[libc++][NFC] Add additional tests for begin/end of std::ranges::take_view

[hawkinsw]

Add additional tests for begin/end of std::ranges::take_view.

In partial fulfillment of #72406.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Will Hawkins (hawkinsw)

Changes

Add a check to make sure that an instance of a take_view::_iterator<false> is returned when the base type is not a simple view nor a sized view.

In partial fulfillment of #72406.

---

Full diff: https://github.com/llvm/llvm-project/pull/79085.diff

2 Files Affected:

• (modified) libcxx/test/std/ranges/range.adaptors/range.take/end.pass.cpp (+21)
• (modified) libcxx/test/std/ranges/range.adaptors/range.take/types.h (+33)

diff --git a/libcxx/test/std/ranges/range.adaptors/range.take/end.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.take/end.pass.cpp
index 6cab05daa9e059a..a54b81c83e6aadb 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.take/end.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.take/end.pass.cpp
@@ -69,6 +69,27 @@ constexpr bool test() {
     assert(tv.end() == std::ranges::next(tv.begin(), 8));
   }
 
+  // Check that (non-)simple, non-sized views have different types for their end() member function.
+  {
+    // These assertions must be true in order to trigger the different paths through the end member function
+    // that will return values with different types:
+    static_assert(!simple_view<NonSimpleViewNonSized>);
+    static_assert(!std::ranges::sized_range<NonSimpleViewNonSized>);
+    static_assert(simple_view<SimpleViewNonSized>);
+    static_assert(std::ranges::range<const SimpleViewNonSized>);
+    static_assert(!std::ranges::sized_range<const SimpleViewNonSized>);
+
+    std::ranges::take_view<NonSimpleViewNonSized> tvns(NonSimpleViewNonSized{buffer, buffer + 8}, 0);
+    std::ranges::take_view<SimpleViewNonSized> tvs(SimpleViewNonSized{buffer, buffer + 8}, 0);
+
+    // __iterator<false> has base with type std::ranges::sentinel_t<NonSimpleViewNonSized>; adding a const qualifier
+    // would change the equality.
+    static_assert(!std::is_same_v<decltype(tvns.end().base()), std::ranges::sentinel_t<const NonSimpleViewNonSized>>);
+    // __iterator<true> has base with type std::ranges::sentinel_t<const NonSimpleViewNonSized>; adding a const qualifier
+    // would not change the equality.
+    static_assert(std::is_same_v<decltype(tvs.end().base()), std::ranges::sentinel_t<const SimpleViewNonSized>>);
+  }
+
   return true;
 }
 
diff --git a/libcxx/test/std/ranges/range.adaptors/range.take/types.h b/libcxx/test/std/ranges/range.adaptors/range.take/types.h
index db80e68bb21afef..083e02ac7cac7ca 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.take/types.h
+++ b/libcxx/test/std/ranges/range.adaptors/range.take/types.h
@@ -65,4 +65,37 @@ struct View : std::ranges::view_base {
   int* end_;
 };
 
+template <bool Simple>
+struct InputView : std::ranges::view_base {
+  constexpr explicit InputView(int* b, int* e) : begin_(b), end_(e) {}
+
+  constexpr common_input_iterator<int*> begin() const { return common_input_iterator<int*>(begin_); }
+  constexpr common_input_iterator<int*> end() const { return common_input_iterator<int*>(end_); }
+
+  constexpr common_input_iterator<const int*> begin()
+    requires(!Simple)
+  {
+    return common_input_iterator<const int*>(begin_);
+  }
+  constexpr common_input_iterator<const int*> end()
+    requires(!Simple)
+  {
+    return common_input_iterator<const int*>(end_);
+  }
+
+private:
+  int* begin_;
+  int* end_;
+};
+
+using NonSimpleViewNonSized = InputView<false>;
+static_assert(std::ranges::view<NonSimpleViewNonSized>);
+static_assert(!simple_view<NonSimpleViewNonSized>);
+static_assert(!std::ranges::sized_range<NonSimpleViewNonSized>);
+
+using SimpleViewNonSized = InputView<true>;
+static_assert(!std::ranges::sized_range<SimpleViewNonSized>);
+static_assert(std::ranges::view<SimpleViewNonSized>);
+static_assert(simple_view<SimpleViewNonSized>);
+
 #endif // TEST_STD_RANGES_RANGE_ADAPTORS_RANGE_TAKE_TYPES_H

[hawkinsw]

Just let me know if there is anything I can add/change to make this more useful!

[hawkinsw]

Just let me know if there is anything I can add/change to make this more useful!

Let me know if there is anything else that I can do to clean this up!

[var-const]

Thanks for the extra tests! Looks great, just some minor comments.

[hawkinsw]

Sorry, @var-const , for the additional review request. As I mentioned in DM, I am just nervous and don't want to screw anything up.

[var-const]

FWIW, I'd use a shorter name (which IMO is fine since it's only used within a single file). It's a super minor comment that's not worth another around of review, so no action necessary. :)