser::parseExpressionStatement(
    ASTPointer<ASTString> const& _docString,
    ASTPointer<Expression> const& _lookAheadIndexAccessStructure
)
{
    ASTPointer<Expression> expression = parseExpression(_lookAheadIndexAccessStructure);
    return ASTNodeFactory(*this, expression).createNode<ExpressionStatement>(_docString, expression);
}

ASTPointer<Expression> Parser::parseExpression(
    ASTPointer<Expression> const& _lookAheadIndexAccessStructure
)
{
    ASTPointer<Expression> expression = parseBinaryExpression(4, _lookAheadIndexAccessStructure);
    if (!Token::isAssignmentOp(m_scanner->currentToken()))
        return expression;
    Token::Value assignmentOperator = expectAssignmentOperator();
    ASTPointer<Expression> rightHandSide = parseExpression();
    ASTNodeFactory nodeFactory(*this, expression);
    nodeFactory.setEndPositionFromNode(rightHandSide);
    return nodeFactory.createNode<Assignment>(expression, assignmentOperator, rightHandSide);
}

ASTPointer<Expression> Parser::parseBinaryExpression(
    int _minPrecedence,
    ASTPointer<Expression> const& _lookAheadIndexAccessStructure
)
{
    ASTPointer<Expression> expression = parseUnaryExpression(_lookAheadIndexAccessStructure);
    ASTNodeFactory nodeFactory(*this, expression);
    int precedence = Token::precedence(m_scanner->currentToken());
    for (; precedence >= _minPrecedence; --precedence)
        while (Token::precedence(m_scanner->currentToken()) == precedence)
        {
            Token::Value op = m_scanner->currentToken();
            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(
    ASTPointer<Expression> const& _lookAheadIndexAccessStructure
)
{
    ASTNodeFactory nodeFactory = _lookAheadIndexAccessStructure ?
        ASTNodeFactory(*this, _lookAheadIndexAccessStructure) : ASTNodeFactory(*this);
    Token::Value token = m_scanner->currentToken();
    if (!_lookAheadIndexAccessStructure && (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(_lookAheadIndexAccessStructure);
        token = m_scanner->currentToken();
        if (!Token::isCountOp(token))
            return subExpression;
        nodeFactory.markEndPosition();
        m_scanner->next();
        return nodeFactory.createNode<UnaryOperation>(token, subExpression, false);
    }
}

ASTPointer<Expression> Parser::parseLeftHandSideExpression(
    ASTPointer<Expression> const& _lookAheadIndexAccessStructure
)
{
    ASTNodeFactory nodeFactory = _lookAheadIndexAccessStructure ?
        ASTNodeFactory(*this, _lookAheadIndexAccessStructure) : ASTNodeFactory(*this);

    ASTPointer<Expression> expression;
    if (_lookAheadIndexAccessStructure)
        expression = _lookAheadIndexAccessStructure;
    else if (m_scanner->currentToken() == Token::New)
    {
        expectToken(Token::New);
        ASTPointer<TypeName> contractName(parseTypeName(false));
        nodeFactory.setEndPositionFromNode(contractName);
        expression = nodeFactory.createNode<NewExpression>(contractName);
    }
    else
        expression = parsePrimaryExpression();

    while (true)
    {
        switch (m_scanner->currentToken())
        {
        case Token::LBrack:
        {
            m_scanner->next();
            ASTPointer<Expression> index;
            if (m_scanner->currentToken() != Token::RBrack)
                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;
            vector<ASTPointer<ASTString>> names;
            std::tie(arguments, names) = parseFunctionCallArguments();
            nodeFactory.markEndPosition();
            expectToken(Token::RParen);
            expression = nodeFactory.createNode<FunctionCall>(expression, arguments, names);
        }
        break;
        default:
            return expression;
        }
    }
}

ASTPointer<Expression> Parser::parsePrimaryExpression()
{
    ASTNodeFactory nodeFactory(*this);
    Token::Value token = m_scanner->currentToken();
    ASTPointer<Expression> expression;
    switch (token)
    {
    case Token::TrueLiteral:
    case Token::FalseLiteral:
        expression = nodeFactory.createNode<Literal>(token, getLiteralAndAdvance());
        break;
    case Token::Number:
        if (Token::isEtherSubdenomination(m_scanner->peekNextToken()))
        {
            ASTPointer<ASTString> literal = getLiteralAndAdvance();
            nodeFactory.markEndPosition();
            Literal::SubDenomination subdenomination = static_cast<Literal::SubDenomination>(m_scanner->currentToken());
            m_scanner->next();
            expression = nodeFactory.createNode<Literal>(token, literal, subdenomination);
            break;
        }
        if (Token::isTimeSubdenomination(m_scanner->peekNextToken()))
        {
            ASTPointer<ASTString> literal = getLiteralAndAdvance();
            nodeFactory.markEndPosition();
            Literal::SubDenomination subdenomination = static_cast<Literal::SubDenomination>(m_scanner->currentToken());
            m_scanner->next();
            expression = nodeFactory.createNode<Literal>(token, literal, subdenomination);
            break;
        }
        // fall-through
    case Token::StringLiteral:
        nodeFactory.markEndPosition();
        expression = nodeFactory.createNode<Literal>(token, getLiteralAndAdvance());
        break;
    case Token::Identifier:
        nodeFactory.markEndPosition();
        expression = nodeFactory.createNode<Identifier>(getLiteralAndAdvance());
        break;
    case Token::LParen:
    {
        // Tuple or parenthesized expression.
        // Special cases: () is empty tuple type, (x) is not a real tuple, (x,) is one-dimensional tuple
        m_scanner->next();
        vector<ASTPointer<Expression>> components;
        if (m_scanner->currentToken() != Token::RParen)
            while (true)
            {
                if (m_scanner->currentToken() != Token::Comma && m_scanner->currentToken() != Token::RParen)
                    components.push_back(parseExpression());
                else
                    components.push_back(ASTPointer<Expression>());
                if (m_scanner->currentToken() == Token::RParen)
                    break;
                else if (m_scanner->currentToken() == Token::Comma)
                    m_scanner->next();
            }
        nodeFactory.markEndPosition();
        expectToken(Token::RParen);
        return nodeFactory.createNode<TupleExpression>(components);
    }
    default:
        if (Token::isElementaryTypeName(token))
        {
            // used for casts
            expression = nodeFactory.createNode<ElementaryTypeNameExpression>(token);
            m_scanner->next();
        }
        else
            fatalParserError(std::string("Expected primary expression."));
        break;
    }
    return expression;
}

vector<ASTPointer<Expression>> Parser::parseFunctionCallListArguments()
{
    vector<ASTPointer<Expression>> arguments;
    if (m_scanner->currentToken() != Token::RParen)
    {
        arguments.push_back(parseExpression());
        while (m_scanner->currentToken() != Token::RParen)
        {
            expectToken(Token::Comma);
            arguments.push_back(parseExpression());
        }
    }
    return arguments;
}

pair<vector<ASTPointer<Expression>>, vector<ASTPointer<ASTString>>> Parser::parseFunctionCallArguments()
{
    pair<vector<ASTPointer<Expression>>, vector<ASTPointer<ASTString>>> ret;
    Token::Value token = m_scanner->currentToken();
    if (token == Token::LBrace)
    {
        // call({arg1 : 1, arg2 : 2 })
        expectToken(Token::LBrace);
        while (m_scanner->currentToken() != Token::RBrace)
        {
            ret.second.push_back(expectIdentifierToken());
            expectToken(Token::Colon);
            ret.first.push_back(parseExpression());

            if (m_scanner->currentToken() == Token::Comma)
                expectToken(Token::Comma);
            else
                break;
        }
        expectToken(Token::RBrace);
    }
    else
        ret.first = parseFunctionCallListArguments();
    return ret;
}

Parser::LookAheadInfo Parser::peekStatementType() const
{
    // Distinguish between variable declaration (and potentially assignment) and expression statement
    // (which include assignments to other expressions and pre-declared variables).
    // We have a variable declaration if we get a keyword that specifies a type name.
    // If it is an identifier or an elementary type name followed by an identifier, we also have
    // a variable declaration.
    // If we get an identifier followed by a "[" or ".", it can be both ("lib.type[9] a;" or "variable.el[9] = 7;").
    // In all other cases, we have an expression statement.
    Token::Value token(m_scanner->currentToken());
    bool mightBeTypeName = (Token::isElementaryTypeName(token) || token == Token::Identifier);

    if (token == Token::Mapping || token == Token::Var)
        return LookAheadInfo::VariableDeclarationStatement;
    if (mightBeTypeName)
    {
        Token::Value next = m_scanner->peekNextToken();
        if (next == Token::Identifier || Token::isLocationSpecifier(next))
            return LookAheadInfo::VariableDeclarationStatement;
        if (next == Token::LBrack || next == Token::Period)
            return LookAheadInfo::IndexAccessStructure;
    }
    return LookAheadInfo::ExpressionStatement;
}

ASTPointer<TypeName> Parser::typeNameIndexAccessStructure(
    vector<ASTPointer<PrimaryExpression>> const& _path,
    vector<pair<ASTPointer<Expression>, SourceLocation>> const& _indices
)
{
    solAssert(!_path.empty(), "");
    ASTNodeFactory nodeFactory(*this);
    SourceLocation location = _path.front()->location();
    location.end = _path.back()->location().end;
    nodeFactory.setLocation(location);

    ASTPointer<TypeName> type;
    if (auto typeName = dynamic_cast<ElementaryTypeNameExpression const*>(_path.front().get()))
    {
        solAssert(_path.size() == 1, "");
        type = nodeFactory.createNode<ElementaryTypeName>(typeName->typeToken());
    }
    else
    {
        vector<ASTString> path;
        for (auto const& el: _path)
            path.push_back(dynamic_cast<Identifier const&>(*el).name());
        type = nodeFactory.createNode<UserDefinedTypeName>(path);
    }
    for (auto const& lengthExpression: _indices)
    {
        nodeFactory.setLocation(lengthExpression.second);
        type = nodeFactory.createNode<ArrayTypeName>(type, lengthExpression.first);
    }
    return type;
}

ASTPointer<Expression> Parser::expressionFromIndexAccessStructure(
    vector<ASTPointer<PrimaryExpression>> const& _path,
    vector<pair<ASTPointer<Expression>, SourceLocation>> const& _indices
)
{
    solAssert(!_path.empty(), "");
    ASTNodeFactory nodeFactory(*this, _path.front());
    ASTPointer<Expression> expression(_path.front());
    for (size_t i = 1; i < _path.size(); ++i)
    {
        SourceLocation location(_path.front()->location());
        location.end = _path[i]->location().end;
        nodeFactory.setLocation(location);
        Identifier const& identifier = dynamic_cast<Identifier const&>(*_path[i]);
        expression = nodeFactory.createNode<MemberAccess>(
            expression,
            make_shared<ASTString>(identifier.name())
        );
    }
    for (auto const& index: _indices)
    {
        nodeFactory.setLocation(index.second);
        expression = nodeFactory.createNode<IndexAccess>(expression, index.first);
    }
    return expression;
}

void Parser::expectToken(Token::Value _value)
{
    if (m_scanner->currentToken() != _value)
        fatalParserError(
            string("Expected token ") +
            string(Token::name(_value)) +
            string(" got '") +
            string(Token::name(m_scanner->currentToken())) +
            string("'")
        );
    m_scanner->next();
}

Token::Value Parser::expectAssignmentOperator()
{
    Token::Value op = m_scanner->currentToken();
    if (!Token::isAssignmentOp(op))
        fatalParserError(
            std::string("Expected assignment operator ") +
            string(" got '") +
            string(Token::name(m_scanner->currentToken())) +
            string("'")
        );
    m_scanner->next();
    return op;
}

ASTPointer<ASTString> Parser::expectIdentifierToken()
{
    if (m_scanner->currentToken() != Token::Identifier)
        fatalParserError(
            std::string("Expected identifier ") +
            string(" got '") +
            string(Token::name(m_scanner->currentToken())) +
            string("'")
        );
    return getLiteralAndAdvance();
}

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

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

void Parser::parserError(string const& _description)
{
    auto err = make_shared<Error>(Error::Type::ParserError);
    *err <<
        errinfo_sourceLocation(SourceLocation(position(), position(), sourceName())) <<
        errinfo_comment(_description);

    m_errors.push_back(err);
}

void Parser::fatalParserError(string const& _description)
{
    parserError(_description);
    BOOST_THROW_EXCEPTION(FatalError());
}

}
}