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 /*
     pybind11/attr.h: Infrastructure for processing custom
     type and function attributes
 
     Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
 
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
 */
 
 #pragma once
 
 #include "detail/common.h"
 #include "cast.h"
 #include "trampoline_self_life_support.h"
 
 #include <functional>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /// \addtogroup annotations
 /// @{
 
 /// Annotation for methods
 struct is_method {
     handle class_;
     explicit is_method(const handle &c) : class_(c) {}
 };
 
 /// Annotation for setters
 struct is_setter {};
 
 /// Annotation for operators
 struct is_operator {};
 
 /// Annotation for classes that cannot be subclassed
 struct is_final {};
 
 /// Annotation for parent scope
 struct scope {
     handle value;
     explicit scope(const handle &s) : value(s) {}
 };
 
 /// Annotation for documentation
 struct doc {
     const char *value;
     explicit doc(const char *value) : value(value) {}
 };
 
 /// Annotation for function names
 struct name {
     const char *value;
     explicit name(const char *value) : value(value) {}
 };
 
 /// Annotation indicating that a function is an overload associated with a given "sibling"
 struct sibling {
     handle value;
     explicit sibling(const handle &value) : value(value.ptr()) {}
 };
 
 /// Annotation indicating that a class derives from another given type
 template <typename T>
 struct base {
 
     PYBIND11_DEPRECATED(
         "base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
     base() = default;
 };
 
 /// Keep patient alive while nurse lives
 template <size_t Nurse, size_t Patient>
 struct keep_alive {};
 
 /// Annotation indicating that a class is involved in a multiple inheritance relationship
 struct multiple_inheritance {};
 
 /// Annotation which enables dynamic attributes, i.e. adds `__dict__` to a class
 struct dynamic_attr {};
 
 /// Annotation which enables the buffer protocol for a type
 struct buffer_protocol {};
 
 /// Annotation which enables releasing the GIL before calling the C++ destructor of wrapped
 /// instances (pybind/pybind11#1446).
 struct release_gil_before_calling_cpp_dtor {};
 
 /// Annotation which requests that a special metaclass is created for a type
 struct metaclass {
     handle value;
 
     PYBIND11_DEPRECATED("py::metaclass() is no longer required. It's turned on by default now.")
     metaclass() = default;
 
     /// Override pybind11's default metaclass
     explicit metaclass(handle value) : value(value) {}
 };
 
 /// Specifies a custom callback with signature `void (PyHeapTypeObject*)` that
 /// may be used to customize the Python type.
 ///
 /// The callback is invoked immediately before `PyType_Ready`.
 ///
 /// Note: This is an advanced interface, and uses of it may require changes to
 /// work with later versions of pybind11.  You may wish to consult the
 /// implementation of `make_new_python_type` in `detail/classes.h` to understand
 /// the context in which the callback will be run.
 struct custom_type_setup {
     using callback = std::function<void(PyHeapTypeObject *heap_type)>;
 
     explicit custom_type_setup(callback value) : value(std::move(value)) {}
 
     callback value;
 };
 
 /// Annotation that marks a class as local to the module:
 struct module_local {
     const bool value;
     constexpr explicit module_local(bool v = true) : value(v) {}
 };
 
 /// Annotation to mark enums as an arithmetic type
 struct arithmetic {};
 
 /// Mark a function for addition at the beginning of the existing overload chain instead of the end
 struct prepend {};
 
 /** \rst
     A call policy which places one or more guard variables (``Ts...``) around the function call.
 
     For example, this definition:
 
     .. code-block:: cpp
 
         m.def("foo", foo, py::call_guard<T>());
 
     is equivalent to the following pseudocode:
 
     .. code-block:: cpp
 
         m.def("foo", [](args...) {
             T scope_guard;
             return foo(args...); // forwarded arguments
         });
  \endrst */
 template <typename... Ts>
 struct call_guard;
 
 template <>
 struct call_guard<> {
     using type = detail::void_type;
 };
 
 template <typename T>
 struct call_guard<T> {
     static_assert(std::is_default_constructible<T>::value,
                   "The guard type must be default constructible");
 
     using type = T;
 };
 
 template <typename T, typename... Ts>
 struct call_guard<T, Ts...> {
     struct type {
         T guard{}; // Compose multiple guard types with left-to-right default-constructor order
         typename call_guard<Ts...>::type next{};
     };
 };
 
 /// @} annotations
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 /* Forward declarations */
 enum op_id : int;
 enum op_type : int;
 struct undefined_t;
 template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t>
 struct op_;
 void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
 
 /// Internal data structure which holds metadata about a keyword argument
 struct argument_record {
     const char *name;  ///< Argument name
     const char *descr; ///< Human-readable version of the argument value
     handle value;      ///< Associated Python object
     bool convert : 1;  ///< True if the argument is allowed to convert when loading
     bool none : 1;     ///< True if None is allowed when loading
 
     argument_record(const char *name, const char *descr, handle value, bool convert, bool none)
         : name(name), descr(descr), value(value), convert(convert), none(none) {}
 };
 
 /// Internal data structure which holds metadata about a bound function (signature, overloads,
 /// etc.)
 #define PYBIND11_DETAIL_FUNCTION_RECORD_ABI_ID "v1" // PLEASE UPDATE if the struct is changed.
 struct function_record {
     function_record()
         : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
           is_operator(false), is_method(false), is_setter(false), has_args(false),
           has_kwargs(false), prepend(false) {}
 
     /// Function name
     char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
 
     // User-specified documentation string
     char *doc = nullptr;
 
     /// Human-readable version of the function signature
     char *signature = nullptr;
 
     /// List of registered keyword arguments
     std::vector<argument_record> args;
 
     /// Pointer to lambda function which converts arguments and performs the actual call
     handle (*impl)(function_call &) = nullptr;
 
     /// Storage for the wrapped function pointer and captured data, if any
     void *data[3] = {};
 
     /// Pointer to custom destructor for 'data' (if needed)
     void (*free_data)(function_record *ptr) = nullptr;
 
     /// Return value policy associated with this function
     return_value_policy policy = return_value_policy::automatic;
 
     /// True if name == '__init__'
     bool is_constructor : 1;
 
     /// True if this is a new-style `__init__` defined in `detail/init.h`
     bool is_new_style_constructor : 1;
 
     /// True if this is a stateless function pointer
     bool is_stateless : 1;
 
     /// True if this is an operator (__add__), etc.
     bool is_operator : 1;
 
     /// True if this is a method
     bool is_method : 1;
 
     /// True if this is a setter
     bool is_setter : 1;
 
     /// True if the function has a '*args' argument
     bool has_args : 1;
 
     /// True if the function has a '**kwargs' argument
     bool has_kwargs : 1;
 
     /// True if this function is to be inserted at the beginning of the overload resolution chain
     bool prepend : 1;
 
     /// Number of arguments (including py::args and/or py::kwargs, if present)
     std::uint16_t nargs;
 
     /// Number of leading positional arguments, which are terminated by a py::args or py::kwargs
     /// argument or by a py::kw_only annotation.
     std::uint16_t nargs_pos = 0;
 
     /// Number of leading arguments (counted in `nargs`) that are positional-only
     std::uint16_t nargs_pos_only = 0;
 
     /// Python method object
     PyMethodDef *def = nullptr;
 
     /// Python handle to the parent scope (a class or a module)
     handle scope;
 
     /// Python handle to the sibling function representing an overload chain
     handle sibling;
 
     /// Pointer to next overload
     function_record *next = nullptr;
 };
 // The main purpose of this macro is to make it easy to pin-point the critically related code
 // sections.
 #define PYBIND11_ENSURE_PRECONDITION_FOR_FUNCTIONAL_H_PERFORMANCE_OPTIMIZATIONS(...)              \
     static_assert(                                                                                \
         __VA_ARGS__,                                                                              \
         "Violation of precondition for pybind11/functional.h performance optimizations!")
 
 /// Special data structure which (temporarily) holds metadata about a bound class
 struct type_record {
     PYBIND11_NOINLINE type_record()
         : multiple_inheritance(false), dynamic_attr(false), buffer_protocol(false),
           module_local(false), is_final(false), release_gil_before_calling_cpp_dtor(false) {}
 
     /// Handle to the parent scope
     handle scope;
 
     /// Name of the class
     const char *name = nullptr;
 
     // Pointer to RTTI type_info data structure
     const std::type_info *type = nullptr;
 
     /// How large is the underlying C++ type?
     size_t type_size = 0;
 
     /// What is the alignment of the underlying C++ type?
     size_t type_align = 0;
 
     /// How large is the type's holder?
     size_t holder_size = 0;
 
     /// The global operator new can be overridden with a class-specific variant
     void *(*operator_new)(size_t) = nullptr;
 
     /// Function pointer to class_<..>::init_instance
     void (*init_instance)(instance *, const void *) = nullptr;
 
     /// Function pointer to class_<..>::dealloc
     void (*dealloc)(detail::value_and_holder &) = nullptr;
 
     /// Function pointer for casting alias class (aka trampoline) pointer to
     /// trampoline_self_life_support pointer. Sidesteps cross-DSO RTTI issues
     /// on platforms like macOS (see PR #5728 for details).
     get_trampoline_self_life_support_fn get_trampoline_self_life_support
         = [](void *) -> trampoline_self_life_support * { return nullptr; };
 
     /// List of base classes of the newly created type
     list bases;
 
     /// Optional docstring
     const char *doc = nullptr;
 
     /// Custom metaclass (optional)
     handle metaclass;
 
     /// Custom type setup.
     custom_type_setup::callback custom_type_setup_callback;
 
     /// Multiple inheritance marker
     bool multiple_inheritance : 1;
 
     /// Does the class manage a __dict__?
     bool dynamic_attr : 1;
 
     /// Does the class implement the buffer protocol?
     bool buffer_protocol : 1;
 
     /// Is the class definition local to the module shared object?
     bool module_local : 1;
 
     /// Is the class inheritable from python classes?
     bool is_final : 1;
 
     /// Solves pybind/pybind11#1446
     bool release_gil_before_calling_cpp_dtor : 1;
 
     holder_enum_t holder_enum_v = holder_enum_t::undefined;
 
     PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *) ) {
         auto *base_info = detail::get_type_info(base, false);
         if (!base_info) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
             pybind11_fail("generic_type: type \"" + std::string(name)
                           + "\" referenced unknown base type \"" + tname + "\"");
         }
 
         // SMART_HOLDER_BAKEIN_FOLLOW_ON: Refine holder compatibility checks.
         bool this_has_unique_ptr_holder = (holder_enum_v == holder_enum_t::std_unique_ptr);
         bool base_has_unique_ptr_holder
             = (base_info->holder_enum_v == holder_enum_t::std_unique_ptr);
         if (this_has_unique_ptr_holder != base_has_unique_ptr_holder) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
             pybind11_fail("generic_type: type \"" + std::string(name) + "\" "
                           + (this_has_unique_ptr_holder ? "does not have" : "has")
                           + " a non-default holder type while its base \"" + tname + "\" "
                           + (base_has_unique_ptr_holder ? "does not" : "does"));
         }
 
         bases.append(reinterpret_cast<PyObject *>(base_info->type));
 
 #ifdef PYBIND11_BACKWARD_COMPATIBILITY_TP_DICTOFFSET
         dynamic_attr |= base_info->type->tp_dictoffset != 0;
 #else
         dynamic_attr |= (base_info->type->tp_flags & Py_TPFLAGS_MANAGED_DICT) != 0;
 #endif
 
         if (caster) {
             base_info->implicit_casts.emplace_back(type, caster);
         }
     }
 };
 
 inline function_call::function_call(const function_record &f, handle p) : func(f), parent(p) {
     args.reserve(f.nargs);
     args_convert.reserve(f.nargs);
 }
 
 /// Tag for a new-style `__init__` defined in `detail/init.h`
 struct is_new_style_constructor {};
 
 /**
  * Partial template specializations to process custom attributes provided to
  * cpp_function_ and class_. These are either used to initialize the respective
  * fields in the type_record and function_record data structures or executed at
  * runtime to deal with custom call policies (e.g. keep_alive).
  */
 template <typename T, typename SFINAE = void>
 struct process_attribute;
 
 template <typename T>
 struct process_attribute_default {
     /// Default implementation: do nothing
     static void init(const T &, function_record *) {}
     static void init(const T &, type_record *) {}
     static void precall(function_call &) {}
     static void postcall(function_call &, handle) {}
 };
 
 /// Process an attribute specifying the function's name
 template <>
 struct process_attribute<name> : process_attribute_default<name> {
     static void init(const name &n, function_record *r) { r->name = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring
 template <>
 struct process_attribute<doc> : process_attribute_default<doc> {
     static void init(const doc &n, function_record *r) { r->doc = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring (provided as a C-style string)
 template <>
 struct process_attribute<const char *> : process_attribute_default<const char *> {
     static void init(const char *d, function_record *r) { r->doc = const_cast<char *>(d); }
     static void init(const char *d, type_record *r) { r->doc = d; }
 };
 template <>
 struct process_attribute<char *> : process_attribute<const char *> {};
 
 /// Process an attribute indicating the function's return value policy
 template <>
 struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
     static void init(const return_value_policy &p, function_record *r) { r->policy = p; }
 };
 
 /// Process an attribute which indicates that this is an overloaded function associated with a
 /// given sibling
 template <>
 struct process_attribute<sibling> : process_attribute_default<sibling> {
     static void init(const sibling &s, function_record *r) { r->sibling = s.value; }
 };
 
 /// Process an attribute which indicates that this function is a method
 template <>
 struct process_attribute<is_method> : process_attribute_default<is_method> {
     static void init(const is_method &s, function_record *r) {
         r->is_method = true;
         r->scope = s.class_;
     }
 };
 
 /// Process an attribute which indicates that this function is a setter
 template <>
 struct process_attribute<is_setter> : process_attribute_default<is_setter> {
     static void init(const is_setter &, function_record *r) { r->is_setter = true; }
 };
 
 /// Process an attribute which indicates the parent scope of a method
 template <>
 struct process_attribute<scope> : process_attribute_default<scope> {
     static void init(const scope &s, function_record *r) { r->scope = s.value; }
 };
 
 /// Process an attribute which indicates that this function is an operator
 template <>
 struct process_attribute<is_operator> : process_attribute_default<is_operator> {
     static void init(const is_operator &, function_record *r) { r->is_operator = true; }
 };
 
 template <>
 struct process_attribute<is_new_style_constructor>
     : process_attribute_default<is_new_style_constructor> {
     static void init(const is_new_style_constructor &, function_record *r) {
         r->is_new_style_constructor = true;
     }
 };
 
 inline void check_kw_only_arg(const arg &a, function_record *r) {
     if (r->args.size() > r->nargs_pos && (!a.name || a.name[0] == '\0')) {
         pybind11_fail("arg(): cannot specify an unnamed argument after a kw_only() annotation or "
                       "args() argument");
     }
 }
 
 inline void append_self_arg_if_needed(function_record *r) {
     if (r->is_method && r->args.empty()) {
         r->args.emplace_back("self", nullptr, handle(), /*convert=*/true, /*none=*/false);
     }
 }
 
 /// Process a keyword argument attribute (*without* a default value)
 template <>
 struct process_attribute<arg> : process_attribute_default<arg> {
     static void init(const arg &a, function_record *r) {
         append_self_arg_if_needed(r);
         r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
 
         check_kw_only_arg(a, r);
     }
 };
 
 /// Process a keyword argument attribute (*with* a default value)
 template <>
 struct process_attribute<arg_v> : process_attribute_default<arg_v> {
     static void init(const arg_v &a, function_record *r) {
         if (r->is_method && r->args.empty()) {
             r->args.emplace_back(
                 "self", /*descr=*/nullptr, /*parent=*/handle(), /*convert=*/true, /*none=*/false);
         }
 
         if (!a.value) {
 #if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             std::string descr("'");
             if (a.name) {
                 descr += std::string(a.name) + ": ";
             }
             descr += a.type + "'";
             if (r->is_method) {
                 if (r->name) {
                     descr += " in method '" + (std::string) str(r->scope) + "."
                              + (std::string) r->name + "'";
                 } else {
                     descr += " in method of '" + (std::string) str(r->scope) + "'";
                 }
             } else if (r->name) {
                 descr += " in function '" + (std::string) r->name + "'";
             }
             pybind11_fail("arg(): could not convert default argument " + descr
                           + " into a Python object (type not registered yet?)");
 #else
             pybind11_fail("arg(): could not convert default argument "
                           "into a Python object (type not registered yet?). "
                           "#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for "
                           "more information.");
 #endif
         }
         r->args.emplace_back(a.name, a.descr, a.value.inc_ref(), !a.flag_noconvert, a.flag_none);
 
         check_kw_only_arg(a, r);
     }
 };
 
 /// Process a keyword-only-arguments-follow pseudo argument
 template <>
 struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
         append_self_arg_if_needed(r);
         if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size())) {
             pybind11_fail("Mismatched args() and kw_only(): they must occur at the same relative "
                           "argument location (or omit kw_only() entirely)");
         }
         r->nargs_pos = static_cast<std::uint16_t>(r->args.size());
     }
 };
 
 /// Process a positional-only-argument maker
 template <>
 struct process_attribute<pos_only> : process_attribute_default<pos_only> {
     static void init(const pos_only &, function_record *r) {
         append_self_arg_if_needed(r);
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
         if (r->nargs_pos_only > r->nargs_pos) {
             pybind11_fail("pos_only(): cannot follow a py::args() argument");
         }
         // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
     }
 };
 
 /// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees
 /// that)
 template <typename T>
 struct process_attribute<T, enable_if_t<is_pyobject<T>::value>>
     : process_attribute_default<handle> {
     static void init(const handle &h, type_record *r) { r->bases.append(h); }
 };
 
 /// Process a parent class attribute (deprecated, does not support multiple inheritance)
 template <typename T>
 struct process_attribute<base<T>> : process_attribute_default<base<T>> {
     static void init(const base<T> &, type_record *r) { r->add_base(typeid(T), nullptr); }
 };
 
 /// Process a multiple inheritance attribute
 template <>
 struct process_attribute<multiple_inheritance> : process_attribute_default<multiple_inheritance> {
     static void init(const multiple_inheritance &, type_record *r) {
         r->multiple_inheritance = true;
     }
 };
 
 template <>
 struct process_attribute<dynamic_attr> : process_attribute_default<dynamic_attr> {
     static void init(const dynamic_attr &, type_record *r) { r->dynamic_attr = true; }
 };
 
 template <>
 struct process_attribute<custom_type_setup> {
     static void init(const custom_type_setup &value, type_record *r) {
         r->custom_type_setup_callback = value.value;
     }
 };
 
 template <>
 struct process_attribute<is_final> : process_attribute_default<is_final> {
     static void init(const is_final &, type_record *r) { r->is_final = true; }
 };
 
 template <>
 struct process_attribute<buffer_protocol> : process_attribute_default<buffer_protocol> {
     static void init(const buffer_protocol &, type_record *r) { r->buffer_protocol = true; }
 };
 
 template <>
 struct process_attribute<metaclass> : process_attribute_default<metaclass> {
     static void init(const metaclass &m, type_record *r) { r->metaclass = m.value; }
 };
 
 template <>
 struct process_attribute<module_local> : process_attribute_default<module_local> {
     static void init(const module_local &l, type_record *r) { r->module_local = l.value; }
 };
 
 template <>
 struct process_attribute<release_gil_before_calling_cpp_dtor>
     : process_attribute_default<release_gil_before_calling_cpp_dtor> {
     static void init(const release_gil_before_calling_cpp_dtor &, type_record *r) {
         r->release_gil_before_calling_cpp_dtor = true;
     }
 };
 
 /// Process a 'prepend' attribute, putting this at the beginning of the overload chain
 template <>
 struct process_attribute<prepend> : process_attribute_default<prepend> {
     static void init(const prepend &, function_record *r) { r->prepend = true; }
 };
 
 /// Process an 'arithmetic' attribute for enums (does nothing here)
 template <>
 struct process_attribute<arithmetic> : process_attribute_default<arithmetic> {};
 
 template <typename... Ts>
 struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> {};
 
 /**
  * Process a keep_alive call policy -- invokes keep_alive_impl during the
  * pre-call handler if both Nurse, Patient != 0 and use the post-call handler
  * otherwise
  */
 template <size_t Nurse, size_t Patient>
 struct process_attribute<keep_alive<Nurse, Patient>>
     : public process_attribute_default<keep_alive<Nurse, Patient>> {
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
     static void precall(function_call &call) {
         keep_alive_impl(Nurse, Patient, call, handle());
     }
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
     static void postcall(function_call &, handle) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
     static void precall(function_call &) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
     static void postcall(function_call &call, handle ret) {
         keep_alive_impl(Nurse, Patient, call, ret);
     }
 };
 
 /// Recursively iterate over variadic template arguments
 template <typename... Args>
 struct process_attributes {
     static void init(const Args &...args, function_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
         (void) expander{
             0, ((void) process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
     static void init(const Args &...args, type_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
         (void) expander{0,
                         (process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
     static void precall(function_call &call) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call);
         using expander = int[];
         (void) expander{0,
                         (process_attribute<typename std::decay<Args>::type>::precall(call), 0)...};
     }
     static void postcall(function_call &call, handle fn_ret) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call, fn_ret);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(fn_ret);
         using expander = int[];
         (void) expander{
             0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0)...};
     }
 };
 
 template <typename T>
 struct is_keep_alive : std::false_type {};
 
 template <size_t Nurse, size_t Patient>
 struct is_keep_alive<keep_alive<Nurse, Patient>> : std::true_type {};
 
 template <typename T>
 using is_call_guard = is_instantiation<call_guard, T>;
 
 /// Extract the ``type`` from the first `call_guard` in `Extras...` (or `void_type` if none found)
 template <typename... Extra>
 using extract_guard_t = typename exactly_one_t<is_call_guard, call_guard<>, Extra...>::type;
 
 /// Check the number of named arguments at compile time
 template <typename... Extra,
           size_t named = constexpr_sum(std::is_base_of<arg, Extra>::value...),
           size_t self = constexpr_sum(std::is_same<is_method, Extra>::value...)>
 constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(nargs, has_args, has_kwargs);
     return named == 0
            || (self + named + static_cast<size_t>(has_args) + static_cast<size_t>(has_kwargs))
                   == nargs;
 }
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

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