pub const Type = union(enum) {
    type: void,
    void: void,
    bool: void,
    noreturn: void,
    int: Int,
    float: Float,
    pointer: Pointer,
    array: Array,
    @"struct": Struct,
    comptime_float: void,
    comptime_int: void,
    undefined: void,
    null: void,
    optional: Optional,
    error_union: ErrorUnion,
    error_set: ErrorSet,
    @"enum": Enum,
    @"union": Union,
    @"fn": Fn,
    @"opaque": Opaque,
    frame: Frame,
    @"anyframe": AnyFrame,
    vector: Vector,
    enum_literal: void,

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Int = struct {
        signedness: Signedness,
        bits: u16,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Float = struct {
        bits: u16,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Pointer = struct {
        size: Size,
        is_const: bool,
        is_volatile: bool,
        /// TODO make this u16 instead of comptime_int
        alignment: comptime_int,
        address_space: AddressSpace,
        child: type,
        is_allowzero: bool,

        /// The type of the sentinel is the element type of the pointer, which is
        /// the value of the `child` field in this struct. However there is no way
        /// to refer to that type here, so we use `*const anyopaque`.
        /// See also: `sentinel`
        sentinel_ptr: ?*const anyopaque,

        /// Loads the pointer type's sentinel value from `sentinel_ptr`.
        /// Returns `null` if the pointer type has no sentinel.
        pub inline fn sentinel(comptime ptr: Pointer) ?ptr.child {
            const sp: *const ptr.child = @ptrCast(@alignCast(ptr.sentinel_ptr orelse return null));
            return sp.*;
        }

        /// This data structure is used by the Zig language code generation and
        /// therefore must be kept in sync with the compiler implementation.
        pub const Size = enum(u2) {
            one,
            many,
            slice,
            c,
        };
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Array = struct {
        len: comptime_int,
        child: type,

        /// The type of the sentinel is the element type of the array, which is
        /// the value of the `child` field in this struct. However there is no way
        /// to refer to that type here, so we use `*const anyopaque`.
        /// See also: `sentinel`.
        sentinel_ptr: ?*const anyopaque,

        /// Loads the array type's sentinel value from `sentinel_ptr`.
        /// Returns `null` if the array type has no sentinel.
        pub inline fn sentinel(comptime arr: Array) ?arr.child {
            const sp: *const arr.child = @ptrCast(@alignCast(arr.sentinel_ptr orelse return null));
            return sp.*;
        }
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const ContainerLayout = enum(u2) {
        auto,
        @"extern",
        @"packed",
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const StructField = struct {
        name: [:0]const u8,
        type: type,
        /// The type of the default value is the type of this struct field, which
        /// is the value of the `type` field in this struct. However there is no
        /// way to refer to that type here, so we use `*const anyopaque`.
        /// See also: `defaultValue`.
        default_value_ptr: ?*const anyopaque,
        is_comptime: bool,
        alignment: comptime_int,

        /// Loads the field's default value from `default_value_ptr`.
        /// Returns `null` if the field has no default value.
        pub inline fn defaultValue(comptime sf: StructField) ?sf.type {
            const dp: *const sf.type = @ptrCast(@alignCast(sf.default_value_ptr orelse return null));
            return dp.*;
        }
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Struct = struct {
        layout: ContainerLayout,
        /// Only valid if layout is .@"packed"
        backing_integer: ?type = null,
        fields: []const StructField,
        decls: []const Declaration,
        is_tuple: bool,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Optional = struct {
        child: type,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const ErrorUnion = struct {
        error_set: type,
        payload: type,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Error = struct {
        name: [:0]const u8,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const ErrorSet = ?[]const Error;

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const EnumField = struct {
        name: [:0]const u8,
        value: comptime_int,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Enum = struct {
        tag_type: type,
        fields: []const EnumField,
        decls: []const Declaration,
        is_exhaustive: bool,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const UnionField = struct {
        name: [:0]const u8,
        type: type,
        alignment: comptime_int,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Union = struct {
        layout: ContainerLayout,
        tag_type: ?type,
        fields: []const UnionField,
        decls: []const Declaration,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Fn = struct {
        calling_convention: CallingConvention,
        is_generic: bool,
        is_var_args: bool,
        /// TODO change the language spec to make this not optional.
        return_type: ?type,
        params: []const Param,

        /// This data structure is used by the Zig language code generation and
        /// therefore must be kept in sync with the compiler implementation.
        pub const Param = struct {
            is_generic: bool,
            is_noalias: bool,
            type: ?type,
        };
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Opaque = struct {
        decls: []const Declaration,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Frame = struct {
        function: *const anyopaque,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const AnyFrame = struct {
        child: ?type,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Vector = struct {
        len: comptime_int,
        child: type,
    };

    /// This data structure is used by the Zig language code generation and
    /// therefore must be kept in sync with the compiler implementation.
    pub const Declaration = struct {
        name: [:0]const u8,
    };
}