[libc++][functional] Test bind_front<NTTP>

Author: JMazurkiewicz

libcxx/test/libcxx/utilities/function.objects/func.bind.partial/bind_front.nttp.nodiscard.verify.cpp

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++26
+
+// <functional>
+
+// Test the libc++ extension that std::bind_front<NTTP> is marked as [[nodiscard]].
+
+#include <functional>
+
+void test() {
+  std::bind_front<test>(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+}

libcxx/test/std/utilities/function.objects/func.bind.partial/bind_front.nttp.pass.cpp

@@ -0,0 +1,355 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++26
+
+// <functional>
+
+// template<auto f, class... Args>
+//   constexpr unspecified bind_front(Args&&...);
+
+#include <functional>
+
+#include <cassert>
+#include <concepts>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "types.h"
+
+constexpr void test_basic_bindings() {
+  { // Bind arguments, call without arguments
+    {
+      auto f = std::bind_front<MakeTuple{}>();
+      assert(f() == std::make_tuple());
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{});
+      assert(f() == std::make_tuple(Elem<1>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{});
+      assert(f() == std::make_tuple(Elem<1>{}, Elem<2>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{}, Elem<3>{});
+      assert(f() == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}));
+    }
+  }
+
+  { // Bind no arguments, call with arguments
+    {
+      auto f = std::bind_front<MakeTuple{}>();
+      assert(f(Elem<1>{}) == std::make_tuple(Elem<1>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>();
+      assert(f(Elem<1>{}, Elem<2>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>();
+      assert(f(Elem<1>{}, Elem<2>{}, Elem<3>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}));
+    }
+  }
+
+  { // Bind arguments, call with arguments
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{});
+      assert(f(Elem<10>{}) == std::make_tuple(Elem<1>{}, Elem<10>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{});
+      assert(f(Elem<10>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<10>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{}, Elem<3>{});
+      assert(f(Elem<10>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}, Elem<10>{}));
+    }
+
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{});
+      assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<1>{}, Elem<10>{}, Elem<11>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{});
+      assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<10>{}, Elem<11>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{}, Elem<3>{});
+      assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}, Elem<10>{}, Elem<11>{}));
+    }
+    {
+      auto f = std::bind_front<MakeTuple{}>(Elem<1>{}, Elem<2>{}, Elem<3>{});
+      assert(f(Elem<10>{}, Elem<11>{}, Elem<12>{}) ==
+             std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}, Elem<10>{}, Elem<11>{}, Elem<12>{}));
+    }
+  }
+
+  { // Basic tests with fundamental types
+    const int n = 2;
+    const int m = 1;
+    int o       = 0;
+
+    auto add       = [](int x, int y) { return x + y; };
+    auto add6      = [](int a, int b, int c, int d, int e, int f) { return a + b + c + d + e + f; };
+    auto increment = [](int& x) { return ++x; };
+
+    auto a = std::bind_front<add>(m, n);
+    assert(a() == 3);
+
+    auto b = std::bind_front<add6>(m, n, m, m, m, m);
+    assert(b() == 7);
+
+    auto c = std::bind_front<add6>(n, m);
+    assert(c(1, 1, 1, 1) == 7);
+
+    auto f = std::bind_front<add>(n);
+    assert(f(3) == 5);
+
+    auto g = std::bind_front<add>(n, 1);
+    assert(g() == 3);
+
+    auto h = std::bind_front<add6>(1, 1, 1);
+    assert(h(2, 2, 2) == 9);
+
+    auto i = std::bind_front<increment>();
+    assert(i(o) == 1);
+    assert(o == 1);
+
+    auto j = std::bind_front<increment>(std::ref(o));
+    assert(j() == 2);
+    assert(o == 2);
+  }
+}
+
+constexpr void test_edge_cases() {
+  { // Make sure we don't treat std::reference_wrapper specially.
+    auto sub = [](std::reference_wrapper<int> a, std::reference_wrapper<int> b) { return a.get() - b.get(); };
+
+    int i  = 1;
+    int j  = 2;
+    auto f = std::bind_front<sub>(std::ref(i));
+    assert(f(std::ref(j)) == -1);
+  }
+
+  { // Make sure we can call a function that's a pointer to a member function.
+    struct MemberFunction {
+      constexpr int mul(int x, int y) { return x * y; }
+    };
+
+    MemberFunction value;
+    auto fn = std::bind_front<&MemberFunction::mul>(value, 2);
+    assert(fn(3) == 6);
+  }
+
+  { // Make sure we can call a function that's a pointer to a member object.
+    struct MemberObject {
+      int obj;
+    };
+
+    MemberObject value{.obj = 3};
+    auto fn1 = std::bind_front<&MemberObject::obj>();
+    assert(fn1(value) == 3);
+    auto fn2 = std::bind_front<&MemberObject::obj>(value);
+    assert(fn2() == 3);
+  }
+}
+
+constexpr void test_passing_arguments() {
+  { // Make sure that we copy the bound arguments into the unspecified-type.
+    int n  = 2;
+    auto f = std::bind_front<[](int x, int y) { return x + y; }>(n, 1);
+    n      = 100;
+    assert(f() == 3);
+  }
+
+  { // Make sure we pass the bound arguments to the function object
+    // with the right value category.
+    {
+      auto was_copied = [](CopyMoveInfo info) { return info.copy_kind == CopyMoveInfo::copy; };
+      CopyMoveInfo info;
+      auto f = std::bind_front<was_copied>(info);
+      assert(f());
+    }
+
+    {
+      auto was_moved = [](CopyMoveInfo info) { return info.copy_kind == CopyMoveInfo::move; };
+      CopyMoveInfo info;
+      auto f = std::bind_front<was_moved>(info);
+      assert(std::move(f)());
+    }
+  }
+}
+
+constexpr void test_perfect_forwarding_call_wrapper() {
+  { // Make sure we call the correctly cv-ref qualified operator()
+    // based on the value category of the bind_front<NTTP> unspecified-type.
+    struct X {
+      constexpr int operator()() & { return 1; }
+      constexpr int operator()() const& { return 2; }
+      constexpr int operator()() && { return 3; }
+      constexpr int operator()() const&& { return 4; }
+    };
+
+    auto f  = std::bind_front<X{}>();
+    using F = decltype(f);
+    assert(static_cast<F&>(f)() == 2);
+    assert(static_cast<const F&>(f)() == 2);
+    assert(static_cast<F&&>(f)() == 2);
+    assert(static_cast<const F&&>(f)() == 2);
+  }
+
+  // Call to `bind_front<NTTP>` unspecified-type's operator() should always result in call to the const& overload of the underlying function object.
+  {
+    { // Make sure unspecified-type is still callable when we delete the & overload.
+      struct X {
+        int operator()() & = delete;
+        int operator()() const&;
+        int operator()() &&;
+        int operator()() const&&;
+      };
+
+      using F = decltype(std::bind_front<X{}>());
+      static_assert(std::invocable<F&>);
+      static_assert(std::invocable<const F&>);
+      static_assert(std::invocable<F>);
+      static_assert(std::invocable<const F>);
+    }
+
+    { // Make sure unspecified-type is not callable when we delete the const& overload.
+      struct X {
+        int operator()() &;
+        int operator()() const& = delete;
+        int operator()() &&;
+        int operator()() const&&;
+      };
+
+      using F = decltype(std::bind_front<X{}>());
+      static_assert(!std::invocable<F&>);
+      static_assert(!std::invocable<const F&>);
+      static_assert(!std::invocable<F>);
+      static_assert(!std::invocable<const F>);
+    }
+
+    { // Make sure unspecified-type is still callable when we delete the && overload.
+      struct X {
+        int operator()() &;
+        int operator()() const&;
+        int operator()() && = delete;
+        int operator()() const&&;
+      };
+
+      using F = decltype(std::bind_front<X{}>());
+      static_assert(std::invocable<F&>);
+      static_assert(std::invocable<const F&>);
+      static_assert(std::invocable<F>);
+      static_assert(std::invocable<const F>);
+    }
+
+    { // Make sure unspecified-type is still callable when we delete the const&& overload.
+      struct X {
+        int operator()() &;
+        int operator()() const&;
+        int operator()() &&;
+        int operator()() const&& = delete;
+      };
+
+      using F = decltype(std::bind_front<X{}>());
+      static_assert(std::invocable<F&>);
+      static_assert(std::invocable<const F&>);
+      static_assert(std::invocable<F>);
+      static_assert(std::invocable<const F>);
+    }
+  }
+
+  { // Test perfect forwarding
+    auto f = [](int& val) {
+      val = 5;
+      return 10;
+    };
+
+    auto bf = std::bind_front<f>();
+    int val = 0;
+    assert(bf(val) == 10);
+    assert(val == 5);
+
+    using BF = decltype(bf);
+    static_assert(std::invocable<BF, int&>);
+    static_assert(!std::invocable<BF, int>);
+  }
+}
+
+constexpr void test_return_type() {
+  { // Test constructors and assignment operators
+    struct LeftShift {
+      constexpr unsigned int operator()(unsigned int x, unsigned int y) const { return x << y; }
+    };
+
+    auto power_of_2 = std::bind_front<LeftShift{}>(1);
+    assert(power_of_2(5) == 32U);
+    assert(power_of_2(4) == 16U);
+
+    auto moved = std::move(power_of_2);
+    assert(moved(6) == 64);
+    assert(moved(7) == 128);
+
+    auto copied = power_of_2;
+    assert(copied(3) == 8);
+    assert(copied(2) == 4);
+
+    moved = std::move(copied);
+    assert(copied(1) == 2);
+    assert(copied(0) == 1);
+
+    copied = moved;
+    assert(copied(8) == 256);
+    assert(copied(9) == 512);
+  }
+
+  { // Make sure `bind_front<NTTP>` unspecified-type's operator() is SFINAE-friendly.
+    using F = decltype(std::bind_front<[](int x, int y) { return x / y; }>(1));
+    static_assert(!std::is_invocable<F>::value);
+    static_assert(std::is_invocable<F, int>::value);
+    static_assert(!std::is_invocable<F, void*>::value);
+    static_assert(!std::is_invocable<F, int, int>::value);
+  }
+
+  { // Test noexceptness
+    auto always_noexcept = std::bind_front<MaybeNoexceptFn<true>{}>();
+    static_assert(noexcept(always_noexcept()));
+
+    auto never_noexcept = std::bind_front<MaybeNoexceptFn<false>{}>();
+    static_assert(!noexcept(never_noexcept()));
+  }
+
+  { // Test calling volatile wrapper
+    using Fn = decltype(std::bind_front<std::integral_constant<int, 0>{}>());
+    static_assert(!std::invocable<volatile Fn&>);
+    static_assert(!std::invocable<const volatile Fn&>);
+    static_assert(!std::invocable<volatile Fn>);
+    static_assert(!std::invocable<const volatile Fn>);
+  }
+}
+
+constexpr bool test() {
+  test_basic_bindings();
+  test_edge_cases();
+  test_passing_arguments();
+  test_perfect_forwarding_call_wrapper();
+  test_return_type();
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert((test(), true));
+
+  return 0;
+}