zeek/src/Type.h

// See the file "COPYING" in the main distribution directory for copyright.

#pragma once

#include <list>
#include <map>
#include <memory>
#include <optional>
#include <set>
#include <string>
#include <unordered_map>

#include "zeek/Attr.h"
#include "zeek/ID.h"
#include "zeek/IntrusivePtr.h"
#include "zeek/Obj.h"
#include "zeek/Traverse.h"
#include "zeek/ZeekList.h"

namespace zeek {

class Val;
union ZVal;
class EnumVal;
class RecordVal;
class TableVal;
using ValPtr = IntrusivePtr<Val>;
using EnumValPtr = IntrusivePtr<EnumVal>;
using TableValPtr = IntrusivePtr<TableVal>;

namespace detail {

class Attributes;
class CompositeHash;
class Expr;
class ListExpr;
class ZAMCompiler;
class CPPRuntime;

using ExprPtr = IntrusivePtr<Expr>;
using ListExprPtr = IntrusivePtr<ListExpr>;

// The following tracks how to initialize a given record field.
class FieldInit {
public:
    virtual ~FieldInit() {}

    // Return the initialization value of the field.
    virtual ZVal Generate() const = 0;

    // Can initialization of the field be deferred?
    virtual bool IsDeferrable() const { return true; }

    // Returns the expression evaluated to initialize the field, if any.
    // (Used for script optimization.)
    virtual ExprPtr InitExpr() const;
};

} // namespace detail

// Zeek types.
enum TypeTag : uint8_t {
    TYPE_VOID,     // 0
    TYPE_BOOL,     // 1
    TYPE_INT,      // 2
    TYPE_COUNT,    // 3
    TYPE_DOUBLE,   // 4
    TYPE_TIME,     // 5
    TYPE_INTERVAL, // 6
    TYPE_STRING,   // 7
    TYPE_PATTERN,  // 8
    TYPE_ENUM,     // 9
    TYPE_PORT,     // 10
    TYPE_ADDR,     // 11
    TYPE_SUBNET,   // 12
    TYPE_ANY,      // 13
    TYPE_TABLE,    // 14
    TYPE_RECORD,   // 15
    TYPE_LIST,     // 16
    TYPE_FUNC,     // 17
    TYPE_FILE,     // 18
    TYPE_VECTOR,   // 19
    TYPE_OPAQUE,   // 20
    TYPE_TYPE,     // 21
    TYPE_ERROR     // 22
#define NUM_TYPES (int(TYPE_ERROR) + 1)
};

// Returns the name of the type.
extern const char* type_name(TypeTag t);

constexpr bool is_network_order(TypeTag tag) noexcept { return tag == TYPE_PORT; }

enum FunctionFlavor : uint8_t { FUNC_FLAVOR_FUNCTION, FUNC_FLAVOR_EVENT, FUNC_FLAVOR_HOOK };

enum InternalTypeTag : uint8_t {
    TYPE_INTERNAL_VOID,
    TYPE_INTERNAL_INT,
    TYPE_INTERNAL_UNSIGNED,
    TYPE_INTERNAL_DOUBLE,
    TYPE_INTERNAL_STRING,
    TYPE_INTERNAL_ADDR,
    TYPE_INTERNAL_SUBNET,
    TYPE_INTERNAL_OTHER,
    TYPE_INTERNAL_ERROR
};

constexpr InternalTypeTag to_internal_type_tag(TypeTag tag) noexcept {
    switch ( tag ) {
        case TYPE_VOID: return TYPE_INTERNAL_VOID;

        case TYPE_BOOL:
        case TYPE_INT:
        case TYPE_ENUM: return TYPE_INTERNAL_INT;

        case TYPE_COUNT:
        case TYPE_PORT: return TYPE_INTERNAL_UNSIGNED;

        case TYPE_DOUBLE:
        case TYPE_TIME:
        case TYPE_INTERVAL: return TYPE_INTERNAL_DOUBLE;

        case TYPE_STRING: return TYPE_INTERNAL_STRING;

        case TYPE_ADDR: return TYPE_INTERNAL_ADDR;

        case TYPE_SUBNET: return TYPE_INTERNAL_SUBNET;

        case TYPE_PATTERN:
        case TYPE_ANY:
        case TYPE_TABLE:
        case TYPE_RECORD:
        case TYPE_LIST:
        case TYPE_FUNC:
        case TYPE_FILE:
        case TYPE_OPAQUE:
        case TYPE_VECTOR:
        case TYPE_TYPE: return TYPE_INTERNAL_OTHER;

        case TYPE_ERROR: return TYPE_INTERNAL_ERROR;
    }

    /* this should be unreachable */
    return TYPE_INTERNAL_VOID;
}

class Type;
class TypeList;
class TableType;
class SetType;
class RecordType;
class FuncType;
class EnumType;
class VectorType;
class TypeType;
class OpaqueType;
class FileType;

using TypePtr = IntrusivePtr<Type>;
using TypeListPtr = IntrusivePtr<TypeList>;
using TableTypePtr = IntrusivePtr<TableType>;
using SetTypePtr = IntrusivePtr<SetType>;
using RecordTypePtr = IntrusivePtr<RecordType>;
using FuncTypePtr = IntrusivePtr<FuncType>;
using EnumTypePtr = IntrusivePtr<EnumType>;
using VectorTypePtr = IntrusivePtr<VectorType>;
using TypeTypePtr = IntrusivePtr<TypeType>;
using OpaqueTypePtr = IntrusivePtr<OpaqueType>;
using FileTypePtr = IntrusivePtr<FileType>;

constexpr int DOES_NOT_MATCH_INDEX = 0;
constexpr int MATCHES_INDEX_SCALAR = 1;
constexpr int MATCHES_INDEX_VECTOR = 2;

class Type : public Obj {
public:
    static inline const TypePtr nil;

    explicit Type(TypeTag tag, bool base_type = false);

    // Performs a shallow clone operation of the Zeek type.
    // This especially means that especially for tables the types
    // are not recursively cloned; altering one type will in this case
    // alter one of them.
    // The main use for this is alias tracking.
    // Clone operations will mostly be implemented in the derived classes;
    // in addition cloning will be limited to classes that can be reached by
    // the script-level.
    virtual TypePtr ShallowClone();

    TypeTag Tag() const { return tag; }
    InternalTypeTag InternalType() const { return internal_tag; }

    // Whether it's stored in network order.
    bool IsNetworkOrder() const { return is_network_order; }

    // Type-checks the given expression list, returning
    // MATCHES_INDEX_SCALAR = 1 if it matches this type's index
    // and produces a scalar result (and promoting its
    // subexpressions as necessary); MATCHES_INDEX_VECTOR = 2
    // if it matches and produces a vector result; and
    // DOES_NOT_MATCH_INDEX = 0 if it can't match (or the type
    // is not an indexable type).
    virtual int MatchesIndex(detail::ListExpr* index) const;

    // Returns the type yielded by this type.  For example, if
    // this type is a table[string] of port, then returns the "port"
    // type.  Returns nil if this is not an index type.
    virtual const TypePtr& Yield() const;

    const TypeList* AsTypeList() const;
    TypeList* AsTypeList();

    const TableType* AsTableType() const;
    TableType* AsTableType();

    [[deprecated("Remove in v9.1. Use AsTableType() instead.")]]
    const SetType* AsSetType() const;

    [[deprecated("Remove in v9.1. Use AsTableType() instead.")]]
    SetType* AsSetType();

    const RecordType* AsRecordType() const;
    RecordType* AsRecordType();

    const FuncType* AsFuncType() const;
    FuncType* AsFuncType();

    const FileType* AsFileType() const;
    FileType* AsFileType();

    const EnumType* AsEnumType() const;
    EnumType* AsEnumType();

    const VectorType* AsVectorType() const;
    VectorType* AsVectorType();

    const OpaqueType* AsOpaqueType() const;
    OpaqueType* AsOpaqueType();

    const TypeType* AsTypeType() const;
    TypeType* AsTypeType();

    bool IsSet() const { return tag == TYPE_TABLE && ! Yield(); }

    bool IsTable() const { return tag == TYPE_TABLE && Yield(); }

    Type* Ref() {
        ::zeek::Ref(this);
        return this;
    }

    void Describe(ODesc* d) const override;
    virtual void DescribeReST(ODesc* d, bool roles_only = false) const;

    void SetName(const std::string& arg_name) { name = arg_name; }
    const std::string& GetName() const { return name; }

    virtual detail::TraversalCode Traverse(detail::TraversalCallback* cb) const;

    struct TypePtrComparer {
        bool operator()(const TypePtr& a, const TypePtr& b) const { return a.get() < b.get(); }
    };
    using TypePtrSet = std::set<TypePtr, TypePtrComparer>;
    using TypeAliasMap = std::map<std::string, TypePtrSet, std::less<>>;

    /**
     * Returns a mapping of type-name to all other type names declared as
     * an alias to it.
     */
    static const TypeAliasMap& GetAliasMap() { return type_aliases; }

    /**
     * Returns true if the given type name has any declared aliases
     */
    static bool HasAliases(std::string_view type_name) {
        return Type::type_aliases.find(type_name) != Type::type_aliases.end();
    }

    /**
     * Returns the set of all type names declared as an aliases to the given
     * type name.  A static empty set is returned if there are no aliases.
     */
    static const TypePtrSet& Aliases(std::string_view type_name) {
        static TypePtrSet empty;
        auto it = Type::type_aliases.find(type_name);
        return it == Type::type_aliases.end() ? empty : it->second;
    }

    /**
     * Registers a new type alias.
     * @param type_name  the name of the type to register a new alias for.
     * @param type  the associated alias type of *type_name*.
     * @return  true if the alias is now registered or false if the alias was
     * already previously registered.
     */
    static bool RegisterAlias(std::string_view type_name, TypePtr type) {
        auto it = Type::type_aliases.find(type_name);
        if ( it == Type::type_aliases.end() )
            it = Type::type_aliases.emplace(std::string{type_name}, TypePtrSet{}).first;
        return it->second.emplace(std::move(type)).second;
    }

protected:
    virtual void DoDescribe(ODesc* d) const;

    Type() = default;

    void SetError();

private:
    TypeTag tag;
    InternalTypeTag internal_tag;
    bool is_network_order;
    bool base_type;
    std::string name;

    static TypeAliasMap type_aliases;
};

class TypeList final : public Type {
public:
    explicit TypeList(TypePtr arg_pure_type = nullptr) : Type(TYPE_LIST), pure_type(std::move(arg_pure_type)) {}

    ~TypeList() override = default;

    const std::vector<TypePtr>& GetTypes() const { return types; }

    bool IsPure() const { return pure_type != nullptr; }

    // Returns the underlying pure type, or nil if the list
    // is not pure or is empty.
    const TypePtr& GetPureType() const { return pure_type; }

    // Retrospectively instantiates an underlying pure type, if in
    // fact each element has the same type.
    void CheckPure();

    // True if all of the types match t, false otherwise.  If
    // is_init is true, then the matching is done in the context
    // of an initialization.
    bool AllMatch(const Type* t, bool is_init) const;
    bool AllMatch(const TypePtr& t, bool is_init) const { return AllMatch(t.get(), is_init); }

    void Append(TypePtr t);
    void AppendEvenIfNotPure(TypePtr t);

    // Resets the list to be empty.
    void Clear() { types.clear(); }

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    void DoDescribe(ODesc* d) const override;

    TypePtr pure_type;
    std::vector<TypePtr> types;
};

class IndexType : public Type {
public:
    ~IndexType() override = default;

    int MatchesIndex(detail::ListExpr* index) const override;

    const TypeListPtr& GetIndices() const { return indices; }

    const std::vector<TypePtr>& GetIndexTypes() const { return indices->GetTypes(); }

    const TypePtr& Yield() const override { return yield_type; }

    void DescribeReST(ODesc* d, bool roles_only = false) const override;

    // Returns true if this table is solely indexed by subnet.
    bool IsSubNetIndex() const { return is_subnet_index; }

    // Returns true if this table has a single index of type pattern.
    bool IsPatternIndex() const { return is_pattern_index; }

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    IndexType(TypeTag t, TypeListPtr arg_indices, TypePtr arg_yield_type)
        : Type(t), indices(std::move(arg_indices)), yield_type(std::move(arg_yield_type)) {
        // "indices" might be nil if we're deferring construction of the type
        // for "-O use-C++" initialization.
        if ( indices )
            SetSpecialIndices();
        else
            is_subnet_index = is_pattern_index = false; // placeholders
    }

    void SetSpecialIndices() {
        const auto& types = indices->GetTypes();
        is_subnet_index = types.size() == 1 && types[0]->Tag() == TYPE_SUBNET;
        is_pattern_index = types.size() == 1 && types[0]->Tag() == TYPE_PATTERN;
    }

    void DoDescribe(ODesc* d) const override;

    TypeListPtr indices;
    TypePtr yield_type;

    bool is_subnet_index;
    bool is_pattern_index;
};

class TableType : public IndexType {
public:
    TableType(TypeListPtr ind, TypePtr yield);

    ~TableType() override;

    /**
     * Assesses whether an &expire_func attribute's function type is compatible
     * with this table type.
     * @param attr  the &expire_func attribute to check (this method must not be
     * called with other type of attributes).
     * @return  true if compatible, false if not
     */
    bool CheckExpireFuncCompatibility(const detail::AttrPtr& attr);

    TypePtr ShallowClone() override;

    // Returns true if this table type is "unspecified", which is
    // what one gets using an empty "set()" or "table()" constructor.
    bool IsUnspecifiedTable() const;

    const detail::CompositeHash* GetTableHash() const { return table_hash.get(); }

    // Called to rebuild the associated hash function when a record type
    // (that this table type depends on) gets redefined during parsing.
    void RegenerateHash();

private:
    bool DoExpireCheck(const detail::AttrPtr& attr);

    std::unique_ptr<detail::CompositeHash> table_hash;

    // Used to prevent repeated error messages.
    bool reported_error = false;
};

class [[deprecated("Remove in v9.1. Use TableType instead.")]] SetType final : public TableType {
public:
    SetType(TypeListPtr ind, detail::ListExprPtr arg_elements);
    ~SetType() override;

    TypePtr ShallowClone() override;

    const detail::ListExprPtr& Elements() const { return elements; }

protected:
    detail::ListExprPtr elements;
};

class FuncType final : public Type {
public:
    static inline const FuncTypePtr nil;

    /**
     * Prototype is only currently used for events and hooks which declare
     * multiple signature prototypes that allow users to have handlers
     * with various argument permutations.
     */
    struct Prototype {
        bool deprecated;
        std::string deprecation_msg;
        RecordTypePtr args;
        // Maps from parameter index in canonical prototype to
        // parameter index in this alternate prototype.
        std::map<int, int> offsets;
    };

    FuncType(RecordTypePtr args, TypePtr yield, FunctionFlavor f);

    TypePtr ShallowClone() override;

    const RecordTypePtr& Params() const { return args; }

    const TypePtr& Yield() const override { return yield; }

    void SetYieldType(TypePtr arg_yield) { yield = std::move(arg_yield); }
    FunctionFlavor Flavor() const { return flavor; }
    std::string FlavorString() const;

    // Used to convert a function type to an event or hook type.
    void ClearYieldType(FunctionFlavor arg_flav) {
        yield = nullptr;
        flavor = arg_flav;
    }

    int MatchesIndex(detail::ListExpr* index) const override;
    bool CheckArgs(const TypePList* args, bool is_init = false, bool do_warn = true) const;
    bool CheckArgs(const std::vector<TypePtr>& args, bool is_init = false, bool do_warn = true) const;

    const TypeListPtr& ParamList() const { return arg_types; }

    void DescribeReST(ODesc* d, bool roles_only = false) const override;

    /**
     * Adds a new event/hook signature allowed for use in handlers.
     */
    void AddPrototype(Prototype s);

    /**
     * Returns a prototype signature that matches the desired argument types.
     */
    std::optional<Prototype> FindPrototype(const RecordType& args) const;

    /**
     * Returns all allowed function prototypes.
     */
    const std::vector<Prototype>& Prototypes() const { return prototypes; }

    /**
     * A single lambda "capture" (outer variable used in a lambda's body).
     */
    class Capture {
    public:
        Capture(detail::IDPtr _id, bool _deep_copy);

        Capture(const Capture&) = default;
        Capture(Capture&&) = default;
        Capture& operator=(const Capture&) = default;
        Capture& operator=(Capture&&) = default;
        ~Capture() = default;

        auto& Id() const { return id; }
        bool IsDeepCopy() const { return deep_copy; }
        bool IsManaged() const { return is_managed; }

        // For script optimization:
        void SetID(detail::IDPtr new_id) { id = std::move(new_id); }

    private:
        detail::IDPtr id;
        bool deep_copy;
        bool is_managed;
    };

    using CaptureList = std::vector<Capture>;

    /**
     * Sets this function's set of captures.  Only valid for lambdas.
     *
     * @param captures  if non-nil, a list of the lambda's captures
     */
    void SetCaptures(std::optional<CaptureList> captures);

    /**
     * Returns the captures declared for this function, or nil if none.
     *
     * @return a vector giving the captures
     */
    const std::optional<CaptureList>& GetCaptures() const { return captures; }

    /**
     * Returns whether it's acceptable for a "return" inside the function
     * to not have an expression (even though the function has a return
     * type).  Used internally for lambdas built for "when" statements.
     */
    bool ExpressionlessReturnOkay() const { return expressionless_return_okay; }

    /**
     * Sets whether it's acceptable for a "return" inside the function
     * to not have an expression (even though the function has a return
     * type).  Used internally for lambdas built for "when" statements.
     */
    void SetExpressionlessReturnOkay(bool is_ok) { expressionless_return_okay = is_ok; }

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    friend FuncTypePtr make_intrusive<FuncType>();

    FuncType() : Type(TYPE_FUNC) { flavor = FUNC_FLAVOR_FUNCTION; }

    void DoDescribe(ODesc* d) const override;

    RecordTypePtr args;
    TypeListPtr arg_types;
    TypePtr yield;
    FunctionFlavor flavor;
    std::vector<Prototype> prototypes;

    std::optional<CaptureList> captures; // if nil then no captures specified
    // Used for internal lambdas built for "when" statements:
    bool expressionless_return_okay = false;

    // Used to prevent repeated error messages.
    bool reported_error = false;
};

class TypeType final : public Type {
public:
    explicit TypeType(TypePtr t) : zeek::Type(TYPE_TYPE), type(std::move(t)) {}
    TypePtr ShallowClone() override { return make_intrusive<TypeType>(type); }

    const TypePtr& GetType() const { return type; }

    template<class T>
    IntrusivePtr<T> GetType() const {
        return cast_intrusive<T>(type);
    }

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    TypePtr type;
};

class TypeDecl final {
public:
    TypeDecl() = default;
    TypeDecl(const char* i, TypePtr t, detail::AttributesPtr attrs = nullptr);
    TypeDecl(const TypeDecl& other);
    ~TypeDecl();

    TypeDecl& operator=(const TypeDecl& other);

    const detail::AttrPtr& GetAttr(detail::AttrTag a) const { return attrs ? attrs->Find(a) : detail::Attr::nil; }

    const detail::Location* GetLocationInfo() const { return &loc; }

    void DescribeReST(ODesc* d, bool roles_only = false) const;

    TypePtr type;
    detail::AttributesPtr attrs;
    const char* id = nullptr;

private:
    detail::Location loc = detail::GetCurrentLocation();
};

using type_decl_list = PList<TypeDecl>;

class RecordType final : public Type {
public:
    explicit RecordType(type_decl_list* types);
    TypePtr ShallowClone() override;

    ~RecordType() override;

    bool HasField(const char* field) const;

    /**
     * Looks up a field by name and returns its type.  No check for invalid
     * field name is performed.
     */
    const TypePtr& GetFieldType(const char* field_name) const { return GetFieldType(FieldOffset(field_name)); }

    /**
     * Looks up a field by name and returns its type as cast to @c T.
     * No check for invalid field name is performed.
     */
    template<class T>
    IntrusivePtr<T> GetFieldType(const char* field_name) const {
        return cast_intrusive<T>(GetFieldType(field_name));
    }

    /**
     * Looks up a field by its index and returns its type.  No check for
     * invalid field offset is performed.
     */
    const TypePtr& GetFieldType(int field_index) const { return (*types)[field_index]->type; }

    /**
     * Looks up a field by its index and returns its type as cast to @c T.
     * No check for invalid field offset is performed.
     */
    template<class T>
    IntrusivePtr<T> GetFieldType(int field_index) const {
        return cast_intrusive<T>((*types)[field_index]->type);
    }

    ValPtr FieldDefault(int field) const;

    // A field's offset is its position in the type_decl_list,
    // starting at 0.  Returns negative if the field doesn't exist.
    int FieldOffset(const char* field) const;

    // Given an offset, returns the field's name.
    const char* FieldName(int field) const;

    const type_decl_list* Types() const { return types; }
    type_decl_list* Types() { return types; }

    // Given an offset, returns the field's TypeDecl.
    const TypeDecl* FieldDecl(int field) const;
    TypeDecl* FieldDecl(int field);

    // Returns flags corresponding to which fields in the record
    // have types requiring memory management (reference counting).
    const std::vector<bool>& ManagedFields() const { return managed_fields; }

    int NumFields() const { return num_fields; }
    int NumOrigFields() const { return num_orig_fields; }

    /**
     * Returns a "record_field_table" value for introspection purposes.
     * @param rv  an optional record value, if given the values of
     * all fields will be provided in the returned table. The table
     * is initialized with the &ordered attribute such that iterating over
     * the table will yield entries for fields in the same order as they
     * are kept in the record type types list.
     */
    TableValPtr GetRecordFieldsVal(const RecordVal* rv = nullptr) const;

    // Returns null if all is ok, otherwise a pointer to an error message.
    const char* AddFields(const type_decl_list& types, bool add_log_attr = false);

    void AddFieldsDirectly(const type_decl_list& types, bool add_log_attr = false);

    void DescribeReST(ODesc* d, bool roles_only = false) const override;
    void DescribeFields(ODesc* d, bool func_args = false) const;
    void DescribeFieldsReST(ODesc* d, bool func_args) const;

    bool IsFieldDeprecated(int field) const {
        const TypeDecl* decl = FieldDecl(field);
        return decl && decl->GetAttr(detail::ATTR_DEPRECATED) != nullptr;
    }

    bool FieldHasAttr(int field, detail::AttrTag at) const {
        const TypeDecl* decl = FieldDecl(field);
        return decl && decl->GetAttr(at) != nullptr;
    }

    std::string GetFieldDeprecationWarning(int field, bool has_check) const;

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

    // Can initialization of record values of this type be deferred?
    //
    // When record types contain non-const &default expressions or recursively
    // contain any nested records that themselves are not deferrable,
    // initialization can not be deferred, otherwise possible.
    bool IsDeferrable() const;

    // Whether values of this record type are equivalent upon initial
    // creation, or might differ (e.g. due to function calls or changes
    // to global state) - used for script optimization.
    bool IdempotentCreation() const { return creation_inits.empty(); }

    static void InitPostScript();

private:
    RecordType() { types = nullptr; }

    void AddField(unsigned int field, const TypeDecl* td);

    void DoDescribe(ODesc* d) const override;

    // Field initializations that can be deferred to first access,
    // beneficial for fields that are separately initialized prior
    // to first access.  Nil pointers mean "skip initializing the field".
    std::vector<std::shared_ptr<detail::FieldInit>> deferred_inits;

    // Field initializations that need to be done upon record creation,
    // rather than deferred.  These are expressions whose value might
    // change if computed later.
    //
    // Such initializations are uncommon, so we represent them using
    // <fieldoffset, init> pairs.
    std::vector<std::pair<int, std::shared_ptr<detail::FieldInit>>> creation_inits;

    class CreationInitsOptimizer;
    friend zeek::RecordVal;
    friend zeek::detail::ZAMCompiler;
    friend zeek::detail::CPPRuntime;
    const auto& DeferredInits() const { return deferred_inits; }
    const auto& CreationInits() const { return creation_inits; }

    // If we were willing to bound the size of records, then we could
    // use std::bitset here instead.
    std::vector<bool> managed_fields;

    // Number of fields in the type.
    int num_fields = 0;

    // Number of fields in the type when originally declared.
    int num_orig_fields = 0;

    type_decl_list* types = nullptr;
    std::set<std::string> field_ids;
};

class FileType final : public Type {
public:
    explicit FileType(TypePtr yield_type);
    TypePtr ShallowClone() override { return make_intrusive<FileType>(yield); }
    ~FileType() override;

    const TypePtr& Yield() const override { return yield; }

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    void DoDescribe(ODesc* d) const override;

    TypePtr yield;
};

class OpaqueType final : public Type {
public:
    explicit OpaqueType(const std::string& name);
    TypePtr ShallowClone() override { return make_intrusive<OpaqueType>(name); }
    ~OpaqueType() override {};

    const std::string& Name() const { return name; }

    void DescribeReST(ODesc* d, bool roles_only = false) const override;

protected:
    OpaqueType() {}

    void DoDescribe(ODesc* d) const override;

    std::string name;
};

class EnumType final : public Type {
public:
    using enum_name_list = std::list<std::pair<std::string, zeek_int_t>>;

    explicit EnumType(const EnumType* e);
    explicit EnumType(const std::string& arg_name);
    TypePtr ShallowClone() override;
    ~EnumType() override;

    // The value of this name is next internal counter value, starting
    // with zero. The internal counter is incremented.
    void AddName(const std::string& module_name, const char* name, bool is_export, detail::Expr* deprecation = nullptr,
                 bool from_redef = false);

    // The value of this name is set to val. Once a value has been
    // explicitly assigned using this method, no further names can be
    // added that aren't likewise explicitly initialized.
    void AddName(const std::string& module_name, const char* name, zeek_int_t val, bool is_export,
                 detail::Expr* deprecation = nullptr, bool from_redef = false);

    // -1 indicates not found.  Second version is for full names
    // that already incorporate the module.
    zeek_int_t Lookup(const std::string& module_name, const char* name) const;
    zeek_int_t Lookup(const std::string& full_name) const;

    const char* Lookup(zeek_int_t value) const; // Returns 0 if not found

    // Returns the list of defined names with their values. The names
    // will be fully qualified with their module name.
    enum_name_list Names() const;

    bool HasRedefs() const { return has_redefs; }

    void DescribeReST(ODesc* d, bool roles_only = false) const override;

    const EnumValPtr& GetEnumVal(zeek_int_t i);

    // Only for use by C++-generated code.  Non-protected because we
    // don't know in advance the names of the functions that will
    // access it.
    void AddNameInternal(const std::string& full_name, zeek_int_t val);

protected:
    void AddNameInternal(const std::string& module_name, const char* name, zeek_int_t val, bool is_export);

    void CheckAndAddName(const std::string& module_name, const char* name, zeek_int_t val, bool is_export,
                         detail::Expr* deprecation = nullptr, bool from_redef = false);

    void DoDescribe(ODesc* d) const override;

    std::map<std::string, zeek_int_t> names;
    std::map<zeek_int_t, std::string> rev_names;

    // Whether any of the elements of the enum were added via redef's.
    bool has_redefs = false;

    std::unordered_map<zeek_int_t, EnumValPtr> vals;

    // The counter is initialized to 0 and incremented on every implicit
    // auto-increment name that gets added (thus its > 0 if
    // auto-increment is used).  Once an explicit value has been
    // specified, the counter is set to -1. This way counter can be used
    // as a flag to prevent mixing of auto-increment and explicit
    // enumerator specifications.
    zeek_int_t counter;
};

class VectorType final : public Type {
public:
    explicit VectorType(TypePtr t);
    TypePtr ShallowClone() override;
    ~VectorType() override;

    const TypePtr& Yield() const override;

    int MatchesIndex(detail::ListExpr* index) const override;

    // Returns true if this table type is "unspecified", which is what one
    // gets using an empty "vector()" constructor.
    bool IsUnspecifiedVector() const;

    void DescribeReST(ODesc* d, bool roles_only = false) const override;

    detail::TraversalCode Traverse(detail::TraversalCallback* cb) const override;

protected:
    void DoDescribe(ODesc* d) const override;

    TypePtr yield_type;
};

// True if the two types are equivalent.  If is_init is true then the test is
// done in the context of an initialization. If match_record_field_names is
// true then for record types the field names have to match, too.
extern bool same_type(const Type& t1, const Type& t2, bool is_init = false, bool match_record_field_names = true);
inline bool same_type(const TypePtr& t1, const TypePtr& t2, bool is_init = false,
                      bool match_record_field_names = true) {
    // If the pointers are identical, the type should be the same type.
    if ( t1.get() == t2.get() )
        return true;

    return same_type(*t1, *t2, is_init, match_record_field_names);
}
inline bool same_type(const Type* t1, const Type* t2, bool is_init = false, bool match_record_field_names = true) {
    // If the pointers are identical, the type should be the same type.
    if ( t1 == t2 )
        return true;

    return same_type(*t1, *t2, is_init, match_record_field_names);
}
inline bool same_type(const TypePtr& t1, const Type* t2, bool is_init = false, bool match_record_field_names = true) {
    // If the pointers are identical, the type should be the same type.
    if ( t1.get() == t2 )
        return true;

    return same_type(*t1, *t2, is_init, match_record_field_names);
}
inline bool same_type(const Type* t1, const TypePtr& t2, bool is_init = false, bool match_record_field_names = true) {
    // If the pointers are identical, the type should be the same type.
    if ( t1 == t2.get() )
        return true;

    return same_type(*t1, *t2, is_init, match_record_field_names);
}

// True if the two attribute lists are equivalent.
extern bool same_attrs(const detail::Attributes* a1, const detail::Attributes* a2);

// Returns true if the record sub_rec can be promoted to the record
// super_rec.
extern bool record_promotion_compatible(const RecordType* super_rec, const RecordType* sub_rec);

// If the given Type is a TypeList with just one element, returns
// that element, otherwise returns the type.
extern const Type* flatten_type(const Type* t);
extern Type* flatten_type(Type* t);

// Returns the "maximum" of two type tags, in a type-promotion sense.
extern TypeTag max_type(TypeTag t1, TypeTag t2);

// Given two types, returns the "merge", in which promotable types
// are promoted to the maximum of the two.  Returns nil (and generates
// an error message) if the types are incompatible.
TypePtr merge_types(const TypePtr& t1, const TypePtr& t2);

// Given a list of expressions, returns the maximal type consistent across
// all of them, or nil if this cannot be done.  "Maximal" incorporates
// notions of arithmetic coercion, but otherwise requires type-equivalence.
TypePtr maximal_type(detail::ListExpr* elements);

// Given an expression, infer its type when used for an initialization.
TypePtr init_type(const detail::ExprPtr& init);

// Returns true if argument is an atomic type.
bool is_atomic_type(const Type& t);
inline bool is_atomic_type(const Type* t) { return is_atomic_type(*t); }
inline bool is_atomic_type(const TypePtr& t) { return is_atomic_type(*t); }

// True if the given type tag corresponds to type that can be assigned to.
extern bool is_assignable(TypeTag t);
inline bool is_assignable(Type* t) { return is_assignable(t->Tag()); }

// True if the given type tag corresponds to an integral type.
inline bool IsIntegral(TypeTag t) { return (t == TYPE_INT || t == TYPE_COUNT); }

// True if the given type tag corresponds to an arithmetic type.
inline bool IsArithmetic(TypeTag t) { return (IsIntegral(t) || t == TYPE_DOUBLE); }

// True if the given type tag corresponds to a boolean type.
inline bool IsBool(TypeTag t) { return (t == TYPE_BOOL); }

// True if the given type tag corresponds to an interval type.
inline bool IsInterval(TypeTag t) { return (t == TYPE_INTERVAL); }

// True if the given type tag corresponds to a record type.
inline bool IsRecord(TypeTag t) { return (t == TYPE_RECORD); }

// True if the given type tag corresponds to a function type.
inline bool IsFunc(TypeTag t) { return (t == TYPE_FUNC); }

// True if the given type tag is a vector.
inline bool IsVector(TypeTag t) { return (t == TYPE_VECTOR); }

// True if the given type tag is a string.
inline bool IsString(TypeTag t) { return (t == TYPE_STRING); }

// True if the given type is an aggregate.
inline bool IsAggr(TypeTag tag) { return tag == TYPE_VECTOR || tag == TYPE_TABLE || tag == TYPE_RECORD; }
inline bool IsAggr(const Type* t) { return IsAggr(t->Tag()); }
inline bool IsAggr(const TypePtr& t) { return IsAggr(t->Tag()); }

// True if the given type is a container.
inline bool IsContainer(TypeTag tag) { return tag == TYPE_VECTOR || tag == TYPE_TABLE; }

// True if the given type tag corresponds to the error type.
inline bool IsErrorType(TypeTag t) { return (t == TYPE_ERROR); }

// True if both tags are integral types.
inline bool BothIntegral(TypeTag t1, TypeTag t2) { return (IsIntegral(t1) && IsIntegral(t2)); }

// True if both tags are arithmetic types.
inline bool BothArithmetic(TypeTag t1, TypeTag t2) { return (IsArithmetic(t1) && IsArithmetic(t2)); }

// True if either tags is an arithmetic type.
inline bool EitherArithmetic(TypeTag t1, TypeTag t2) { return (IsArithmetic(t1) || IsArithmetic(t2)); }

// True if both tags are boolean types.
inline bool BothBool(TypeTag t1, TypeTag t2) { return (IsBool(t1) && IsBool(t2)); }

// True if both tags are interval types.
inline bool BothInterval(TypeTag t1, TypeTag t2) { return (IsInterval(t1) && IsInterval(t2)); }

// True if both tags are string types.
inline bool BothString(TypeTag t1, TypeTag t2) { return (IsString(t1) && IsString(t2)); }

// True if either tag is the error type.
inline bool EitherError(TypeTag t1, TypeTag t2) { return (IsErrorType(t1) || IsErrorType(t2)); }

// Returns the basic (non-parameterized) type with the given type.
const TypePtr& base_type(TypeTag tag);

// Returns the basic error type.
inline const TypePtr& error_type() { return base_type(TYPE_ERROR); }

} // namespace zeek

extern zeek::OpaqueTypePtr md5_type;
extern zeek::OpaqueTypePtr sha1_type;
extern zeek::OpaqueTypePtr sha256_type;
extern zeek::OpaqueTypePtr entropy_type;
extern zeek::OpaqueTypePtr cardinality_type;
extern zeek::OpaqueTypePtr topk_type;
extern zeek::OpaqueTypePtr bloomfilter_type;
extern zeek::OpaqueTypePtr x509_opaque_type;
extern zeek::OpaqueTypePtr ocsp_resp_opaque_type;
extern zeek::OpaqueTypePtr paraglob_type;
extern zeek::OpaqueTypePtr counter_metric_type;
extern zeek::OpaqueTypePtr counter_metric_family_type;
extern zeek::OpaqueTypePtr gauge_metric_type;
extern zeek::OpaqueTypePtr gauge_metric_family_type;
extern zeek::OpaqueTypePtr histogram_metric_type;
extern zeek::OpaqueTypePtr histogram_metric_family_type;