Implement views::transform

tests/std/include/range_algorithm_support.hpp

@@ -415,7 +415,7 @@ namespace test {
             STATIC_ASSERT(always_false<Category>);
         }
 
-        friend void iter_swap(iterator const&, iterator const&) {
+        friend void iter_swap(iterator const&, iterator const&) requires std::is_same_v<Category, output> {
             STATIC_ASSERT(always_false<Category>);
         }
 
@@ -441,8 +441,9 @@ namespace test {
             return std::move(*i.ptr_);
         }
 
-        constexpr friend void iter_swap(iterator const& x, iterator const& y) requires at_least<input> {
-            ranges::iter_swap(x.ptr_, y.ptr_);
+        constexpr friend void iter_swap(iterator const& x, iterator const& y)
+            noexcept(std::is_nothrow_swappable_v<Element>) requires at_least<input> && std::swappable<Element> {
+            ranges::swap(*x.ptr_, *y.ptr_);
         }
 
         // forward iterator operations:
@@ -492,9 +493,14 @@ namespace test {
         [[nodiscard]] constexpr boolish operator>=(iterator const& that) const noexcept requires at_least<random> {
             return !(*this < that);
         }
+        [[nodiscard]] constexpr auto operator<=>(iterator const& that) const noexcept requires at_least<random> {
+            return ptr_ <=> that.ptr_;
+        }
+
         [[nodiscard]] constexpr ReferenceType operator[](ptrdiff_t const n) const& noexcept requires at_least<random> {
             return ReferenceType{ptr_[n]};
         }
+
         constexpr iterator& operator+=(ptrdiff_t const n) & noexcept requires at_least<random> {
             ptr_ += n;
             return *this;
@@ -503,13 +509,15 @@ namespace test {
             ptr_ -= n;
             return *this;
         }
+
         [[nodiscard]] constexpr iterator operator+(ptrdiff_t const n) const noexcept requires at_least<random> {
             return iterator{ptr_ + n};
         }
         [[nodiscard]] friend constexpr iterator operator+(ptrdiff_t const n, iterator const& i) noexcept
             requires at_least<random> {
             return i + n;
         }
+
         [[nodiscard]] constexpr iterator operator-(ptrdiff_t const n) const noexcept requires at_least<random> {
             return iterator{ptr_ - n};
         }

tests/std/test.lst

@@ -327,6 +327,8 @@ tests\P0896R4_views_filter_death
 tests\P0896R4_views_reverse
 tests\P0896R4_views_single
 tests\P0896R4_views_take
+tests\P0896R4_views_transform
+tests\P0896R4_views_transform_death
 tests\P0898R3_concepts
 tests\P0898R3_identity
 tests\P0912R5_coroutine

tests/std/tests/P0896R4_ranges_range_machinery/test.cpp

@@ -95,6 +95,7 @@ STATIC_ASSERT(test_cpo(ranges::views::filter));
 STATIC_ASSERT(test_cpo(ranges::views::reverse));
 STATIC_ASSERT(test_cpo(ranges::views::single));
 STATIC_ASSERT(test_cpo(ranges::views::take));
+STATIC_ASSERT(test_cpo(ranges::views::transform));
 
 void test_cpo_ambiguity() {
     using namespace std::ranges;

tests/std/tests/P0896R4_views_transform/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\strict_concepts_matrix.lst