path: root/libsolidity/formal/Why3Translator.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 2015
 * Component that translates Solidity code into the why3 programming language.
 */

#include <libsolidity/formal/Why3Translator.h>

using namespace std;
using namespace dev;
using namespace dev::solidity;

bool Why3Translator::process(SourceUnit const& _source)
{
    try
    {
        m_indentation = 0;
        if (!m_result.empty())
            fatalError(_source, "Multiple source units not yet supported");
        appendPreface();
        _source.accept(*this);
    }
    catch (FatalError& _e)
    {
        solAssert(m_errorOccured, "");
    }
    return !m_errorOccured;
}

void Why3Translator::error(ASTNode const& _node, string const& _description)
{
    auto err = make_shared<Error>(Error::Type::Why3TranslatorError);
    *err <<
        errinfo_sourceLocation(_node.location()) <<
        errinfo_comment(_description);
    m_errors.push_back(err);
    m_errorOccured = true;
}

void Why3Translator::fatalError(ASTNode const& _node, string const& _description)
{
    error(_node, _description);
    BOOST_THROW_EXCEPTION(FatalError());
}

void Why3Translator::appendPreface()
{
    m_result += R"(
module UInt256
    use import mach.int.Unsigned
    type uint256
    constant max_uint256: int = 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
    clone export mach.int.Unsigned with
        type t = uint256,
        constant max = max_uint256
end
)";
}

string Why3Translator::toFormalType(Type const& _type) const
{
    if (auto type = dynamic_cast<IntegerType const*>(&_type))
    {
        if (!type->isAddress() && !type->isSigned() && type->numBits() == 256)
            return "uint256";
    }
    else if (auto type = dynamic_cast<ArrayType const*>(&_type))
        if (!type->isByteArray() && type->isDynamicallySized() && type->dataStoredIn(DataLocation::Memory))
        {
            string base = toFormalType(*type->baseType());
            if (!base.empty())
                return "array " + base;
        }

    return "";
}

void Why3Translator::addLine(string const& _line)
{
    newLine();
    add(_line);
    newLine();
}

void Why3Translator::add(string const& _str)
{
    if (m_currentLine.empty())
        m_indentationAtLineStart = m_indentation;
    m_currentLine += _str;
}

void Why3Translator::newLine()
{
    if (!m_currentLine.empty())
    {
        for (size_t i = 0; i < m_indentationAtLineStart; ++i)
            m_result.push_back('\t');
        m_result += m_currentLine;
        m_result.push_back('\n');
        m_currentLine.clear();
    }
}

void Why3Translator::unindent()
{
    newLine();
    solAssert(m_indentation > 0, "");
    m_indentation--;
}

bool Why3Translator::visit(ContractDefinition const& _contract)
{
    if (m_seenContract)
        error(_contract, "More than one contract not supported.");
    m_seenContract = true;
    if (_contract.isLibrary())
        error(_contract, "Libraries not supported.");

    addLine("module Contract_" + _contract.name());
    indent();
    addLine("use import int.Int");
    addLine("use import ref.Ref");
    addLine("use import map.Map");
    addLine("use import array.Array");
    addLine("use import int.ComputerDivision");
    addLine("use import mach.int.Unsigned");
    addLine("use import UInt256");
    addLine("exception Ret");

    addLine("type state = {");
    indent();
    m_stateVariables = &_contract.stateVariables();
    for (auto const& variable: _contract.stateVariables())
    {
        string varType = toFormalType(*variable->annotation().type);
        if (varType.empty())
            fatalError(*variable, "Type not supported.");
        addLine("mutable _" + variable->name() + ": ref " + varType);
    }
    unindent();
    addLine("}");

    if (!_contract.baseContracts().empty())
        error(*_contract.baseContracts().front(), "Inheritance not supported.");
    if (!_contract.definedStructs().empty())
        error(*_contract.definedStructs().front(), "User-defined types not supported.");
    if (!_contract.definedEnums().empty())
        error(*_contract.definedEnums().front(), "User-defined types not supported.");
    if (!_contract.events().empty())
        error(*_contract.events().front(), "Events not supported.");
    if (!_contract.functionModifiers().empty())
        error(*_contract.functionModifiers().front(), "Modifiers not supported.");

    ASTNode::listAccept(_contract.definedFunctions(), *this);

    return false;
}

void Why3Translator::endVisit(ContractDefinition const& _contract)
{
    m_stateVariables = nullptr;
    addSourceFromDocStrings(_contract.annotation());
    unindent();
    addLine("end");
}

bool Why3Translator::visit(FunctionDefinition const& _function)
{
    if (!_function.isImplemented())
    {
        error(_function, "Unimplemented functions not supported.");
        return false;
    }
    if (_function.name().empty())
    {
        error(_function, "Fallback functions not supported.");
        return false;
    }
    if (!_function.modifiers().empty())
    {
        error(_function, "Modifiers not supported.");
        return false;
    }

    add("let rec _" + _function.name());
    add(" (state: state)");
    for (auto const& param: _function.parameters())
    {
        string paramType = toFormalType(*param->annotation().type);
        if (paramType.empty())
            error(*param, "Parameter type not supported.");
        if (param->name().empty())
            error(*param, "Anonymous function parameters not supported.");
        add(" (arg_" + param->name() + ": " + paramType + ")");
    }
    add(":");

    indent();
    indent();
    string retString = "(";
    for (auto const& retParam: _function.returnParameters())
    {
        string paramType = toFormalType(*retParam->annotation().type);
        if (paramType.empty())
            error(*retParam, "Parameter type not supported.");
        if (retString.size() != 1)
            retString += ", ";
        retString += paramType;
    }
    add(retString + ")");
    unindent();

    addSourceFromDocStrings(_function.annotation());

    addLine("=");

    // initialise local variables
    for (auto const& variable: _function.parameters())
        addLine("let _" + variable->name() + " = ref arg_" + variable->name() + " in");
    for (auto const& variable: _function.returnParameters())
    {
        if (variable->name().empty())
            error(*variable, "Unnamed return variables not yet supported.");
        string varType = toFormalType(*variable->annotation().type);
        addLine("let _" + variable->name() + ": ref " + varType + " = ref (of_int 0) in");
    }
    for (VariableDeclaration const* variable: _function.localVariables())
    {
        if (variable->name().empty())
            error(*variable, "Unnamed variables not yet supported.");
        string varType = toFormalType(*variable->annotation().type);
        addLine("let _" + variable->name() + ": ref " + varType + " = ref (of_int 0) in");
    }
    addLine("try");

    _function.body().accept(*this);
    add(";");
    addLine("raise Ret");

    string retVals;
    for (auto const& variable: _function.returnParameters())
    {
        if (!retVals.empty())
            retVals += ", ";
        retVals += "!_" + variable->name();
    }
    addLine("with Ret -> (" + retVals + ")");
    newLine();
    unindent();
    addLine("end");
    addLine("");
    return false;
}

bool Why3Translator::visit(Block const& _node)
{
    addSourceFromDocStrings(_node.annotation());
    add("begin");
    indent();
    for (size_t i = 0; i < _node.statements().size(); ++i)
    {
        _node.statements()[i]->accept(*this);
        if (!m_currentLine.empty() && i != _node.statements().size() - 1)
            add(";");
        newLine();
    }
    unindent();
    add("end");
    return false;
}

bool Why3Translator::visit(IfStatement const& _node)
{
    addSourceFromDocStrings(_node.annotation());

    add("if ");
    _node.condition().accept(*this);
    add(" then");
    visitIndentedUnlessBlock(_node.trueStatement());
    if (_node.falseStatement())
    {
        newLine();
        add("else");
        visitIndentedUnlessBlock(*_node.falseStatement());
    }
    return false;
}

bool Why3Translator::visit(WhileStatement const& _node)
{
    addSourceFromDocStrings(_node.annotation());

    add("while ");
    _node.condition().accept(*this);
    newLine();
    add("do");
    visitIndentedUnlessBlock(_node.body());
    add("done");
    return false;
}

bool Why3Translator::visit(Return const& _node)
{
    addSourceFromDocStrings(_node.annotation());

    if (_node.expression())
    {
        solAssert(!!_node.annotation().functionReturnParameters, "");
        auto const& params = _node.annotation().functionReturnParameters->parameters();
        if (params.size() != 1)
        {
            error(_node, "Directly returning tuples not supported. Rather assign to return variable.");
            return false;
        }
        add("begin _" + params.front()->name() + " := ");
        _node.expression()->accept(*this);
        add("; raise Ret end");
    }
    else
        add("raise Ret");
    return false;
}

bool Why3Translator::visit(VariableDeclarationStatement const& _node)
{
    addSourceFromDocStrings(_node.annotation());

    if (_node.declarations().size() != 1)
    {
        error(_node, "Multiple variables not supported.");
        return false;
    }
    if (_node.initialValue())
    {
        add("_" + _node.declarations().front()->name() + " := ");
        _node.initialValue()->accept(*this);
    }
    return false;
}

bool Why3Translator::visit(ExpressionStatement const& _node)
{
    addSourceFromDocStrings(_node.annotation());
    return true;
}

bool Why3Translator::visit(Assignment const& _node)
{
    if (_node.assignmentOperator() != Token::Assign)
        error(_node, "Compound assignment not supported.");

    _node.leftHandSide().accept(*this);
    add(" := ");
    _node.rightHandSide().accept(*this);

    return false;
}

bool Why3Translator::visit(TupleExpression const& _node)
{
    if (_node.components().size() != 1)
        error(_node, "Only tuples with exactly one component supported.");
    add("(");
    return true;
}

bool Why3Translator::visit(UnaryOperation const& _unaryOperation)
{
    if (toFormalType(*_unaryOperation.annotation().type).empty())
        error(_unaryOperation, "Type not supported.");

    switch (_unaryOperation.getOperator())
    {
    case Token::Not: // !
        add("(not ");
        break;
    default:
        error(_unaryOperation, "Operator not supported.");
        break;
    }

    _unaryOperation.subExpression().accept(*this);
    add(")");

    return false;
}

bool Why3Translator::visit(BinaryOperation const& _binaryOperation)
{
    Expression const& leftExpression = _binaryOperation.leftExpression();
    Expression const& rightExpression = _binaryOperation.rightExpression();
    solAssert(!!_binaryOperation.annotation().commonType, "");
    Type const& commonType = *_binaryOperation.annotation().commonType;
    Token::Value const c_op = _binaryOperation.getOperator();

    if (commonType.category() == Type::Category::IntegerConstant)
    {
        add("(of_int " + toString(commonType.literalValue(nullptr)) + ")");
        return false;
    }
    static const map<Token::Value, char const*> optrans({
        {Token::And, " && "},
        {Token::Or, " || "},
        {Token::BitOr, " lor "},
        {Token::BitXor, " lxor "},
        {Token::BitAnd, " land "},
        {Token::Add, " + "},
        {Token::Sub, " - "},
        {Token::Mul, " * "},
        {Token::Div, " / "},
        {Token::Mod, " mod "},
        {Token::Equal, " = "},
        {Token::NotEqual, " <> "},
        {Token::LessThan, " < "},
        {Token::GreaterThan, " > "},
        {Token::LessThanOrEqual, " <= "},
        {Token::GreaterThanOrEqual, " >= "}
    });
    if (!optrans.count(c_op))
        error(_binaryOperation, "Operator not supported.");

    add("(");
    leftExpression.accept(*this);
    add(optrans.at(c_op));
    rightExpression.accept(*this);
    add(")");

    return false;
}

bool Why3Translator::visit(FunctionCall const& _node)
{
    if (_node.annotation().isTypeConversion || _node.annotation().isStructConstructorCall)
    {
        error(_node, "Only ordinary function calls supported.");
        return true;
    }
    FunctionType const& function = dynamic_cast<FunctionType const&>(*_node.expression().annotation().type);
    if (function.location() != FunctionType::Location::Internal)
    {
        error(_node, "Only internal function calls supported.");
        return true;
    }
    if (!_node.names().empty())
    {
        error(_node, "Function calls with named arguments not supported.");
        return true;
    }

    //@TODO check type conversions

    add("(");
    _node.expression().accept(*this);
    add(" state");
    for (auto const& arg: _node.arguments())
    {
        add(" ");
        arg->accept(*this);
    }
    add(")");
    return false;
}

bool Why3Translator::visit(MemberAccess const& _node)
{
    if (
        _node.expression().annotation().type->category() == Type::Category::Array &&
        _node.memberName() == "length" &&
        !_node.annotation().lValueRequested
    )
    {
        add("(of_int ");
        _node.expression().accept(*this);
        add(".length");
        add(")");
    }
    else
        error(_node, "Only read-only length access for arrays supported.");
    return false;
}

bool Why3Translator::visit(IndexAccess const& _node)
{
    auto baseType = dynamic_cast<ArrayType const*>(_node.baseExpression().annotation().type.get());
    if (!baseType)
    {
        error(_node, "Index access only supported for arrays.");
        return true;
    }
    if (_node.annotation().lValueRequested)
    {
        error(_node, "Assignment to array elements not supported.");
        return true;
    }
    add("(");
    _node.baseExpression().accept(*this);
    add("[to_int ");
    _node.indexExpression()->accept(*this);
    add("]");
    add(")");

    return false;
}

bool Why3Translator::visit(Identifier const& _identifier)
{
    Declaration const* declaration = _identifier.annotation().referencedDeclaration;
    if (FunctionDefinition const* functionDef = dynamic_cast<FunctionDefinition const*>(declaration))
        add("_" + functionDef->name());
    else if (auto variable = dynamic_cast<VariableDeclaration const*>(declaration))
    {
        bool isStateVar = isStateVariable(variable);
        bool lvalue = _identifier.annotation().lValueRequested;
        if (!lvalue)
            add("!(");
        if (isStateVar)
            add("state.");
        add("_" + variable->name());
        if (!lvalue)
            add(")");
    }
    else
        error(_identifier, "Not supported.");
    return false;
}

bool Why3Translator::visit(Literal const& _literal)
{
    TypePointer type = _literal.annotation().type;
    switch (type->category())
    {
    case Type::Category::Bool:
        if (type->literalValue(&_literal) == 0)
            add("false");
        else
            add("true");
        break;
    case Type::Category::IntegerConstant:
        add("(of_int " + toString(type->literalValue(&_literal)) + ")");
        break;
    default:
        error(_literal, "Not supported.");
    }
    return false;
}

bool Why3Translator::isStateVariable(VariableDeclaration const* _var) const
{
    solAssert(!!m_stateVariables, "");
    for (auto const& var: *m_stateVariables)
        if (var.get() == _var)
            return true;
    return false;
}

void Why3Translator::visitIndentedUnlessBlock(Statement const& _statement)
{
    bool isBlock = !!dynamic_cast<Block const*>(&_statement);
    if (isBlock)
        newLine();
    else
        indent();
    _statement.accept(*this);
    if (isBlock)
        newLine();
    else
        unindent();
}

void Why3Translator::addSourceFromDocStrings(DocumentedAnnotation const& _annotation)
{
    auto why3Range = _annotation.docTags.equal_range("why3");
    for (auto i = why3Range.first; i != why3Range.second; ++i)
        addLine(i->second.content);
}