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1777 lines (1551 loc) · 65.6 KB
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// Copyright (c) Herb Sutter
// SPDX-License-Identifier: CC-BY-NC-ND-4.0
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//===========================================================================
// Cpp2 utilities:
// Language support implementations
// #include'd by generated Cpp1 code
//===========================================================================
#ifndef __CPP2_UTIL
#define __CPP2_UTIL
// If this implementation doesn't support source_location yet, disable it
// TODO: technically this test should have <version> included first, but GEFN
#if !defined(_MSC_VER) && !defined(__cpp_lib_source_location)
#undef CPP2_USE_SOURCE_LOCATION
#endif
// If the cppfront user requested -pure-cpp2, this will be set
// and we should be using modules only
#ifdef CPP2_USE_MODULES
// If we have real modules, use those the best we can
// as implementations are still underway
#ifdef __cpp_modules
#ifndef _MSC_VER
// This is the ideal -- note that we just voted "import std;"
// into draft C++23 in late July 2022, so implementers haven't
// had time to catch up yet. As of this writing (September 2022)
// no compiler will take this path yet, but they're on the way...
import std;
#else // MSVC
// Note: When C++23 "import std;" is available, we will switch to that here
// In the meantime, this is what works on MSVC which is the only compiler
// I've been able to get access to that implements modules enough to demo
// (but we'll have more full-C++20 compilers soon!)
import std.core;
import std.regex;
import std.filesystem;
import std.memory;
import std.threading;
// Suppress spurious MSVC modules warning
#pragma warning(disable:5050)
#endif
// Otherwise, "fake it till you make it"... include (nearly) all the
// standard headers, with a feature test #ifdef for each header that
// isn't yet supported by all of { VS 2022, g++-10, clang++-12 }
// ... this should approximate "import std;" on those compilers
#else
#include <version>
#include <concepts>
#ifdef __cpp_lib_coroutine
#include <coroutine>
#endif
#include <any>
#include <bitset>
#include <chrono>
#include <compare>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdlib>
#include <ctime>
#include <functional>
#include <initializer_list>
#include <optional>
#ifdef __cpp_lib_source_location
#include <source_location>
#endif
#include <tuple>
#include <type_traits>
#include <typeindex>
#ifndef CPP2_NO_RTTI
#include <typeinfo>
#endif
#include <utility>
#include <variant>
#include <memory>
#ifdef __cpp_lib_memory_resource
#include <memory_resource>
#endif
#include <new>
#include <scoped_allocator>
#include <cfloat>
#include <cinttypes>
#include <climits>
#include <cstdint>
#include <limits>
#include <cassert>
#include <cerrno>
#ifndef CPP2_NO_EXCEPTIONS
#include <exception>
#endif
#include <stdexcept>
#include <system_error>
#include <cctype>
#include <charconv>
#include <cstring>
#if __has_include(<cuchar>)
#include <cuchar>
#endif
#include <cwchar>
#include <cwctype>
#ifdef __cpp_lib_format
#include <format>
#endif
#include <string>
#include <string_view>
#include <array>
#include <deque>
#include <forward_list>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <span>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <iterator>
#include <ranges>
#include <algorithm>
#include <bit>
#include <cfenv>
#include <cmath>
#include <complex>
#include <numbers>
#include <numeric>
#include <random>
#include <ratio>
#include <valarray>
#include <clocale>
#include <codecvt>
#include <locale>
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#ifdef __cpp_lib_spanstream
#include <spanstream>
#endif
#include <sstream>
#include <streambuf>
#ifdef __cpp_lib_syncstream
#include <syncstream>
#endif
#include <filesystem>
#include <regex>
#include <atomic>
#ifdef __cpp_lib_barrier
#include <barrier>
#endif
#include <condition_variable>
#include <future>
#ifdef __cpp_lib_latch
#include <latch>
#endif
#include <mutex>
#ifdef __cpp_lib_semaphore
#include <semaphore>
#endif
#include <shared_mutex>
#ifdef __cpp_lib_jthread
#include <stop_token>
#endif
#include <thread>
#include <iso646.h>
// libstdc++ currently has a dependency on linking TBB if <execution> is
// included, and TBB seems to be not automatically installed and linkable
// on some GCC installations, so let's not pull in that little-used header
// in our -pure-cpp2 "import std;" simulation mode... if you need this,
// use mixed mode (not -pure-cpp2) and #include all the headers you need
// including this one
//
// #include <execution>
#endif
// Otherwise, we're not in -pure-cpp2 and so just #include
// what we need in this header to make this self-contained
#else
#include <type_traits>
#include <new>
#include <memory>
#include <tuple>
#include <string>
#include <string_view>
#include <vector>
#include <iostream>
#include <variant>
#include <any>
#include <optional>
#include <cstddef>
#include <utility>
#include <cstdio>
#include <cstdint>
#include <algorithm>
#include <compare>
#include <iterator>
#include <concepts>
#include <system_error>
#ifndef CPP2_NO_EXCEPTIONS
#include <exception>
#endif
#ifndef CPP2_NO_RTTI
#include <typeinfo>
#endif
#if defined(CPP2_USE_SOURCE_LOCATION)
#include <source_location>
#endif
#endif
#define CPP2_TYPEOF(x) std::remove_cvref_t<decltype(x)>
#define CPP2_FORWARD(x) std::forward<decltype(x)>(x)
#define CPP2_CONTINUE_BREAK(NAME) goto CONTINUE_##NAME; CONTINUE_##NAME: continue; goto BREAK_##NAME; BREAK_##NAME: break;
// these redundant goto's to avoid 'unused label' warnings
namespace cpp2 {
//-----------------------------------------------------------------------
//
// Convenience names for fundamental types
//
// Note: De jure, some of these are optional per the C and C++ standards
// De facto, all of these are supported in all implementations I know of
//
//-----------------------------------------------------------------------
//
// Encouraged by default: Fixed-precision names
using i8 = std::int8_t ;
using i16 = std::int16_t ;
using i32 = std::int32_t ;
using i64 = std::int64_t ;
using u8 = std::uint8_t ;
using u16 = std::uint16_t ;
using u32 = std::uint32_t ;
using u64 = std::uint64_t ;
// Discouraged: Variable precision names
// short
using ushort = unsigned short;
// int
using ulong = unsigned long;
// long
using longlong = long long;
using ulonglong = unsigned long long;
using longdouble = long double;
// Strongly discouraged, for compatibility/interop only
using __schar = signed char; // normally use i8 instead
using __uchar = unsigned char; // normally use u8 instead
//-----------------------------------------------------------------------
//
// String: A helper workaround for passing a string literal as a
// template argument
//
//-----------------------------------------------------------------------
//
template<size_t N>
struct String
{
constexpr String(const char (&str)[N])
{
std::copy_n(str, N, value);
}
auto operator<=>(String const&) const = default;
char value[N] = {};
};
//-----------------------------------------------------------------------
//
// contract_group
//
//-----------------------------------------------------------------------
//
#ifdef CPP2_USE_SOURCE_LOCATION
#define CPP2_SOURCE_LOCATION_PARAM , std::source_location where
#define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT , std::source_location where = std::source_location::current()
#define CPP2_SOURCE_LOCATION_PARAM_SOLO std::source_location where
#define CPP2_SOURCE_LOCATION_ARG , where
#else
#define CPP2_SOURCE_LOCATION_PARAM
#define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT
#define CPP2_SOURCE_LOCATION_PARAM_SOLO
#define CPP2_SOURCE_LOCATION_ARG
#endif
// For C++23: make this std::string_view and drop the macro
// Before C++23 std::string_view was not guaranteed to be trivially copyable,
// and so in<T> will pass it by const& and really it should be by value
#define CPP2_MESSAGE_PARAM char const*
class contract_group {
public:
using handler = void (*)(CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM);
constexpr contract_group (handler h = {}) : reporter(h) { }
constexpr auto set_handler(handler h);
constexpr auto get_handler() const -> handler { return reporter; }
constexpr auto expects (bool b, CPP2_MESSAGE_PARAM msg = "" CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT)
-> void { if (!b) reporter(msg CPP2_SOURCE_LOCATION_ARG); }
private:
handler reporter;
};
[[noreturn]] inline auto report_and_terminate(std::string_view group, CPP2_MESSAGE_PARAM msg = "" CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) noexcept -> void {
std::cerr
#ifdef CPP2_USE_SOURCE_LOCATION
<< where.file_name() << "("
<< where.line() << ") "
<< where.function_name() << ": "
#endif
<< group << " violation";
if (msg[0] != '\0') {
std::cerr << ": " << msg;
}
std::cerr << "\n";
std::terminate();
}
auto inline Default = contract_group(
[](CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM)noexcept {
report_and_terminate("Contract", msg CPP2_SOURCE_LOCATION_ARG);
}
);
auto inline Bounds = contract_group(
[](CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM)noexcept {
report_and_terminate("Bounds safety", msg CPP2_SOURCE_LOCATION_ARG);
}
);
auto inline Null = contract_group(
[](CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM)noexcept {
report_and_terminate("Null safety", msg CPP2_SOURCE_LOCATION_ARG);
}
);
auto inline Type = contract_group(
[](CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM)noexcept {
report_and_terminate("Type safety", msg CPP2_SOURCE_LOCATION_ARG);
}
);
auto inline Testing = contract_group(
[](CPP2_MESSAGE_PARAM msg CPP2_SOURCE_LOCATION_PARAM)noexcept {
report_and_terminate("Testing", msg CPP2_SOURCE_LOCATION_ARG);
}
);
constexpr auto contract_group::set_handler(handler h) {
Default.expects(h);
reporter = h;
}
// Null pointer deref checking
//
auto assert_not_null(auto&& p CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
{
// NOTE: This "!= T{}" test may or may not work for STL iterators. The standard
// doesn't guarantee that using == and != will reliably report whether an
// STL iterator has the default-constructed value. So use it only for raw *...
if constexpr (std::is_pointer_v<CPP2_TYPEOF(p)>) {
Null.expects(p != CPP2_TYPEOF(p){}, "dynamic null dereference attempt detected" CPP2_SOURCE_LOCATION_ARG);
}
return CPP2_FORWARD(p);
}
// Subscript bounds checking
//
auto assert_in_bounds(auto&& x, auto&& arg CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
requires (std::is_integral_v<CPP2_TYPEOF(arg)> &&
requires { std::ssize(x); x[arg]; std::begin(x) + 2; })
{
Bounds.expects(0 <= arg && arg < std::ssize(x), "out of bounds access attempt detected" CPP2_SOURCE_LOCATION_ARG);
return CPP2_FORWARD(x) [ CPP2_FORWARD(arg) ];
}
auto assert_in_bounds(auto&& x, auto&& arg CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
requires (!(std::is_integral_v<CPP2_TYPEOF(arg)> &&
requires { std::ssize(x); x[arg]; std::begin(x) + 2; }))
{
return CPP2_FORWARD(x) [ CPP2_FORWARD(arg) ];
}
//-----------------------------------------------------------------------
//
// Support wrappers that unblock using this file in environments that
// disable EH or RTTI
//
// Note: This is not endorsing disabling those features, it's just
// recognizing that disabling them is popular (e.g., games, WASM)
// and so we should remove a potential adoption blocker... only a
// few features in this file depend on EH or RTTI anyway, and
// wouldn't be exercised in such an environment anyway so there
// is no real net loss here
//
//-----------------------------------------------------------------------
//
[[noreturn]] auto Throw(auto&& x, [[maybe_unused]] char const* msg) -> void {
#ifdef CPP2_NO_EXCEPTIONS
Type.expects(
!"exceptions are disabled with -fno-exceptions",
msg
);
std::terminate();
#else
throw CPP2_FORWARD(x);
#endif
}
inline auto Uncaught_exceptions() -> int {
#ifdef CPP2_NO_EXCEPTIONS
return 0;
#else
return std::uncaught_exceptions();
#endif
}
template<typename T>
auto Dynamic_cast( [[maybe_unused]] auto&& x ) -> decltype(auto) {
#ifdef CPP2_NO_RTTI
Type.expects(
!"'as' dynamic casting is disabled with -fno-rtti", // more likely to appear on console
"'as' dynamic casting is disabled with -fno-rtti" // make message available to hooked handlers
);
return nullptr;
#else
return dynamic_cast<T>(CPP2_FORWARD(x));
#endif
}
template<typename T>
auto Typeid() -> decltype(auto) {
#ifdef CPP2_NO_RTTI
Type.expects(
!"'any' dynamic casting is disabled with -fno-rtti", // more likely to appear on console
"'any' dynamic casting is disabled with -fno-rtti" // make message available to hooked handlers
);
#else
return typeid(T);
#endif
}
// We don't need typeid(expr) yet -- uncomment this if/when we need it
//auto Typeid( [[maybe_unused]] auto&& x ) -> decltype(auto) {
//#ifdef CPP2_NO_RTTI
// Type.expects(
// !"<write appropriate error message here>"
// );
//#else
// return typeid(CPP2_FORWARD(x));
//#endif
//}
//-----------------------------------------------------------------------
//
// Arena objects for std::allocators
//
// Note: cppfront translates "new" to "cpp2_new", so in Cpp2 code
// these are invoked by simply "unique.new<T>" etc.
//
//-----------------------------------------------------------------------
//
struct {
template<typename T>
[[nodiscard]] auto cpp2_new(auto&& ...args) const -> std::unique_ptr<T> {
return std::make_unique<T>(CPP2_FORWARD(args)...);
}
} unique;
[[maybe_unused]] struct {
template<typename T>
[[nodiscard]] auto cpp2_new(auto&& ...args) const -> std::shared_ptr<T> {
return std::make_shared<T>(CPP2_FORWARD(args)...);
}
} shared;
template<typename T>
[[nodiscard]] auto cpp2_new(auto&& ...args) -> std::unique_ptr<T> {
return unique.cpp2_new<T>(CPP2_FORWARD(args)...);
}
//-----------------------------------------------------------------------
//
// in<T> For "in" parameter
//
//-----------------------------------------------------------------------
//
template<typename T>
constexpr bool prefer_pass_by_value =
sizeof(T) <= 2*sizeof(void*)
&& std::is_trivially_copy_constructible_v<T>;
template<typename T>
requires std::is_class_v<T> || std::is_union_v<T> || std::is_array_v<T> || std::is_function_v<T>
constexpr bool prefer_pass_by_value<T> = false;
template<typename T>
requires (!std::is_void_v<T>)
using in =
std::conditional_t <
prefer_pass_by_value<T>,
T const,
T const&
>;
//-----------------------------------------------------------------------
//
// Initialization: These are closely related...
//
// deferred_init<T> For deferred-initialized local object
//
// out<T> For out parameter
//
//-----------------------------------------------------------------------
//
template<typename T>
class deferred_init {
bool init = false;
alignas(T) std::byte data[sizeof(T)]; // or: std::aligned_storage_t<sizeof(T), alignof(T)> data
auto t() -> T& { return *std::launder(reinterpret_cast<T*>(&data)); }
template<typename U>
friend class out;
auto destroy() -> void { if (init) { t().~T(); } init = false; }
public:
deferred_init() noexcept { }
~deferred_init() noexcept { destroy(); }
auto value() noexcept -> T& { Default.expects(init); return t(); }
auto construct (auto&& ...args) -> void { Default.expects(!init); new (&data) T(CPP2_FORWARD(args)...); init = true; }
auto construct_list(auto&& ...args) -> void { Default.expects(!init); new (&data) T{CPP2_FORWARD(args)...}; init = true; }
};
template<typename T>
class out {
// Not going to bother with std::variant here
union {
T* t;
deferred_init<T>* dt;
};
out<T>* ot = {};
bool has_t;
// Each out in a chain contains its own uncaught_count ...
int uncaught_count = Uncaught_exceptions();
// ... but all in a chain share the topmost called_construct_
bool called_construct_ = false;
public:
out(T* t_) noexcept : t{ t_}, has_t{true} { Default.expects( t); }
out(deferred_init<T>* dt_) noexcept : dt{dt_}, has_t{false} { Default.expects(dt); }
out(out<T>* ot_) noexcept : ot{ot_}, has_t{ot_->has_t} { Default.expects(ot);
if (has_t) { t = ot->t; }
else { dt = ot->dt; }
}
auto called_construct() -> bool& {
if (ot) { return ot->called_construct(); }
else { return called_construct_; }
}
// In the case of an exception, if the parameter was uninitialized
// then leave it in the same state on exit (strong guarantee)
~out() {
if (called_construct() && uncaught_count != Uncaught_exceptions()) {
Default.expects(!has_t);
dt->destroy();
called_construct() = false;
}
}
auto construct(auto&& ...args) -> void {
if (has_t || called_construct()) {
if constexpr (requires { *t = T(CPP2_FORWARD(args)...); }) {
Default.expects( t );
*t = T(CPP2_FORWARD(args)...);
}
else {
Default.expects(!"attempted to copy assign, but copy assignment is not available");
}
}
else {
Default.expects( dt );
if (dt->init) {
if constexpr (requires { *t = T(CPP2_FORWARD(args)...); }) {
dt->value() = T(CPP2_FORWARD(args)...);
}
else {
Default.expects(!"attempted to copy assign, but copy assignment is not available");
}
}
else {
dt->construct(CPP2_FORWARD(args)...);
called_construct() = true;
}
}
}
auto construct_list(auto&& ...args) -> void {
if (has_t || called_construct()) {
if constexpr (requires { *t = T{CPP2_FORWARD(args)...}; }) {
Default.expects( t );
*t = T{CPP2_FORWARD(args)...};
}
else {
Default.expects(!"attempted to copy assign, but copy assignment is not available");
}
}
else {
Default.expects( dt );
if (dt->init) {
if constexpr (requires { *t = T{CPP2_FORWARD(args)...}; }) {
dt->value() = T{CPP2_FORWARD(args)...};
}
else {
Default.expects(!"attempted to copy assign, but copy assignment is not available");
}
}
else {
dt->construct(CPP2_FORWARD(args)...);
called_construct() = true;
}
}
}
auto value() noexcept -> T& {
if (has_t) {
Default.expects( t );
return *t;
}
else {
Default.expects( dt );
return dt->value();
}
}
};
//-----------------------------------------------------------------------
//
// CPP2_UFCS: Variadic macro generating a variadic lamba, oh my...
//
//-----------------------------------------------------------------------
//
#if defined(_MSC_VER) && !defined(__clang_major__)
#define CPP2_FORCE_INLINE __forceinline
#define CPP2_FORCE_INLINE_LAMBDA [[msvc::forceinline]]
#define CPP2_LAMBDA_NO_DISCARD
#else
#define CPP2_FORCE_INLINE __attribute__((always_inline))
#define CPP2_FORCE_INLINE_LAMBDA __attribute__((always_inline))
#if defined(__clang_major__)
// Also check __cplusplus, only to satisfy Clang -pedantic-errors
#if __cplusplus >= 202302L && (__clang_major__ > 13 || (__clang_major__ == 13 && __clang_minor__ >= 2))
#define CPP2_LAMBDA_NO_DISCARD [[nodiscard]]
#else
#define CPP2_LAMBDA_NO_DISCARD
#endif
#elif defined(__GNUC__)
#if __GNUC__ >= 9
#define CPP2_LAMBDA_NO_DISCARD [[nodiscard]]
#else
#define CPP2_LAMBDA_NO_DISCARD
#endif
#else
#define CPP2_LAMBDA_NO_DISCARD
#endif
#endif
// Note: [&] is because a nested UFCS might be viewed as trying to capture 'this'
#define CPP2_UFCS(FUNCNAME,PARAM1,...) \
[&] CPP2_LAMBDA_NO_DISCARD (auto&& obj, auto&& ...params) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).FUNCNAME(CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).FUNCNAME(CPP2_FORWARD(params)...); \
} else { \
return FUNCNAME(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
}(PARAM1, __VA_ARGS__)
#define CPP2_UFCS_0(FUNCNAME,PARAM1) \
[&] CPP2_LAMBDA_NO_DISCARD (auto&& obj) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).FUNCNAME(); }) { \
return CPP2_FORWARD(obj).FUNCNAME(); \
} else { \
return FUNCNAME(CPP2_FORWARD(obj)); \
} \
}(PARAM1)
#define CPP2_UFCS_REMPARENS(...) __VA_ARGS__
#define CPP2_UFCS_TEMPLATE(FUNCNAME,TEMPARGS,PARAM1,...) \
[&] CPP2_LAMBDA_NO_DISCARD (auto&& obj, auto&& ...params) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(params)...); \
} else { \
return FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
}(PARAM1, __VA_ARGS__)
#define CPP2_UFCS_TEMPLATE_0(FUNCNAME,TEMPARGS,PARAM1) \
[&] CPP2_LAMBDA_NO_DISCARD (auto&& obj) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (); }) { \
return CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (); \
} else { \
return FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(obj)); \
} \
}(PARAM1)
// But for non-local lambdas [&] is not allowed
#define CPP2_UFCS_NONLOCAL(FUNCNAME,PARAM1,...) \
[] CPP2_LAMBDA_NO_DISCARD (auto&& obj, auto&& ...params) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).FUNCNAME(CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).FUNCNAME(CPP2_FORWARD(params)...); \
} else { \
return FUNCNAME(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
}(PARAM1, __VA_ARGS__)
#define CPP2_UFCS_0_NONLOCAL(FUNCNAME,PARAM1) \
[] CPP2_LAMBDA_NO_DISCARD (auto&& obj) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).FUNCNAME(); }) { \
return CPP2_FORWARD(obj).FUNCNAME(); \
} else { \
return FUNCNAME(CPP2_FORWARD(obj)); \
} \
}(PARAM1)
#define CPP2_UFCS_TEMPLATE_NONLOCAL(FUNCNAME,TEMPARGS,PARAM1,...) \
[] CPP2_LAMBDA_NO_DISCARD (auto&& obj, auto&& ...params) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(params)...); \
} else { \
return FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
}(PARAM1, __VA_ARGS__)
#define CPP2_UFCS_TEMPLATE_0_NONLOCAL(FUNCNAME,TEMPARGS,PARAM1) \
[] CPP2_LAMBDA_NO_DISCARD (auto&& obj) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) { \
if constexpr (requires{ CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (); }) { \
return CPP2_FORWARD(obj).template FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (); \
} else { \
return FUNCNAME CPP2_UFCS_REMPARENS TEMPARGS (CPP2_FORWARD(obj)); \
} \
}(PARAM1)
//-----------------------------------------------------------------------
//
// is and as
//
//-----------------------------------------------------------------------
//
//-------------------------------------------------------------------------------------------------------------
// Built-in is
//
// For designating "holds no value" -- used only with is, not as
// TODO: Does this really warrant a new synonym? Perhaps "is void" is enough
using empty = void;
// Templates
//
template <template <typename...> class C, typename... Ts>
constexpr auto is(C< Ts...> const& ) -> bool {
return true;
}
#if defined(_MSC_VER)
template <template <typename, typename...> class C, typename T>
constexpr auto is( T const& ) -> bool {
return false;
}
#else
template <template <typename...> class C, typename T>
constexpr auto is( T const& ) -> bool {
return false;
}
#endif
template <template <typename,auto> class C, typename T, auto V>
constexpr auto is( C<T, V> const& ) -> bool {
return true;
}
template <template <typename,auto> class C, typename T>
constexpr auto is( T const& ) -> bool {
return false;
}
// Types
//
template< typename C, typename X >
auto is( X const& ) -> bool {
return false;
}
template< typename C, typename X >
requires std::is_same_v<C, X>
auto is( X const& ) -> bool {
return true;
}
template< typename C, typename X >
requires (std::is_base_of_v<C, X> && !std::is_same_v<C,X>)
auto is( X const& ) -> bool {
return true;
}
template< typename C, typename X >
requires (
( std::is_base_of_v<X, C> ||
( std::is_polymorphic_v<C> && std::is_polymorphic_v<X>)
) && !std::is_same_v<C,X>)
auto is( X const& x ) -> bool {
return Dynamic_cast<C const*>(&x) != nullptr;
}
template< typename C, typename X >
requires (
( std::is_base_of_v<X, C> ||
( std::is_polymorphic_v<C> && std::is_polymorphic_v<X>)
) && !std::is_same_v<C,X>)
auto is( X const* x ) -> bool {
return Dynamic_cast<C const*>(x) != nullptr;
}
template< typename C, typename X >
requires (requires (X x) { *x; X(); } && std::is_same_v<C, empty>)
auto is( X const& x ) -> bool {
return x == X();
}
// Values
//
inline constexpr auto is( auto const& x, auto const& value ) -> bool
{
// Predicate case
if constexpr (requires{ bool{ value(x) }; }) {
return value(x);
}
else if constexpr (std::is_function_v<decltype(value)> || requires{ &value.operator(); }) {
return false;
}
// Value case
else if constexpr (requires{ bool{x == value}; }) {
return x == value;
}
return false;
}
//-------------------------------------------------------------------------------------------------------------
// Built-in as
//
// For use when returning "no such thing", such as
// when customizing "as" for std::variant
struct nonesuch_ {
auto operator==(auto const&) -> bool { return false; }
};
constexpr static nonesuch_ nonesuch;
// The 'as' cast functions are <To, From> so use that order here
// If it's confusing, we can switch this to <From, To>
template< typename To, typename From >
inline constexpr auto is_narrowing_v =
// [dcl.init.list] 7.1
(std::is_floating_point_v<From> && std::is_integral_v<To>) ||
// [dcl.init.list] 7.2
(std::is_floating_point_v<From> && std::is_floating_point_v<To> && sizeof(From) > sizeof(To)) ||
// [dcl.init.list] 7.3
(std::is_integral_v<From> && std::is_floating_point_v<To>) ||
(std::is_enum_v<From> && std::is_floating_point_v<To>) ||
// [dcl.init.list] 7.4
(std::is_integral_v<From> && std::is_integral_v<To> && sizeof(From) > sizeof(To)) ||
(std::is_enum_v<From> && std::is_integral_v<To> && sizeof(From) > sizeof(To)) ||
// [dcl.init.list] 7.5
(std::is_pointer_v<From> && std::is_same_v<To, bool>);
template <typename... Ts>
inline constexpr auto program_violates_type_safety_guarantee = sizeof...(Ts) < 0;
// For literals we can check for safe 'narrowing' at a compile time (e.g., 1 as size_t)
template< typename C, auto x >
inline constexpr bool is_castable_v =
std::is_integral_v<C> &&
std::is_integral_v<CPP2_TYPEOF(x)> &&
!(static_cast<CPP2_TYPEOF(x)>(static_cast<C>(x)) != x ||
(
(std::is_signed_v<C> != std::is_signed_v<CPP2_TYPEOF(x)>) &&
((static_cast<C>(x) < C{}) != (x < CPP2_TYPEOF(x){}))
)
);
// As
//
template< typename C >
auto as(auto const&) -> auto {
return nonesuch;
}
template< typename C, auto x >
requires (std::is_arithmetic_v<C> && std::is_arithmetic_v<CPP2_TYPEOF(x)>)
inline constexpr auto as() -> auto
{
if constexpr ( is_castable_v<C, x> ) {
return static_cast<C>(x);
} else {
return nonesuch;
}
}
template< typename C >
inline constexpr auto as(auto const& x) -> auto
requires (
std::is_floating_point_v<C> &&
std::is_floating_point_v<CPP2_TYPEOF(x)> &&
sizeof(CPP2_TYPEOF(x)) > sizeof(C)
)
{
return nonesuch;
}
// Signed/unsigned conversions to a not-smaller type are handled as a precondition,
// and trying to cast from a value that is in the half of the value space that isn't
// representable in the target type C is flagged as a Type safety contract violation
template< typename C >
inline constexpr auto as(auto const& x CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> auto
requires (
std::is_integral_v<C> &&
std::is_integral_v<CPP2_TYPEOF(x)> &&
std::is_signed_v<CPP2_TYPEOF(x)> != std::is_signed_v<C> &&
sizeof(CPP2_TYPEOF(x)) <= sizeof(C)
)
{
const C c = static_cast<C>(x);
Type.expects( // precondition check: must be round-trippable => not lossy
static_cast<CPP2_TYPEOF(x)>(c) == x && (c < C{}) == (x < CPP2_TYPEOF(x){}),
"dynamic lossy narrowing conversion attempt detected" CPP2_SOURCE_LOCATION_ARG
);
return c;
}
template< typename C, typename X >
requires std::is_same_v<C, X>
auto as( X const& x ) -> decltype(auto) {
return x;
}
template< typename C, typename X >
auto as( X const& x ) -> auto
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