[libcxx-commits] [libcxx] [libcxx] adds ranges::fold_left_with_iter and ranges::fold_left (PR #75259)

[via libcxx-commits]

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@@ -0,0 +1,171 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// Checks that `std::ranges::fold_left`'s return type is correct.
+
+#include <algorithm>
+#include <concepts>
+#include <functional>
+#include <ranges>
+
+#include "test_iterators.h"
+#include "test_range.h"
+
+template <class Result, class T>
+concept is_T = std::same_as<Result, T>;
+
+using std::ranges::fold_left;
+[[maybe_unused]] auto f = [](int x, double y) { return x * y; };
+
+struct Int {
+  int value;
+};
+
+struct Long {
+  int value;
+
+  Long plus(Int) const;
+};
+
+namespace sentinel_based_ranges {
+template <class T>
+using cpp17_input_range = test_range<cpp17_input_iterator, T>;
+
+static_assert(requires(cpp17_input_range<int> r) {
+  { fold_left(r.begin(), r.end(), 0, std::plus()) } -> std::same_as<int>;
+});
+static_assert(requires(cpp17_input_range<int> r) {
+  { fold_left(r, 0, std::plus()) } -> std::same_as<int>;
+});
+static_assert(requires(cpp17_input_range<int> r) {
+  { fold_left(std::move(r), 0, std::plus()) } -> std::same_as<int>;
+});
+
+template <class T>
+using cpp20_input_range = test_range<cpp20_input_iterator, T>;
+
+static_assert(requires(cpp20_input_range<int> r) {
+  { fold_left(r.begin(), r.end(), 0, std::plus()) } -> std::same_as<int>;
+});
+static_assert(requires(cpp20_input_range<int> r) {
+  { fold_left(r, 0, std::plus()) } -> std::same_as<int>;
+});
+static_assert(requires(cpp20_input_range<int> r) {
+  { fold_left(std::move(r), 0, std::plus()) } -> std::same_as<int>;
+});
+
+template <class T>
+using forward_range = test_range<forward_iterator, T>;
+
+static_assert(requires(forward_range<int> r) {
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EricWF wrote:

Maybe some tests with short that ensure it doesn't promote to int if we don't intend it to?

https://github.com/llvm/llvm-project/pull/75259