[libcxx] adds concept std::derived_from

Implements parts of:
    - P0898R3 Standard Library Concepts
    - P1754 Rename concepts to standard_case for C++20, while we still can

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D74292

diff --git a/libcxx/include/concepts b/libcxx/include/concepts
index b44e8cc..7c42dc8 100644 (file)
--- a/libcxx/include/concepts
+++ b/libcxx/include/concepts
@@ -157,6 +157,12 @@ concept __same_as_impl = _VSTD::_IsSame<_Tp, _Up>::value;
 template<class _Tp, class _Up>
 concept same_as = __same_as_impl<_Tp, _Up> && __same_as_impl<_Up, _Tp>;
 
+// [concept.derived]
+template<class _Dp, class _Bp>
+concept derived_from =
+  is_base_of_v<_Bp, _Dp> &&
+  is_convertible_v<const volatile _Dp*, const volatile _Bp*>;
+
 // [concept.convertible]
 template<class _From, class _To>
 concept convertible_to =

diff --git a/libcxx/test/std/concepts/lang/derived.compile.pass.cpp b/libcxx/test/std/concepts/lang/derived.compile.pass.cpp
new file mode 100644 (file)
index 0000000..1aca4e4
--- /dev/null
+++ b/libcxx/test/std/concepts/lang/derived.compile.pass.cpp
@@ -0,0 +1,498 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class Derived, class Base>
+// concept derived_from;
+
+#include <concepts>
+#include <type_traits>
+
+struct Base1 {};
+struct Derived1 : Base1 {};
+struct Derived2 : Base1 {};
+
+struct DerivedPrivate : private Base1 {};
+struct Derived3 : DerivedPrivate {};
+
+struct DerivedProtected : protected DerivedPrivate {};
+struct Derived4 : DerivedProtected {};
+struct Derived5 : Derived4 {};
+
+template <typename From, typename To>
+constexpr void CheckNotDerivedFromPointer() {
+  { // From as pointer
+    static_assert(!std::derived_from<From*, To>);
+    static_assert(!std::derived_from<From*, const To>);
+    static_assert(!std::derived_from<From*, volatile To>);
+    static_assert(!std::derived_from<From*, const volatile To>);
+
+    if constexpr (!std::same_as<To, void>) {
+      static_assert(!std::derived_from<From*, To&>);
+      static_assert(!std::derived_from<From*, const To&>);
+      static_assert(!std::derived_from<From*, volatile To&>);
+      static_assert(!std::derived_from<From*, const volatile To&>);
+
+      static_assert(!std::derived_from<From*, To&&>);
+      static_assert(!std::derived_from<From*, const To&&>);
+      static_assert(!std::derived_from<From*, volatile To&&>);
+      static_assert(!std::derived_from<From*, const volatile To&&>);
+
+      static_assert(!std::derived_from<const From*, To&>);
+      static_assert(!std::derived_from<const From*, const To&>);
+      static_assert(!std::derived_from<const From*, volatile To&>);
+      static_assert(!std::derived_from<const From*, const volatile To&>);
+
+      static_assert(!std::derived_from<const From*, To&&>);
+      static_assert(!std::derived_from<const From*, const To&&>);
+      static_assert(!std::derived_from<const From*, volatile To&&>);
+      static_assert(!std::derived_from<const From*, const volatile To&&>);
+
+      static_assert(!std::derived_from<volatile From*, To&>);
+      static_assert(!std::derived_from<volatile From*, const To&>);
+      static_assert(!std::derived_from<volatile From*, volatile To&>);
+      static_assert(!std::derived_from<volatile From*, const volatile To&>);
+
+      static_assert(!std::derived_from<volatile From*, To&&>);
+      static_assert(!std::derived_from<volatile From*, const To&&>);
+      static_assert(!std::derived_from<volatile From*, volatile To&&>);
+      static_assert(!std::derived_from<volatile From*, const volatile To&&>);
+
+      static_assert(!std::derived_from<const volatile From*, To&>);
+      static_assert(!std::derived_from<const volatile From*, const To&>);
+      static_assert(!std::derived_from<const volatile From*, volatile To&>);
+      static_assert(
+          !std::derived_from<const volatile From*, const volatile To&>);
+
+      static_assert(!std::derived_from<const volatile From*, To&&>);
+      static_assert(!std::derived_from<const volatile From*, const To&&>);
+      static_assert(!std::derived_from<const volatile From*, volatile To&&>);
+      static_assert(
+          !std::derived_from<const volatile From*, const volatile To&&>);
+    }
+  }
+  { // To as pointer
+    static_assert(!std::derived_from<From, To*>);
+    static_assert(!std::derived_from<From, const To*>);
+    static_assert(!std::derived_from<From, volatile To*>);
+    static_assert(!std::derived_from<From, const volatile To*>);
+
+    if constexpr (!std::same_as<From, void>) {
+      static_assert(!std::derived_from<From&, To*>);
+      static_assert(!std::derived_from<From&, const To*>);
+      static_assert(!std::derived_from<From&, volatile To*>);
+      static_assert(!std::derived_from<From&, const volatile To*>);
+
+      static_assert(!std::derived_from<From&&, To*>);
+      static_assert(!std::derived_from<From&&, const To*>);
+      static_assert(!std::derived_from<From&&, volatile To*>);
+      static_assert(!std::derived_from<From&&, const volatile To*>);
+
+      static_assert(!std::derived_from<const From&, To*>);
+      static_assert(!std::derived_from<const From&, const To*>);
+      static_assert(!std::derived_from<const From&, volatile To*>);
+      static_assert(!std::derived_from<const From&, const volatile To*>);
+
+      static_assert(!std::derived_from<const From&&, To*>);
+      static_assert(!std::derived_from<const From&&, const To*>);
+      static_assert(!std::derived_from<const From&&, volatile To*>);
+      static_assert(!std::derived_from<const From&&, const volatile To*>);
+
+      static_assert(!std::derived_from<volatile From&, To*>);
+      static_assert(!std::derived_from<volatile From&, const To*>);
+      static_assert(!std::derived_from<volatile From&, volatile To*>);
+      static_assert(!std::derived_from<volatile From&, const volatile To*>);
+
+      static_assert(!std::derived_from<volatile From&&, To*>);
+      static_assert(!std::derived_from<volatile From&&, const To*>);
+      static_assert(!std::derived_from<volatile From&&, volatile To*>);
+      static_assert(!std::derived_from<volatile From&&, const volatile To*>);
+
+      static_assert(!std::derived_from<const volatile From&, To*>);
+      static_assert(!std::derived_from<const volatile From&, const To*>);
+      static_assert(!std::derived_from<const volatile From&, volatile To*>);
+      static_assert(
+          !std::derived_from<const volatile From&, const volatile To*>);
+
+      static_assert(!std::derived_from<const volatile From&&, To*>);
+      static_assert(!std::derived_from<const volatile From&&, const To*>);
+      static_assert(!std::derived_from<const volatile From&&, volatile To*>);
+      static_assert(
+          !std::derived_from<const volatile From&&, const volatile To*>);
+    }
+  }
+  { // Both as pointers
+    static_assert(!std::derived_from<From*, To*>);
+    static_assert(!std::derived_from<From*, const To*>);
+    static_assert(!std::derived_from<From*, volatile To*>);
+    static_assert(!std::derived_from<From*, const volatile To*>);
+
+    static_assert(!std::derived_from<const From*, To*>);
+    static_assert(!std::derived_from<const From*, const To*>);
+    static_assert(!std::derived_from<const From*, volatile To*>);
+    static_assert(!std::derived_from<const From*, const volatile To*>);
+
+    static_assert(!std::derived_from<volatile From*, To*>);
+    static_assert(!std::derived_from<volatile From*, const To*>);
+    static_assert(!std::derived_from<volatile From*, volatile To*>);
+    static_assert(!std::derived_from<volatile From*, const volatile To*>);
+
+    static_assert(!std::derived_from<const volatile From*, To*>);
+    static_assert(!std::derived_from<const volatile From*, const To*>);
+    static_assert(!std::derived_from<const volatile From*, volatile To*>);
+    static_assert(!std::derived_from<const volatile From*, const volatile To*>);
+  }
+
+  // From as the return type of a pointer-to-function
+  if constexpr (!std::is_array_v<From>) {
+    static_assert(!std::derived_from<From (*)(), To>);
+    static_assert(!std::derived_from<From (*)(int), To>);
+  }
+
+  // To as the return type of a pointer-to-function
+  if constexpr (!std::is_array_v<To>) {
+    static_assert(!std::derived_from<From, To (*)()>);
+    static_assert(!std::derived_from<From, To (*)(double)>);
+  }
+
+  // Both as the return type of a pointer-to-function
+  if constexpr (!std::is_array_v<From> && !std::is_array_v<To>) {
+    static_assert(!std::derived_from<From (*)(), To (*)()>);
+    static_assert(!std::derived_from<From (*)(int), To (*)(double)>);
+  }
+  { // pointer-to-member
+    if constexpr (std::is_class_v<From> && !std::same_as<To, void>) {
+      static_assert(!std::derived_from<To From::*, To>);
+    }
+
+    if constexpr (std::is_class_v<To> && !std::same_as<From, void>) {
+      static_assert(!std::derived_from<From To::*, From>);
+    }
+  }
+  { // pointer-to-member-functions
+    if constexpr (std::is_class_v<From>) {
+      static_assert(!std::derived_from<From (From::*)(), To>);
+    }
+
+    if constexpr (std::is_class_v<To>) {
+      static_assert(!std::derived_from<To (To::*)(), From>);
+    }
+  }
+}
+
+template <typename From, typename To>
+constexpr void CheckNotDerivedFromReference() {
+  if constexpr (!std::same_as<To, void>) {
+    static_assert(!std::derived_from<From, To&>);
+    static_assert(!std::derived_from<From, const To&>);
+    static_assert(!std::derived_from<From, volatile To&>);
+    static_assert(!std::derived_from<From, const volatile To&>);
+
+    static_assert(!std::derived_from<From, To&&>);
+    static_assert(!std::derived_from<From, const To&&>);
+    static_assert(!std::derived_from<From, volatile To&&>);
+    static_assert(!std::derived_from<From, const volatile To&&>);
+  }
+
+  if constexpr (!std::same_as<From, void>) {
+    static_assert(!std::derived_from<From&, To>);
+    static_assert(!std::derived_from<From&, To>);
+    static_assert(!std::derived_from<From&, To>);
+    static_assert(!std::derived_from<From&, To>);
+
+    static_assert(!std::derived_from<From&&, To>);
+    static_assert(!std::derived_from<From&&, To>);
+    static_assert(!std::derived_from<From&&, To>);
+    static_assert(!std::derived_from<From&&, To>);
+  }
+
+  // From as lvalue references
+  if constexpr (!std::same_as<From, void> && !std::same_as<To, void>) {
+    static_assert(!std::derived_from<From&, To&>);
+    static_assert(!std::derived_from<From&, const To&>);
+    static_assert(!std::derived_from<From&, volatile To&>);
+    static_assert(!std::derived_from<From&, const volatile To&>);
+
+    static_assert(!std::derived_from<From&, To&&>);
+    static_assert(!std::derived_from<From&, const To&&>);
+    static_assert(!std::derived_from<From&, volatile To&&>);
+    static_assert(!std::derived_from<From&, const volatile To&&>);
+
+    static_assert(!std::derived_from<const From&, To&>);
+    static_assert(!std::derived_from<const From&, const To&>);
+    static_assert(!std::derived_from<const From&, volatile To&>);
+    static_assert(!std::derived_from<const From&, const volatile To&>);
+
+    static_assert(!std::derived_from<const From&, To&&>);
+    static_assert(!std::derived_from<const From&, const To&&>);
+    static_assert(!std::derived_from<const From&, volatile To&&>);
+    static_assert(!std::derived_from<const From&, const volatile To&&>);
+
+    static_assert(!std::derived_from<volatile From&, To&>);
+    static_assert(!std::derived_from<volatile From&, const To&>);
+    static_assert(!std::derived_from<volatile From&, volatile To&>);
+    static_assert(!std::derived_from<volatile From&, const volatile To&>);
+
+    static_assert(!std::derived_from<volatile From&, To&&>);
+    static_assert(!std::derived_from<volatile From&, const To&&>);
+    static_assert(!std::derived_from<volatile From&, volatile To&&>);
+    static_assert(!std::derived_from<volatile From&, const volatile To&&>);
+
+    static_assert(!std::derived_from<const volatile From&, To&>);
+    static_assert(!std::derived_from<const volatile From&, const To&>);
+    static_assert(!std::derived_from<const volatile From&, volatile To&>);
+    static_assert(!std::derived_from<const volatile From&, const volatile To&>);
+
+    static_assert(!std::derived_from<const volatile From&, To&&>);
+    static_assert(!std::derived_from<const volatile From&, const To&&>);
+    static_assert(!std::derived_from<const volatile From&, volatile To&&>);
+    static_assert(
+        !std::derived_from<const volatile From&, const volatile To&&>);
+
+    // From as rvalue references
+    static_assert(!std::derived_from<From&&, To&>);
+    static_assert(!std::derived_from<From&&, const To&>);
+    static_assert(!std::derived_from<From&&, volatile To&>);
+    static_assert(!std::derived_from<From&&, const volatile To&>);
+
+    static_assert(!std::derived_from<From&&, To&&>);
+    static_assert(!std::derived_from<From&&, const To&&>);
+    static_assert(!std::derived_from<From&&, volatile To&&>);
+    static_assert(!std::derived_from<From&&, const volatile To&&>);
+
+    static_assert(!std::derived_from<const From&&, To&>);
+    static_assert(!std::derived_from<const From&&, const To&>);
+    static_assert(!std::derived_from<const From&&, volatile To&>);
+    static_assert(!std::derived_from<const From&&, const volatile To&>);
+
+    static_assert(!std::derived_from<const From&&, To&&>);
+    static_assert(!std::derived_from<const From&&, const To&&>);
+    static_assert(!std::derived_from<const From&&, volatile To&&>);
+    static_assert(!std::derived_from<const From&&, const volatile To&&>);
+
+    static_assert(!std::derived_from<volatile From&&, To&>);
+    static_assert(!std::derived_from<volatile From&&, const To&>);
+    static_assert(!std::derived_from<volatile From&&, volatile To&>);
+    static_assert(!std::derived_from<volatile From&&, const volatile To&>);
+
+    static_assert(!std::derived_from<volatile From&&, To&&>);
+    static_assert(!std::derived_from<volatile From&&, const To&&>);
+    static_assert(!std::derived_from<volatile From&&, volatile To&&>);
+    static_assert(!std::derived_from<volatile From&&, const volatile To&&>);
+
+    static_assert(!std::derived_from<const volatile From&&, To&>);
+    static_assert(!std::derived_from<const volatile From&&, const To&>);
+    static_assert(!std::derived_from<const volatile From&&, volatile To&>);
+    static_assert(
+        !std::derived_from<const volatile From&&, const volatile To&>);
+
+    static_assert(!std::derived_from<const volatile From&&, To&&>);
+    static_assert(!std::derived_from<const volatile From&&, const To&&>);
+    static_assert(!std::derived_from<const volatile From&&, volatile To&&>);
+    static_assert(
+        !std::derived_from<const volatile From&&, const volatile To&&>);
+  }
+
+  // From as the return type of a reference-to-function
+  if constexpr (!std::is_array_v<From>) {
+    static_assert(!std::derived_from<From (&)(), To>);
+    static_assert(!std::derived_from<From (&)(int), To>);
+  }
+  // To as the return type of a reference-to-function
+  if constexpr (!std::is_array_v<To>) {
+    static_assert(!std::derived_from<From, To (&)()>);
+    static_assert(!std::derived_from<From, To (&)(double)>);
+  }
+  // Both as the return type of a reference-to-function
+  if constexpr (!std::is_array_v<From> && !std::is_array_v<To>) {
+    static_assert(!std::derived_from<From (&)(), To (&)()>);
+    static_assert(!std::derived_from<From (&)(int), To (&)(double)>);
+  }
+}
+
+template <typename From, typename To>
+constexpr void CheckDerivedFrom() {
+  static_assert(std::derived_from<From, To>);
+
+  static_assert(std::derived_from<From, const To>);
+  static_assert(std::derived_from<From, volatile To>);
+  static_assert(std::derived_from<From, const volatile To>);
+
+  static_assert(std::derived_from<const From, const To>);
+  static_assert(std::derived_from<const From, volatile To>);
+  static_assert(std::derived_from<const From, const volatile To>);
+
+  static_assert(std::derived_from<volatile From, const To>);
+  static_assert(std::derived_from<volatile From, volatile To>);
+  static_assert(std::derived_from<volatile From, const volatile To>);
+
+  static_assert(std::derived_from<const volatile From, const To>);
+  static_assert(std::derived_from<const volatile From, volatile To>);
+  static_assert(std::derived_from<const volatile From, const volatile To>);
+
+  CheckNotDerivedFromPointer<From, To>();
+  CheckNotDerivedFromReference<From, To>();
+}
+
+template <typename From, typename To>
+constexpr void CheckNotDerivedFrom() {
+  static_assert(!std::derived_from<From, To>);
+
+  static_assert(!std::derived_from<From, const To>);
+  static_assert(!std::derived_from<From, volatile To>);
+  static_assert(!std::derived_from<From, const volatile To>);
+
+  static_assert(!std::derived_from<const From, const To>);
+  static_assert(!std::derived_from<const From, volatile To>);
+  static_assert(!std::derived_from<const From, const volatile To>);
+
+  static_assert(!std::derived_from<volatile From, const To>);
+  static_assert(!std::derived_from<volatile From, volatile To>);
+  static_assert(!std::derived_from<volatile From, const volatile To>);
+
+  static_assert(!std::derived_from<const volatile From, const To>);
+  static_assert(!std::derived_from<const volatile From, volatile To>);
+  static_assert(!std::derived_from<const volatile From, const volatile To>);
+
+  CheckNotDerivedFromPointer<From, To>();
+  CheckNotDerivedFromReference<From, To>();
+}
+
+enum Enumeration { Yes, No };
+enum class ScopedEnumeration : int { No, Yes };
+
+int main(int, char**) {
+  { // Fundamentals shouldn't be derived from anything
+    CheckNotDerivedFrom<int, long>();
+    CheckNotDerivedFrom<signed char, char>();
+    CheckNotDerivedFrom<double, Base1>();
+
+    CheckNotDerivedFrom<int, Enumeration>();
+    CheckNotDerivedFrom<int, ScopedEnumeration>();
+
+    CheckNotDerivedFrom<void, void>();
+    CheckNotDerivedFrom<int, int>();
+  }
+  { // Nothing should be derived from a fundamental type
+    CheckNotDerivedFrom<Enumeration, int>();
+    CheckNotDerivedFrom<ScopedEnumeration, int>();
+
+    CheckNotDerivedFrom<Base1, int>();
+    CheckNotDerivedFrom<Base1, double>();
+    CheckNotDerivedFrom<Derived1, char>();
+    CheckNotDerivedFrom<DerivedPrivate, long long>();
+  }
+  { // Other built-in things shouldn't have derivations
+    CheckNotDerivedFrom<Enumeration, Enumeration>();
+    CheckNotDerivedFrom<ScopedEnumeration, ScopedEnumeration>();
+
+    CheckNotDerivedFrom<Enumeration, ScopedEnumeration>();
+    CheckNotDerivedFrom<ScopedEnumeration, Enumeration>();
+
+    CheckNotDerivedFrom<Base1[5], Base1>();
+    CheckNotDerivedFrom<Derived1[5], Base1>();
+
+    CheckNotDerivedFrom<Base1, Base1[5]>();
+    CheckNotDerivedFrom<Derived1, Base1[5]>();
+  }
+
+  { // Base1 is the subject.
+    CheckDerivedFrom<Base1, Base1>();
+
+    CheckNotDerivedFrom<Base1, void>();
+    CheckNotDerivedFrom<Base1, DerivedPrivate>();
+    CheckNotDerivedFrom<Base1, DerivedProtected>();
+    CheckNotDerivedFrom<Base1, Derived1>();
+    CheckNotDerivedFrom<Base1, Derived2>();
+    CheckNotDerivedFrom<Base1, Derived3>();
+    CheckNotDerivedFrom<Base1, Derived4>();
+  }
+
+  { // Derived1 is the subject.
+    CheckDerivedFrom<Derived1, Base1>();
+    CheckDerivedFrom<Derived1, Derived1>();
+
+    CheckNotDerivedFromPointer<Derived1, void>();
+    CheckNotDerivedFrom<Derived1, DerivedPrivate>();
+    CheckNotDerivedFrom<Derived1, DerivedProtected>();
+    CheckNotDerivedFrom<Derived1, Derived2>();
+    CheckNotDerivedFrom<Derived1, Derived3>();
+    CheckNotDerivedFrom<Derived1, Derived4>();
+  }
+
+  { // Derived2 is the subject.
+    CheckDerivedFrom<Derived2, Base1>();
+    CheckDerivedFrom<Derived2, Derived2>();
+
+    CheckNotDerivedFrom<Derived2, DerivedPrivate>();
+    CheckNotDerivedFrom<Derived2, DerivedProtected>();
+    CheckNotDerivedFrom<Derived2, Derived1>();
+    CheckNotDerivedFrom<Derived2, Derived3>();
+    CheckNotDerivedFrom<Derived2, Derived4>();
+  }
+
+  { // DerivedPrivate is the subject.
+    CheckDerivedFrom<DerivedPrivate, DerivedPrivate>();
+
+    CheckNotDerivedFrom<DerivedPrivate, Base1>();
+    CheckNotDerivedFrom<DerivedPrivate, DerivedProtected>();
+    CheckNotDerivedFrom<DerivedPrivate, Derived1>();
+    CheckNotDerivedFrom<DerivedPrivate, Derived2>();
+    CheckNotDerivedFrom<DerivedPrivate, Derived3>();
+    CheckNotDerivedFrom<DerivedPrivate, Derived4>();
+  }
+
+  { // Derived3 is the subject.
+    CheckDerivedFrom<Derived3, DerivedPrivate>();
+    CheckDerivedFrom<Derived3, Derived3>();
+
+    CheckNotDerivedFrom<Derived3, Base1>();
+    CheckNotDerivedFrom<Derived3, DerivedProtected>();
+    CheckNotDerivedFrom<Derived3, Derived1>();
+    CheckNotDerivedFrom<Derived3, Derived2>();
+    CheckNotDerivedFrom<Derived3, Derived4>();
+  }
+
+  { // DerivedProtected is the subject.
+    CheckDerivedFrom<DerivedProtected, DerivedProtected>();
+
+    CheckNotDerivedFromPointer<DerivedProtected, Base1>();
+    CheckNotDerivedFromPointer<DerivedProtected, DerivedPrivate>();
+    CheckNotDerivedFromPointer<DerivedProtected, Derived1>();
+    CheckNotDerivedFromPointer<DerivedProtected, Derived2>();
+    CheckNotDerivedFromPointer<DerivedProtected, Derived3>();
+    CheckNotDerivedFromPointer<DerivedProtected, Derived4>();
+  }
+
+  { // Derived4 is the subject.
+    CheckDerivedFrom<Derived4, DerivedProtected>();
+    CheckDerivedFrom<Derived4, Derived4>();
+
+    CheckNotDerivedFrom<Derived4, Base1>();
+    CheckNotDerivedFrom<Derived4, DerivedPrivate>();
+    CheckNotDerivedFrom<Derived4, Derived1>();
+    CheckNotDerivedFrom<Derived4, Derived2>();
+    CheckNotDerivedFrom<Derived4, Derived3>();
+  }
+
+  { // Derived5 is the subject.
+    CheckDerivedFrom<Derived5, DerivedProtected>();
+    CheckDerivedFrom<Derived5, Derived4>();
+    CheckDerivedFrom<Derived5, Derived5>();
+
+    CheckNotDerivedFrom<Derived5, Base1>();
+    CheckNotDerivedFrom<Derived5, DerivedPrivate>();
+    CheckNotDerivedFrom<Derived5, Derived1>();
+    CheckNotDerivedFrom<Derived5, Derived2>();
+    CheckNotDerivedFrom<Derived5, Derived3>();
+  }
+
+  return 0;
+}