[libc++][ranges][NFC] Test that range algorithms support iterators requiring `iter_move`.

[huixie90]

libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp

119

binary_func seem to return bool and transform would write these bools to the output. I guess it works for the int overload because bool is convertible to int. But for MoveOnly overload, it probably doesn't work.

[var-const]

Address feedback

[ldionne]

I'm happy with this approach (using a template and if constexpr to opt-out a few checks). However, if we end up having to add a lot more if constexpr, I would strongly consider copy-pasting the function instead to avoid adding too much logic in the tests. For the sake of keeping tests easy to validate.

libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp

 #include <array>
 #include <concepts>
 #include <initializer_list>
 #include <iterator>
 #include <memory>
 #include <random>
 #include <ranges>
 
+#include "MoveOnly.h"
 #include "test_iterators.h"
 
 template <class Func, std::ranges::range Input, class ...Args>
 constexpr void test(Func&& func, Input& in, Args&& ...args) {
   func(in.begin(), in.end(), std::forward<Args>(args)...);
   func(in, std::forward<Args>(args)...);
 }
 
 template <class Func, std::ranges::range Range1, std::ranges::range Range2, class ...Args>
 constexpr void test(Func&& func, Range1& r1, Range2& r2, Args&& ...args) {
   func(r1.begin(), r1.end(), r2.begin(), r2.end(), std::forward<Args>(args)...);
   func(r1, r2, std::forward<Args>(args)...);
 }
 
 template <class Func, std::ranges::range Input, class ...Args>
 constexpr void test_mid(Func&& func, Input& in, std::ranges::iterator_t<Input> mid, Args&& ...args) {
   func(in.begin(), mid, in.end(), std::forward<Args>(args)...);
   func(in, mid, std::forward<Args>(args)...);
 }
 
-constexpr bool test_all() {
-  std::array input = {1, 2, 3};
+template <class T>
+constexpr void run_tests() {
+  std::array input = {T{1}, T{2}, T{3}};
   ProxyRange in{input};
-  std::array input2 = {4, 5, 6};
+  std::array input2 = {T{4}, T{5}, T{6}};
   ProxyRange in2{input2};
 
   auto mid = in.begin() + 1;
 
-  std::array output = {4, 5, 6, 7, 8, 9};
+  std::array output = {T{4}, T{5}, T{6}, T{7}, T{8}, T{9}};
   ProxyIterator out{output.begin()};
   //auto out2 = output.begin() + 1;
 
-  int num = 2;
-  Proxy<int&> x{num};
+  T num{2};
+  Proxy<T&> x{num};
   int count = 1;
 
-  auto unary_pred = [](const Proxy<int>& val) { return val.getData() > 0; };
-  //auto binary_pred = [](const Proxy<int>& lhs, const Proxy<int>& rhs) { return lhs.getData() == rhs.getData(); };
-  auto binary_func = [](const Proxy<int>& lhs, const Proxy<int>&) -> Proxy<int> { return lhs.getData(); };
-  //auto gen = [] { return Proxy<int>(42); };
+  auto unary_pred = [](const Proxy<T&>&) { return true; };
+  //auto binary_pred = [](const Proxy<T>&, const Proxy<T>&) { return return false; };
+  auto binary_func = [](const Proxy<T>&, const Proxy<T>&) -> Proxy<T> { return Proxy<T>(T()); };
+  //auto gen = [] { return Proxy<T>(T{42}); };
   //std::mt19937 rand_gen;
 
   test(std::ranges::any_of, in, unary_pred);
   test(std::ranges::all_of, in, unary_pred);
   test(std::ranges::none_of, in, unary_pred);
   test(std::ranges::find, in, x);
   test(std::ranges::find_if, in, unary_pred);
   test(std::ranges::find_if_not, in, unary_pred);
constexpr void run_tests() {
   test(std::ranges::is_sorted, in);
   test(std::ranges::is_sorted_until, in);
   //test(std::ranges::includes, in, in2);
   //test(std::ranges::is_heap, in);
   //test(std::ranges::is_heap_until, in);
   //test(std::ranges::is_permutation, in, in2);
   test(std::ranges::for_each, in, std::identity{});
   std::ranges::for_each_n(in.begin(), count, std::identity{});
+  if constexpr (std::copyable<T>) {
     test(std::ranges::copy, in, out);
     std::ranges::copy_n(in.begin(), count, out);
     test(std::ranges::copy_if, in, out, unary_pred);
     // TODO: uncomment `copy_backward` once https://reviews.llvm.org/D128864 lands.
     //test(std::ranges::copy_backward, in, out);
+  }
   test(std::ranges::move, in, out);
   // TODO: uncomment `move_backward` once https://reviews.llvm.org/D128864 lands.
   // test(std::ranges::move_backward, in, out);
+  if constexpr (std::copyable<T>) {
     test(std::ranges::fill, in, x);
     std::ranges::fill_n(in.begin(), count, x);
     test(std::ranges::transform, in, out, std::identity{});
     test(std::ranges::transform, in, in2, out, binary_func);
+  }
   //test(std::ranges::generate, in, gen);
   //std::ranges::generate_n(in.begin(), count, gen);
+  if constexpr (std::copyable<T>) {
   //test(std::ranges::remove_copy, in, out, x);
   //test(std::ranges::remove_copy_if, in, out, unary_pred);
     test(std::ranges::replace, in, x, x);
     test(std::ranges::replace_if, in, unary_pred, x);
     //test(std::ranges::replace_copy, in, out, x, x);
     //test(std::ranges::replace_copy_if, in, out, unary_pred, x);
-  //test(std::ranges::swap_ranges, in, in2);
+  }
+  test(std::ranges::swap_ranges, in, in2);
+  if constexpr (std::copyable<T>) {
     test(std::ranges::reverse_copy, in, out);
     test_mid(std::ranges::rotate_copy, in, mid, out);
-  //test(std::ranges::sample, in, out, count, rand_gen);
     //test(std::ranges::unique_copy, in, out);
     //test(std::ranges::partition_copy, in, out, out2, unary_pred);
     //test_mid(std::ranges::partial_sort_copy, in, in2);
     test(std::ranges::merge, in, in2, out);
     test(std::ranges::set_difference, in, in2, out);
     test(std::ranges::set_intersection, in, in2, out);
     test(std::ranges::set_symmetric_difference, in, in2, out);
     test(std::ranges::set_union, in, in2, out);
+  }
   test(std::ranges::remove, in, x);
   test(std::ranges::remove_if, in, unary_pred);
   test(std::ranges::reverse, in);
   //test_mid(std::ranges::rotate, in, mid);
   //test(std::ranges::shuffle, in, rand_gen);
+  //test(std::ranges::sample, in, out, count, rand_gen);
   //test(std::ranges::unique, in);
   //test(std::ranges::partition, in, binary_pred);
   //if (!std::is_constant_evaluated())
   //  test(std::ranges::stable_partition, in, binary_pred);
   test(std::ranges::sort, in);
   // TODO: `stable_sort` requires `ranges::rotate` to be implemented.
   //if (!std::is_constant_evaluated())
   //  test(std::ranges::stable_sort, in);
   //test_mid(std::ranges::partial_sort, in, mid);
   test_mid(std::ranges::nth_element, in, mid);
   //if (!std::is_constant_evaluated())
   //  test_mid(std::ranges::inplace_merge, in, mid);
   test(std::ranges::make_heap, in);
   test(std::ranges::push_heap, in);
   test(std::ranges::pop_heap, in);
   test(std::ranges::sort_heap, in);
   //test(std::ranges::prev_permutation, in);
   //test(std::ranges::next_permutation, in);
 
   // The algorithms that work on uninitialized memory have constraints that prevent proxy iterators from being used with
   // them.
+}
+
+constexpr bool test_all() {
+  run_tests<int>();
+  run_tests<MoveOnly>();
 
   return true;
 }
 
 int main(int, char**) {
   test_all();
   static_assert(test_all());
 
   return 0;
 }

libcxx/test/support/MoveOnly.h

friend TEST_CONSTEXPR bool operator< (const MoveOnly& x, const MoveOnly& y)
         { return x.data_ <  y.data_; }
     friend TEST_CONSTEXPR bool operator<=(const MoveOnly& x, const MoveOnly& y)
         { return x.data_ <= y.data_; }
     friend TEST_CONSTEXPR bool operator> (const MoveOnly& x, const MoveOnly& y)
         { return x.data_ >  y.data_; }
     friend TEST_CONSTEXPR bool operator>=(const MoveOnly& x, const MoveOnly& y)
         { return x.data_ >= y.data_; }
 
+#if TEST_STD_VER > 17
+    friend constexpr auto operator<=>(const MoveOnly&, const MoveOnly&) = default;
+#endif // TEST_STD_VER > 17
+
     TEST_CONSTEXPR_CXX14 MoveOnly operator+(const MoveOnly& x) const
         { return MoveOnly(data_ + x.data_); }
     TEST_CONSTEXPR_CXX14 MoveOnly operator*(const MoveOnly& x) const
         { return MoveOnly(data_ * x.data_); }
 
     template<class T, class U>
     friend void operator,(T t, U u) = delete;
 };