path: root/AST.h

/*
    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.
 */

#pragma once


#include <string>
#include <vector>
#include <memory>
#include <boost/noncopyable.hpp>
#include <libevmasm/SourceLocation.h>
#include <libsolidity/Utils.h>
#include <libsolidity/ASTForward.h>
#include <libsolidity/Token.h>
#include <libsolidity/Types.h>
#include <libsolidity/Exceptions.h>

namespace dev
{
namespace solidity
{

class ASTVisitor;
class ASTConstVisitor;


/**
 * The root (abstract) class of the AST inheritance tree.
 * It is possible to traverse all direct and indirect children of an AST node by calling
 * accept, providing an ASTVisitor.
 */
class ASTNode: private boost::noncopyable
{
public:
    explicit ASTNode(SourceLocation const& _location): m_location(_location) {}

    virtual ~ASTNode() {}

    virtual void accept(ASTVisitor& _visitor) = 0;
    virtual void accept(ASTConstVisitor& _visitor) const = 0;
    template <class T>
    static void listAccept(std::vector<ASTPointer<T>>& _list, ASTVisitor& _visitor)
    {
        for (ASTPointer<T>& element: _list)
            element->accept(_visitor);
    }
    template <class T>
    static void listAccept(std::vector<ASTPointer<T>> const& _list, ASTConstVisitor& _visitor)
    {
        for (ASTPointer<T> const& element: _list)
            element->accept(_visitor);
    }

    /// Returns the source code location of this node.
    SourceLocation const& getLocation() const { return m_location; }

    /// Creates a @ref TypeError exception and decorates it with the location of the node and
    /// the given description
    TypeError createTypeError(std::string const& _description) const;

    ///@{
    ///@name equality operators
    /// Equality relies on the fact that nodes cannot be copied.
    bool operator==(ASTNode const& _other) const { return this == &_other; }
    bool operator!=(ASTNode const& _other) const { return !operator==(_other); }
    ///@}

private:
    SourceLocation m_location;
};

/**
 * Source unit containing import directives and contract definitions.
 */
class SourceUnit: public ASTNode
{
public:
    SourceUnit(SourceLocation const& _location, std::vector<ASTPointer<ASTNode>> const& _nodes):
        ASTNode(_location), m_nodes(_nodes) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    std::vector<ASTPointer<ASTNode>> getNodes() const { return m_nodes; }

private:
    std::vector<ASTPointer<ASTNode>> m_nodes;
};

/**
 * Import directive for referencing other files / source objects.
 * Example: import "abc.sol"
 * Source objects are identified by a string which can be a file name but does not have to be.
 */
class ImportDirective: public ASTNode
{
public:
    ImportDirective(SourceLocation const& _location, ASTPointer<ASTString> const& _identifier):
        ASTNode(_location), m_identifier(_identifier) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    ASTString const& getIdentifier() const { return *m_identifier; }

private:
    ASTPointer<ASTString> m_identifier;
};

/**
 * Abstract AST class for a declaration (contract, function, struct, variable).
 */
class Declaration: public ASTNode
{
public:
    /// Visibility ordered from restricted to unrestricted.
    enum class Visibility { Default, Private, Internal, Public, External };

    Declaration(SourceLocation const& _location, ASTPointer<ASTString> const& _name,
                Visibility _visibility = Visibility::Default):
        ASTNode(_location), m_name(_name), m_visibility(_visibility), m_scope(nullptr) {}

    /// @returns the declared name.
    ASTString const& getName() const { return *m_name; }
    Visibility getVisibility() const { return m_visibility == Visibility::Default ? getDefaultVisibility() : m_visibility; }
    bool isPublic() const { return getVisibility() >= Visibility::Public; }
    virtual bool isVisibleInContract() const { return getVisibility() != Visibility::External; }
    bool isVisibleInDerivedContracts() const { return isVisibleInContract() && getVisibility() >= Visibility::Internal; }

    /// @returns the scope this declaration resides in. Can be nullptr if it is the global scope.
    /// Available only after name and type resolution step.
    Declaration const* getScope() const { return m_scope; }
    void setScope(Declaration const* _scope) { m_scope = _scope; }

    /// @returns the type of expressions referencing this declaration.
    /// The current contract has to be given since this context can change the type, especially of
    /// contract types.
    virtual TypePointer getType(ContractDefinition const* m_currentContract = nullptr) const = 0;
    virtual bool isLValue() const { return false; }
    virtual bool isPartOfExternalInterface() const { return false; }

protected:
    virtual Visibility getDefaultVisibility() const { return Visibility::Public; }

private:
    ASTPointer<ASTString> m_name;
    Visibility m_visibility;
    Declaration const* m_scope;
};

/**
 * Abstract class that is added to each AST node that can store local variables.
 */
class VariableScope
{
public:
    void addLocalVariable(VariableDeclaration const& _localVariable) { m_localVariables.push_back(&_localVariable); }
    std::vector<VariableDeclaration const*> const& getLocalVariables() const { return m_localVariables; }

private:
    std::vector<VariableDeclaration const*> m_localVariables;
};

/**
 * Abstract class that is added to each AST node that can receive documentation.
 */
class Documented
{
public:
    explicit Documented(ASTPointer<ASTString> const& _documentation): m_documentation(_documentation) {}

    /// @return A shared pointer of an ASTString.
    /// Can contain a nullptr in which case indicates absence of documentation
    ASTPointer<ASTString> const& getDocumentation() const { return m_documentation; }

protected:
    ASTPointer<ASTString> m_documentation;
};

/**
 * Abstract class that is added to AST nodes that can be marked as not being fully implemented
 */
class ImplementationOptional
{
public:
    explicit ImplementationOptional(bool _implemented): m_implemented(_implemented) {}

    /// @return whether this node is fully implemented or not
    bool isFullyImplemented() const { return m_implemented; }
    void setFullyImplemented(bool _implemented) {  m_implemented = _implemented; }

protected:
    bool m_implemented;
};

/// @}

/**
 * Definition of a contract. This is the only AST nodes where child nodes are not visited in
 * document order. It first visits all struct declarations, then all variable declarations and
 * finally all function declarations.
 */
class ContractDefinition: public Declaration, public Documented, public ImplementationOptional
{
public:
    ContractDefinition(
        SourceLocation const& _location,
        ASTPointer<ASTString> const& _name,
        ASTPointer<ASTString> const& _documentation,
        std::vector<ASTPointer<InheritanceSpecifier>> const& _baseContracts,
        std::vector<ASTPointer<StructDefinition>> const& _definedStructs,
        std::vector<ASTPointer<EnumDefinition>> const& _definedEnums,
        std::vector<ASTPointer<VariableDeclaration>> const& _stateVariables,
        std::vector<ASTPointer<FunctionDefinition>> const& _definedFunctions,
        std::vector<ASTPointer<ModifierDefinition>> const& _functionModifiers,
        std::vector<ASTPointer<EventDefinition>> const& _events
    ):
        Declaration(_location, _name),
        Documented(_documentation),
        ImplementationOptional(true),
        m_baseContracts(_baseContracts),
        m_definedStructs(_definedStructs),
        m_definedEnums(_definedEnums),
        m_stateVariables(_stateVariables),
        m_definedFunctions(_definedFunctions),
        m_functionModifiers(_functionModifiers),
        m_events(_events)
    {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    std::vector<ASTPointer<InheritanceSpecifier>> const& getBaseContracts() const { return m_baseContracts; }
    std::vector<ASTPointer<StructDefinition>> const& getDefinedStructs() const { return m_definedStructs; }
    std::vector<ASTPointer<EnumDefinition>> const& getDefinedEnums() const { return m_definedEnums; }
    std::vector<ASTPointer<VariableDeclaration>> const& getStateVariables() const { return m_stateVariables; }
    std::vector<ASTPointer<ModifierDefinition>> const& getFunctionModifiers() const { return m_functionModifiers; }
    std::vector<ASTPointer<FunctionDefinition>> const& getDefinedFunctions() const { return m_definedFunctions; }
    std::vector<ASTPointer<EventDefinition>> const& getEvents() const { return m_events; }
    std::vector<ASTPointer<EventDefinition>> const& getInterfaceEvents() const;

    virtual TypePointer getType(ContractDefinition const* m_currentContract) const override;

    /// Checks that there are no illegal overrides, that the constructor does not have a "returns"
    /// and calls checkTypeRequirements on all its functions.
    void checkTypeRequirements();

    /// @returns a map of canonical function signatures to FunctionDefinitions
    /// as intended for use by the ABI.
    std::map<FixedHash<4>, FunctionTypePointer> getInterfaceFunctions() const;

    /// @returns a list of the inheritable members of this contract
    std::vector<Declaration const*> const& getInheritableMembers() const;

    /// List of all (direct and indirect) base contracts in order from derived to base, including
    /// the contract itself. Available after name resolution
    std::vector<ContractDefinition const*> const& getLinearizedBaseContracts() const { return m_linearizedBaseContracts; }
    void setLinearizedBaseContracts(std::vector<ContractDefinition const*> const& _bases) { m_linearizedBaseContracts = _bases; }

    /// Returns the constructor or nullptr if no constructor was specified.
    FunctionDefinition const* getConstructor() const;
    /// Returns the fallback function or nullptr if no fallback function was specified.
    FunctionDefinition const* getFallbackFunction() const;

private:
    /// Checks that two functions defined in this contract with the same name have different
    /// arguments and that there is at most one constructor.
    void checkDuplicateFunctions() const;
    void checkIllegalOverrides() const;
    void checkAbstractFunctions();
    void checkAbstractConstructors();
    /// Checks that different functions with external visibility end up having different
    /// external argument types (i.e. different signature).
    void checkExternalTypeClashes() const;

    std::vector<std::pair<FixedHash<4>, FunctionTypePointer>> const& getInterfaceFunctionList() const;

    std::vector<ASTPointer<InheritanceSpecifier>> m_baseContracts;
    std::vector<ASTPointer<StructDefinition>> m_definedStructs;
    std::vector<ASTPointer<EnumDefinition>> m_definedEnums;
    std::vector<ASTPointer<VariableDeclaration>> m_stateVariables;
    std::vector<ASTPointer<FunctionDefinition>> m_definedFunctions;
    std::vector<ASTPointer<ModifierDefinition>> m_functionModifiers;
    std::vector<ASTPointer<EventDefinition>> m_events;

    std::vector<ContractDefinition const*> m_linearizedBaseContracts;
    mutable std::unique_ptr<std::vector<std::pair<FixedHash<4>, FunctionTypePointer>>> m_interfaceFunctionList;
    mutable std::unique_ptr<std::vector<ASTPointer<EventDefinition>>> m_interfaceEvents;
    mutable std::unique_ptr<std::vector<Declaration const*>> m_inheritableMembers;
};

class InheritanceSpecifier: public ASTNode
{
public:
    InheritanceSpecifier(SourceLocation const& _location, ASTPointer<Identifier> const& _baseName,
                         std::vector<ASTPointer<Expression>> _arguments):
        ASTNode(_location), m_baseName(_baseName), m_arguments(_arguments) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    ASTPointer<Identifier> const& getName() const { return m_baseName; }
    std::vector<ASTPointer<Expression>> const& getArguments() const { return m_arguments; }

    void checkTypeRequirements();

private:
    ASTPointer<Identifier> m_baseName;
    std::vector<ASTPointer<Expression>> m_arguments;
};

class StructDefinition: public Declaration
{
public:
    StructDefinition(SourceLocation const& _location,
                     ASTPointer<ASTString> const& _name,
                     std::vector<ASTPointer<VariableDeclaration>> const& _members):
        Declaration(_location, _name), m_members(_members) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    std::vector<ASTPointer<VariableDeclaration>> const& getMembers() const { return m_members; }

    virtual TypePointer getType(ContractDefinition const*) const override;

    /// Checks that the members do not include any recursive structs and have valid types
    /// (e.g. no functions).
    void checkValidityOfMembers() const;

private:
    void checkMemberTypes() const;
    void checkRecursion() const;

    std::vector<ASTPointer<VariableDeclaration>> m_members;
};

class EnumDefinition: public Declaration
{
public:
    EnumDefinition(SourceLocation const& _location,
                   ASTPointer<ASTString> const& _name,
                   std::vector<ASTPointer<EnumValue>> const& _members):
        Declaration(_location, _name), m_members(_members) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    std::vector<ASTPointer<EnumValue>> const& getMembers() const { return m_members; }

    virtual TypePointer getType(ContractDefinition const*) const override;

private:
    std::vector<ASTPointer<EnumValue>> m_members;
};

/**
 * Declaration of an Enum Value
 */
class EnumValue: public Declaration
{
  public:
    EnumValue(SourceLocation const& _location,
              ASTPointer<ASTString> const& _name):
        Declaration(_location, _name) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual TypePointer getType(ContractDefinition const* = nullptr) const override;
};

/**
 * Parameter list, used as function parameter list and return list.
 * None of the parameters is allowed to contain mappings (not even recursively
 * inside structs).
 */
class ParameterList: public ASTNode
{
public:
    ParameterList(SourceLocation const& _location,
                  std::vector<ASTPointer<VariableDeclaration>> const& _parameters):
        ASTNode(_location), m_parameters(_parameters) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    std::vector<ASTPointer<VariableDeclaration>> const& getParameters() const { return m_parameters; }

private:
    std::vector<ASTPointer<VariableDeclaration>> m_parameters;
};

/**
 * Base class for all nodes that define function-like objects, i.e. FunctionDefinition,
 * EventDefinition and ModifierDefinition.
 */
class CallableDeclaration: public Declaration, public VariableScope
{
public:
    CallableDeclaration(
        SourceLocation const& _location,
        ASTPointer<ASTString> const& _name,
        Declaration::Visibility _visibility,
        ASTPointer<ParameterList> const& _parameters,
        ASTPointer<ParameterList> const& _returnParameters = ASTPointer<ParameterList>()
    ):
        Declaration(_location, _name, _visibility),
        m_parameters(_parameters),
        m_returnParameters(_returnParameters)
    {
    }

    std::vector<ASTPointer<VariableDeclaration>> const& getParameters() const { return m_parameters->getParameters(); }
    ParameterList const& getParameterList() const { return *m_parameters; }
    ASTPointer<ParameterList> const& getReturnParameterList() const { return m_returnParameters; }

protected:
    ASTPointer<ParameterList> m_parameters;
    ASTPointer<ParameterList> m_returnParameters;
};

class FunctionDefinition: public CallableDeclaration, public Documented, public ImplementationOptional
{
public:
    FunctionDefinition(
        SourceLocation const& _location,
        ASTPointer<ASTString> const& _name,
        Declaration::Visibility _visibility,
        bool _isConstructor,
        ASTPointer<ASTString> const& _documentation,
        ASTPointer<ParameterList> const& _parameters,
        bool _isDeclaredConst,
        std::vector<ASTPointer<ModifierInvocation>> const& _modifiers,
        ASTPointer<ParameterList> const& _returnParameters,
        ASTPointer<Block> const& _body
    ):
        CallableDeclaration(_location, _name, _visibility, _parameters, _returnParameters),
        Documented(_documentation),
        ImplementationOptional(_body != nullptr),
        m_isConstructor(_isConstructor),
        m_isDeclaredConst(_isDeclaredConst),
        m_functionModifiers(_modifiers),
        m_body(_body)
    {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    bool isConstructor() const { return m_isConstructor; }
    bool isDeclaredConst() const { return m_isDeclaredConst; }
    std::vector<ASTPointer<ModifierInvocation>> const& getModifiers() const { return m_functionModifiers; }
    std::vector<ASTPointer<VariableDeclaration>> const& getReturnParameters() const { return m_returnParameters->getParameters(); }
    Block const& getBody() const { return *m_body; }

    virtual bool isVisibleInContract() const override
    {
        return Declaration::isVisibleInContract() && !isConstructor() && !getName().empty();
    }
    virtual TypePointer getType(ContractDefinition const*) const override;
    virtual bool isPartOfExternalInterface() const override { return isPublic() && !m_isConstructor && !getName().empty(); }

    /// Checks that all parameters have allowed types and calls checkTypeRequirements on the body.
    void checkTypeRequirements();

    /// @returns the external signature of the function
    /// That consists of the name of the function followed by the types of the
    /// arguments separated by commas all enclosed in parentheses without any spaces.
    std::string externalSignature() const;

private:
    bool m_isConstructor;
    bool m_isDeclaredConst;
    std::vector<ASTPointer<ModifierInvocation>> m_functionModifiers;
    ASTPointer<Block> m_body;
};

/**
 * Declaration of a variable. This can be used in various places, e.g. in function parameter
 * lists, struct definitions and even function bodys.
 */
class VariableDeclaration: public Declaration
{
public:
    enum Location { Default, Storage, Memory };

    VariableDeclaration(
        SourceLocation const& _sourceLocation,
        ASTPointer<TypeName> const& _type,
        ASTPointer<ASTString> const& _name,
        ASTPointer<Expression> _value,
        Visibility _visibility,
        bool _isStateVar = false,
        bool _isIndexed = false,
        bool _isConstant = false,
        Location _referenceLocation = Location::Default
    ):
        Declaration(_sourceLocation, _name, _visibility),
        m_typeName(_type),
        m_value(_value),
        m_isStateVariable(_isStateVar),
        m_isIndexed(_isIndexed),
        m_isConstant(_isConstant),
        m_location(_referenceLocation) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    TypeName* getTypeName() { return m_typeName.get(); }
    ASTPointer<Expression> const& getValue() const { return m_value; }

    /// Returns the declared or inferred type. Can be an empty pointer if no type was explicitly
    /// declared and there is no assignment to the variable that fixes the type.
    TypePointer getType(ContractDefinition const* = nullptr) const override { return m_type; }
    void setType(std::shared_ptr<Type const> const& _type) { m_type = _type; }

    virtual bool isLValue() const override;
    virtual bool isPartOfExternalInterface() const override { return isPublic() && !m_isConstant; }

    void checkTypeRequirements();
    bool isLocalVariable() const { return !!dynamic_cast<FunctionDefinition const*>(getScope()); }
    /// @returns true if this variable is a parameter or return parameter of a function.
    bool isCallableParameter() const;
    /// @returns true if this variable is a parameter (not return parameter) of an external function.
    bool isExternalCallableParameter() const;
    bool isStateVariable() const { return m_isStateVariable; }
    bool isIndexed() const { return m_isIndexed; }
    bool isConstant() const { return m_isConstant; }
    Location referenceLocation() const { return m_location; }

protected:
    Visibility getDefaultVisibility() const override { return Visibility::Internal; }

private:
    ASTPointer<TypeName> m_typeName; ///< can be empty ("var")
    ASTPointer<Expression> m_value; ///< the assigned value, can be missing
    bool m_isStateVariable; ///< Whether or not this is a contract state variable
    bool m_isIndexed; ///< Whether this is an indexed variable (used by events).
    bool m_isConstant; ///< Whether the variable is a compile-time constant.
    Location m_location; ///< Location of the variable if it is of reference type.

    std::shared_ptr<Type const> m_type; ///< derived type, initially empty
};

/**
 * Definition of a function modifier.
 */
class ModifierDefinition: public CallableDeclaration, public Documented
{
public:
    ModifierDefinition(
        SourceLocation const& _location,
        ASTPointer<ASTString> const& _name,
        ASTPointer<ASTString> const& _documentation,
        ASTPointer<ParameterList> const& _parameters,
        ASTPointer<Block> const& _body
    ):
        CallableDeclaration(_location, _name, Visibility::Default, _parameters),
        Documented(_documentation),
        m_body(_body)
    {
    }

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    Block const& getBody() const { return *m_body; }

    virtual TypePointer getType(ContractDefinition const* = nullptr) const override;

    void checkTypeRequirements();

private:
    ASTPointer<Block> m_body;
};

/**
 * Invocation/usage of a modifier in a function header or a base constructor call.
 */
class ModifierInvocation: public ASTNode
{
public:
    ModifierInvocation(SourceLocation const& _location, ASTPointer<Identifier> const& _name,
                       std::vector<ASTPointer<Expression>> _arguments):
        ASTNode(_location), m_modifierName(_name), m_arguments(_arguments) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    ASTPointer<Identifier> const& getName() const { return m_modifierName; }
    std::vector<ASTPointer<Expression>> const& getArguments() const { return m_arguments; }

    /// @param _bases is the list of base contracts for base constructor calls. For modifiers an empty vector should be passed.
    void checkTypeRequirements(std::vector<ContractDefinition const*> const& _bases);

private:
    ASTPointer<Identifier> m_modifierName;
    std::vector<ASTPointer<Expression>> m_arguments;
};

/**
 * Definition of a (loggable) event.
 */
class EventDefinition: public CallableDeclaration, public Documented
{
public:
    EventDefinition(
        SourceLocation const& _location,
        ASTPointer<ASTString> const& _name,
        ASTPointer<ASTString> const& _documentation,
        ASTPointer<ParameterList> const& _parameters,
        bool _anonymous = false
    ):
        CallableDeclaration(_location, _name, Visibility::Default, _parameters),
        Documented(_documentation),
        m_anonymous(_anonymous)
    {
    }

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    bool isAnonymous() const { return m_anonymous; }

    virtual TypePointer getType(ContractDefinition const* = nullptr) const override
    {
        return std::make_shared<FunctionType>(*this);
    }

    void checkTypeRequirements();

private:
    bool m_anonymous = false;
};

/**
 * Pseudo AST node that is used as declaration for "this", "msg", "tx", "block" and the global
 * functions when such an identifier is encountered. Will never have a valid location in the source code.
 */
class MagicVariableDeclaration: public Declaration
{
public:
    MagicVariableDeclaration(ASTString const& _name, std::shared_ptr<Type const> const& _type):
        Declaration(SourceLocation(), std::make_shared<ASTString>(_name)), m_type(_type) {}
    virtual void accept(ASTVisitor&) override { BOOST_THROW_EXCEPTION(InternalCompilerError()
                            << errinfo_comment("MagicVariableDeclaration used inside real AST.")); }
    virtual void accept(ASTConstVisitor&) const override { BOOST_THROW_EXCEPTION(InternalCompilerError()
                            << errinfo_comment("MagicVariableDeclaration used inside real AST.")); }

    virtual TypePointer getType(ContractDefinition const* = nullptr) const override { return m_type; }

private:
    std::shared_ptr<Type const> m_type;
};

/// Types
/// @{

/**
 * Abstract base class of a type name, can be any built-in or user-defined type.
 */
class TypeName: public ASTNode
{
public:
    explicit TypeName(SourceLocation const& _location): ASTNode(_location) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    /// Retrieve the element of the type hierarchy this node refers to. Can return an empty shared
    /// pointer until the types have been resolved using the @ref NameAndTypeResolver.
    /// If it returns an empty shared pointer after that, this indicates that the type was not found.
    virtual std::shared_ptr<Type const> toType() = 0;
};

/**
 * Any pre-defined type name represented by a single keyword, i.e. it excludes mappings,
 * contracts, functions, etc.
 */
class ElementaryTypeName: public TypeName
{
public:
    explicit ElementaryTypeName(SourceLocation const& _location, Token::Value _type):
        TypeName(_location), m_type(_type)
    {
        solAssert(Token::isElementaryTypeName(_type), "");
    }
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual std::shared_ptr<Type const> toType() override { return Type::fromElementaryTypeName(m_type); }

    Token::Value getTypeName() const { return m_type; }

private:
    Token::Value m_type;
};

/**
 * Name referring to a user-defined type (i.e. a struct, contract, etc.).
 */
class UserDefinedTypeName: public TypeName
{
public:
    UserDefinedTypeName(SourceLocation const& _location, ASTPointer<ASTString> const& _name):
        TypeName(_location), m_name(_name), m_referencedDeclaration(nullptr) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual std::shared_ptr<Type const> toType() override { return Type::fromUserDefinedTypeName(*this); }

    ASTString const& getName() const { return *m_name; }
    void setReferencedDeclaration(Declaration const& _referencedDeclaration) { m_referencedDeclaration = &_referencedDeclaration; }
    Declaration const* getReferencedDeclaration() const { return m_referencedDeclaration; }

private:
    ASTPointer<ASTString> m_name;

    Declaration const* m_referencedDeclaration;
};

/**
 * A mapping type. Its source form is "mapping('keyType' => 'valueType')"
 */
class Mapping: public TypeName
{
public:
    Mapping(SourceLocation const& _location, ASTPointer<ElementaryTypeName> const& _keyType,
            ASTPointer<TypeName> const& _valueType):
        TypeName(_location), m_keyType(_keyType), m_valueType(_valueType) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual TypePointer toType() override { return Type::fromMapping(*m_keyType, *m_valueType); }

    ElementaryTypeName const& getKeyType() const { return *m_keyType; }
    TypeName const& getValueType() const { return *m_valueType; }

private:
    ASTPointer<ElementaryTypeName> m_keyType;
    ASTPointer<TypeName> m_valueType;
};

/**
 * An array type, can be "typename[]" or "typename[<expression>]".
 */
class ArrayTypeName: public TypeName
{
public:
    ArrayTypeName(SourceLocation const& _location, ASTPointer<TypeName> const& _baseType,
            ASTPointer<Expression> const& _length):
        TypeName(_location), m_baseType(_baseType), m_length(_length) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual std::shared_ptr<Type const> toType() override { return Type::fromArrayTypeName(*m_baseType, m_length.get()); }

    TypeName const& getBaseType() const { return *m_baseType; }
    Expression const* getLength() const { return m_length.get(); }

private:
    ASTPointer<TypeName> m_baseType;
    ASTPointer<Expression> m_length; ///< Length of the array, might be empty.
};

/// @}

/// Statements
/// @{


/**
 * Abstract base class for statements.
 */
class Statement: public ASTNode
{
public:
    explicit Statement(SourceLocation const& _location): ASTNode(_location) {}

    /// Check all type requirements, throws exception if some requirement is not met.
    /// This includes checking that operators are applicable to their arguments but also that
    /// the number of function call arguments matches the number of formal parameters and so forth.
    virtual void checkTypeRequirements() = 0;
};

/**
 * Brace-enclosed block containing zero or more statements.
 */
class Block: public Statement
{
public:
    Block(SourceLocation const& _location, std::vector<ASTPointer<Statement>> const& _statements):
        Statement(_location), m_statements(_statements) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    virtual void checkTypeRequirements() override;

private:
    std::vector<ASTPointer<Statement>> m_statements;
};

/**
 * Special placeholder statement denoted by "_" used in function modifiers. This is replaced by
 * the original function when the modifier is applied.
 */
class PlaceholderStatement: public Statement
{
public:
    PlaceholderStatement(SourceLocation const& _location): Statement(_location) {}

    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;

    virtual void checkTypeRequirements() override { }
};

/**
 * If-statement with an optional "else" part. Note that "else if" is modeled by having a new
 * if-statement as the false (else) body.
 */
class IfStatement: public Statement
{
public:
    IfStatement(SourceLocation const& _location, ASTPointer<Expression> const& _condition,
                ASTPointer<Statement> const& _trueBody, ASTPointer<Statement> const& _falseBody):
        Statement(_location),
        m_condition(_condition), m_trueBody(_trueBody), m_falseBody(_falseBody) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    Expression const& getCondition() const { return *m_condition; }
    Statement const& getTrueStatement() const { return *m_trueBody; }
    /// @returns the "else" part of the if statement or nullptr if there is no "else" part.
    Statement const* getFalseStatement() const { return m_falseBody.get(); }

private:
    ASTPointer<Expression> m_condition;
    ASTPointer<Statement> m_trueBody;
    ASTPointer<Statement> m_falseBody; ///< "else" part, optional
};

/**
 * Statement in which a break statement is legal (abstract class).
 */
class BreakableStatement: public Statement
{
public:
    BreakableStatement(SourceLocation const& _location): Statement(_location) {}
};

class WhileStatement: public BreakableStatement
{
public:
    WhileStatement(SourceLocation const& _location, ASTPointer<Expression> const& _condition,
                   ASTPointer<Statement> const& _body):
        BreakableStatement(_location), m_condition(_condition), m_body(_body) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    Expression const& getCondition() const { return *m_condition; }
    Statement const& getBody() const { return *m_body; }

private:
    ASTPointer<Expression> m_condition;
    ASTPointer<Statement> m_body;
};

/**
 * For loop statement
 */
class ForStatement: public BreakableStatement
{
public:
    ForStatement(SourceLocation const& _location,
                 ASTPointer<Statement> const& _initExpression,
                 ASTPointer<Expression> const& _conditionExpression,
                 ASTPointer<ExpressionStatement> const& _loopExpression,
                 ASTPointer<Statement> const& _body):
        BreakableStatement(_location),
        m_initExpression(_initExpression),
        m_condExpression(_conditionExpression),
        m_loopExpression(_loopExpression),
        m_body(_body) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    Statement const* getInitializationExpression() const { return m_initExpression.get(); }
    Expression const* getCondition() const { return m_condExpression.get(); }
    ExpressionStatement const* getLoopExpression() const { return m_loopExpression.get(); }
    Statement const& getBody() const { return *m_body; }

private:
    /// For statement's initialization expresion. for(XXX; ; ). Can be empty
    ASTPointer<Statement> m_initExpression;
    /// For statement's condition expresion. for(; XXX ; ). Can be empty
    ASTPointer<Expression> m_condExpression;
    /// For statement's loop expresion. for(;;XXX). Can be empty
    ASTPointer<ExpressionStatement> m_loopExpression;
    /// The body of the loop
    ASTPointer<Statement> m_body;
};

class Continue: public Statement
{
public:
    Continue(SourceLocation const& _location): Statement(_location) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override {}
};

class Break: public Statement
{
public:
    Break(SourceLocation const& _location): Statement(_location) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override {}
};

class Return: public Statement
{
public:
    Return(SourceLocation const& _location, ASTPointer<Expression> _expression):
        Statement(_location), m_expression(_expression), m_returnParameters(nullptr) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    void setFunctionReturnParameters(ParameterList const* _parameters) { m_returnParameters = _parameters; }
    ParameterList const* getFunctionReturnParameters() const { return m_returnParameters; }
    Expression const* getExpression() const { return m_expression.get(); }

private:
    ASTPointer<Expression> m_expression; ///< value to return, optional

    /// Pointer to the parameter list of the function, filled by the @ref NameAndTypeResolver.
    ParameterList const* m_returnParameters;
};

/**
 * Definition of a variable as a statement inside a function. It requires a type name (which can
 * also be "var") but the actual assignment can be missing.
 * Examples: var a = 2; uint256 a;
 */
class VariableDeclarationStatement: public Statement
{
public:
    VariableDeclarationStatement(SourceLocation const& _location, ASTPointer<VariableDeclaration> _variable):
        Statement(_location), m_variable(_variable) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    VariableDeclaration const& getDeclaration() const { return *m_variable; }
    Expression const* getExpression() const { return m_variable->getValue().get(); }

private:
    ASTPointer<VariableDeclaration> m_variable;
};

/**
 * A statement that contains only an expression (i.e. an assignment, function call, ...).
 */
class ExpressionStatement: public Statement
{
public:
    ExpressionStatement(SourceLocation const& _location, ASTPointer<Expression> _expression):
        Statement(_location), m_expression(_expression) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements() override;

    Expression const& getExpression() const { return *m_expression; }

private:
    ASTPointer<Expression> m_expression;
};

/// @}

/// Expressions
/// @{

/**
 * An expression, i.e. something that has a value (which can also be of type "void" in case
 * of some function calls).
 * @abstract
 */
class Expression: public ASTNode
{
public:
    Expression(SourceLocation const& _location): ASTNode(_location) {}
    /// Performs type checking after which m_type should be set.
    /// @arg _argumentTypes if set, provides the argument types for the case that this expression
    /// is used in the context of a call, used for function overload resolution.
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) = 0;

    std::shared_ptr<Type const> const& getType() const { return m_type; }
    bool isLValue() const { return m_isLValue; }

    /// Helper function, infer the type via @ref checkTypeRequirements and then check that it
    /// is implicitly convertible to @a _expectedType. If not, throw exception.
    void expectType(Type const& _expectedType);
    /// Checks that this expression is an lvalue and also registers that an address and
    /// not a value is generated during compilation. Can be called after checkTypeRequirements()
    /// by an enclosing expression.
    void requireLValue();
    /// Returns true if @a requireLValue was previously called on this expression.
    bool lvalueRequested() const { return m_lvalueRequested; }

protected:
    //! Inferred type of the expression, only filled after a call to checkTypeRequirements().
    std::shared_ptr<Type const> m_type;
    //! If this expression is an lvalue (i.e. something that can be assigned to).
    //! This is set during calls to @a checkTypeRequirements()
    bool m_isLValue = false;
    //! Whether the outer expression requested the address (true) or the value (false) of this expression.
    bool m_lvalueRequested = false;
};

/// Assignment, can also be a compound assignment.
/// Examples: (a = 7 + 8) or (a *= 2)
class Assignment: public Expression
{
public:
    Assignment(SourceLocation const& _location, ASTPointer<Expression> const& _leftHandSide,
               Token::Value _assignmentOperator, ASTPointer<Expression> const& _rightHandSide):
        Expression(_location), m_leftHandSide(_leftHandSide),
        m_assigmentOperator(_assignmentOperator), m_rightHandSide(_rightHandSide)
    {
        solAssert(Token::isAssignmentOp(_assignmentOperator), "");
    }
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Expression const& getLeftHandSide() const { return *m_leftHandSide; }
    Token::Value getAssignmentOperator() const { return m_assigmentOperator; }
    Expression const& getRightHandSide() const { return *m_rightHandSide; }

private:
    ASTPointer<Expression> m_leftHandSide;
    Token::Value m_assigmentOperator;
    ASTPointer<Expression> m_rightHandSide;
};

/**
 * Operation involving a unary operator, pre- or postfix.
 * Examples: ++i, delete x or !true
 */
class UnaryOperation: public Expression
{
public:
    UnaryOperation(SourceLocation const& _location, Token::Value _operator,
                   ASTPointer<Expression> const& _subExpression, bool _isPrefix):
        Expression(_location), m_operator(_operator),
        m_subExpression(_subExpression), m_isPrefix(_isPrefix)
    {
        solAssert(Token::isUnaryOp(_operator), "");
    }
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Token::Value getOperator() const { return m_operator; }
    bool isPrefixOperation() const { return m_isPrefix; }
    Expression const& getSubExpression() const { return *m_subExpression; }

private:
    Token::Value m_operator;
    ASTPointer<Expression> m_subExpression;
    bool m_isPrefix;
};

/**
 * Operation involving a binary operator.
 * Examples: 1 + 2, true && false or 1 <= 4
 */
class BinaryOperation: public Expression
{
public:
    BinaryOperation(SourceLocation const& _location, ASTPointer<Expression> const& _left,
                    Token::Value _operator, ASTPointer<Expression> const& _right):
        Expression(_location), m_left(_left), m_operator(_operator), m_right(_right)
    {
        solAssert(Token::isBinaryOp(_operator) || Token::isCompareOp(_operator), "");
    }
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Expression const& getLeftExpression() const { return *m_left; }
    Expression const& getRightExpression() const { return *m_right; }
    Token::Value getOperator() const { return m_operator; }
    Type const& getCommonType() const { return *m_commonType; }

private:
    ASTPointer<Expression> m_left;
    Token::Value m_operator;
    ASTPointer<Expression> m_right;

    /// The common type that is used for the operation, not necessarily the result type (e.g. for
    /// comparisons, this is always bool).
    std::shared_ptr<Type const> m_commonType;
};

/**
 * Can be ordinary function call, type cast or struct construction.
 */
class FunctionCall: public Expression
{
public:
    FunctionCall(SourceLocation const& _location, ASTPointer<Expression> const& _expression,
                 std::vector<ASTPointer<Expression>> const& _arguments, std::vector<ASTPointer<ASTString>> const& _names):
        Expression(_location), m_expression(_expression), m_arguments(_arguments), m_names(_names) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Expression const& getExpression() const { return *m_expression; }
    std::vector<ASTPointer<Expression const>> getArguments() const { return {m_arguments.begin(), m_arguments.end()}; }
    std::vector<ASTPointer<ASTString>> const& getNames() const { return m_names; }

    /// Returns true if this is not an actual function call, but an explicit type conversion
    /// or constructor call.
    bool isTypeConversion() const;

private:
    ASTPointer<Expression> m_expression;
    std::vector<ASTPointer<Expression>> m_arguments;
    std::vector<ASTPointer<ASTString>> m_names;
};

/**
 * Expression that creates a new contract, e.g. the "new SomeContract" part in "new SomeContract(1, 2)".
 */
class NewExpression: public Expression
{
public:
    NewExpression(SourceLocation const& _location, ASTPointer<Identifier> const& _contractName):
        Expression(_location), m_contractName(_contractName) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    /// Returns the referenced contract. Can only be called after type checking.
    ContractDefinition const* getContract() const { solAssert(m_contract, ""); return m_contract; }

private:
    ASTPointer<Identifier> m_contractName;

    ContractDefinition const* m_contract = nullptr;
};

/**
 * Access to a member of an object. Example: x.name
 */
class MemberAccess: public Expression
{
public:
    MemberAccess(SourceLocation const& _location, ASTPointer<Expression> _expression,
                 ASTPointer<ASTString> const& _memberName):
        Expression(_location), m_expression(_expression), m_memberName(_memberName) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    Expression const& getExpression() const { return *m_expression; }
    ASTString const& getMemberName() const { return *m_memberName; }
    /// @returns the declaration referenced by this expression. Might return nullptr even if the
    /// expression is valid, e.g. if the member does not correspond to an AST node.
    Declaration const* referencedDeclaration() const { return m_referencedDeclaration; }
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

private:
    ASTPointer<Expression> m_expression;
    ASTPointer<ASTString> m_memberName;

    /// Pointer to the referenced declaration, this is sometimes needed to resolve function over
    /// loads in the type-checking phase.
    Declaration const* m_referencedDeclaration = nullptr;
};

/**
 * Index access to an array. Example: a[2]
 */
class IndexAccess: public Expression
{
public:
    IndexAccess(SourceLocation const& _location, ASTPointer<Expression> const& _base,
                ASTPointer<Expression> const& _index):
        Expression(_location), m_base(_base), m_index(_index) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Expression const& getBaseExpression() const { return *m_base; }
    Expression const* getIndexExpression() const { return m_index.get(); }

private:
    ASTPointer<Expression> m_base;
    ASTPointer<Expression> m_index;
};

/**
 * Primary expression, i.e. an expression that cannot be divided any further. Examples are literals
 * or variable references.
 */
class PrimaryExpression: public Expression
{
public:
    PrimaryExpression(SourceLocation const& _location): Expression(_location) {}
};

/**
 * An identifier, i.e. a reference to a declaration by name like a variable or function.
 */
class Identifier: public PrimaryExpression
{
public:
    Identifier(SourceLocation const& _location, ASTPointer<ASTString> const& _name):
        PrimaryExpression(_location), m_name(_name) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    ASTString const& getName() const { return *m_name; }

    void setReferencedDeclaration(
        Declaration const& _referencedDeclaration,
        ContractDefinition const* _currentContract = nullptr
    )
    {
        m_referencedDeclaration = &_referencedDeclaration;
        m_currentContract = _currentContract;
    }
    Declaration const& getReferencedDeclaration() const;

    /// Stores a set of possible declarations referenced by this identifier. Has to be resolved
    /// providing argument types using overloadResolution before the referenced declaration
    /// is accessed.
    void setOverloadedDeclarations(std::vector<Declaration const*> const& _declarations)
    {
        m_overloadedDeclarations = _declarations;
    }

    /// Tries to find exactly one of the possible referenced declarations provided the given
    /// argument types in a call context.
    void overloadResolution(TypePointers const& _argumentTypes);

private:
    ASTPointer<ASTString> m_name;

    /// Declaration the name refers to.
    Declaration const* m_referencedDeclaration = nullptr;
    /// Stores a reference to the current contract. This is needed because types of base contracts
    /// change depending on the context.
    ContractDefinition const* m_currentContract = nullptr;
    /// A vector of overloaded declarations, right now only FunctionDefinition has overloaded declarations.
    std::vector<Declaration const*> m_overloadedDeclarations;
};

/**
 * An elementary type name expression is used in expressions like "a = uint32(2)" to change the
 * type of an expression explicitly. Here, "uint32" is the elementary type name expression and
 * "uint32(2)" is a @ref FunctionCall.
 */
class ElementaryTypeNameExpression: public PrimaryExpression
{
public:
    ElementaryTypeNameExpression(SourceLocation const& _location, Token::Value _typeToken):
        PrimaryExpression(_location), m_typeToken(_typeToken)
    {
        solAssert(Token::isElementaryTypeName(_typeToken), "");
    }
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Token::Value getTypeToken() const { return m_typeToken; }

private:
    Token::Value m_typeToken;
};

/**
 * A literal string or number. @see ExpressionCompiler::endVisit() is used to actually parse its value.
 */
class Literal: public PrimaryExpression
{
public:
    enum class SubDenomination
    {
        None = Token::Illegal,
        Wei = Token::SubWei,
        Szabo = Token::SubSzabo,
        Finney = Token::SubFinney,
        Ether = Token::SubEther,
        Second = Token::SubSecond,
        Minute = Token::SubMinute,
        Hour = Token::SubHour,
        Day = Token::SubDay,
        Week = Token::SubWeek,
        Year = Token::SubYear
    };
    Literal(SourceLocation const& _location, Token::Value _token,
            ASTPointer<ASTString> const& _value,
            SubDenomination _sub = SubDenomination::None):
        PrimaryExpression(_location), m_token(_token), m_value(_value), m_subDenomination(_sub) {}
    virtual void accept(ASTVisitor& _visitor) override;
    virtual void accept(ASTConstVisitor& _visitor) const override;
    virtual void checkTypeRequirements(TypePointers const* _argumentTypes) override;

    Token::Value getToken() const { return m_token; }
    /// @returns the non-parsed value of the literal
    ASTString const& getValue() const { return *m_value; }

    SubDenomination getSubDenomination() const { return m_subDenomination; }

private:
    Token::Value m_token;
    ASTPointer<ASTString> m_value;
    SubDenomination m_subDenomination;
};

/// @}


}
}