[libcxx-commits] [PATCH] D111516: [libc++][docs] Mark LWG3274 as complete

[Joe Loser via Phabricator via libcxx-commits]

jloser updated this revision to Diff 378666.
jloser edited the summary of this revision.
jloser added a comment.

Mark `span::empty` as `[[nodiscard]]` and add tests.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111516/new/

https://reviews.llvm.org/D111516

Files:
  libcxx/docs/Status/Cxx20Issues.csv
  libcxx/include/span
  libcxx/test/std/containers/views/span.obs/empty.nodiscard.verify.cpp
  libcxx/test/std/containers/views/span.obs/empty.pass.cpp


Index: libcxx/test/std/containers/views/span.obs/empty.pass.cpp
===================================================================
--- libcxx/test/std/containers/views/span.obs/empty.pass.cpp
+++ libcxx/test/std/containers/views/span.obs/empty.pass.cpp
@@ -13,7 +13,7 @@
 
 // <span>
 
-// constexpr bool empty() const noexcept;
+// [[nodiscard]] constexpr bool empty() const noexcept;
 //
 
 
Index: libcxx/test/std/containers/views/span.obs/empty.nodiscard.verify.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/containers/views/span.obs/empty.nodiscard.verify.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// AppleClang 12.0.0 doesn't fully support ranges/concepts
+// XFAIL: apple-clang-12.0.0
+
+// <span>
+
+// [[nodiscard]] constexpr bool empty() const noexcept;
+//
+
+
+#include <span>
+
+void test() {
+  std::span<int> s1;
+  s1.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  int arr[] = {1, 2, 3};
+  std::span<int, 3> s2{arr};
+  s2.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+}
Index: libcxx/include/span
===================================================================
--- libcxx/include/span
+++ libcxx/include/span
@@ -89,7 +89,7 @@
     // [span.obs], span observers
     constexpr size_type size() const noexcept;
     constexpr size_type size_bytes() const noexcept;
-    constexpr bool empty() const noexcept;
+    [[nodiscard]] constexpr bool empty() const noexcept;
 
     // [span.elem], span element access
     constexpr reference operator[](size_type idx) const;
@@ -332,7 +332,7 @@
 
     _LIBCPP_INLINE_VISIBILITY constexpr size_type size()       const noexcept { return _Extent; }
     _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
-    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()           const noexcept { return _Extent == 0; }
+    [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; }
 
     _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
     {
@@ -503,7 +503,7 @@
 
     _LIBCPP_INLINE_VISIBILITY constexpr size_type size()       const noexcept { return __size; }
     _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); }
-    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()           const noexcept { return __size == 0; }
+    [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; }
 
     _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
     {
Index: libcxx/docs/Status/Cxx20Issues.csv
===================================================================
--- libcxx/docs/Status/Cxx20Issues.csv
+++ libcxx/docs/Status/Cxx20Issues.csv
@@ -183,7 +183,7 @@
 "`3272 <https://wg21.link/LWG3272>`__","``%I%p``\  should parse/format ``duration``\  since midnight","Belfast","",""
 "`3259 <https://wg21.link/LWG3259>`__","The definition of *constexpr iterators* should be adjusted","Belfast","",""
 "`3103 <https://wg21.link/LWG3103>`__","Errors in taking subview of ``span``\  should be ill-formed where possible","Belfast","",""
-"`3274 <https://wg21.link/LWG3274>`__","Missing feature test macro for ``<span>``\ ","Belfast","",""
+"`3274 <https://wg21.link/LWG3274>`__","Missing feature test macro for ``<span>``\ ","Belfast","|Complete|","11.0"
 "`3276 <https://wg21.link/LWG3276>`__","Class ``split_view::outer_iterator::value_type``\  should inherit from ``view_interface``\ ","Belfast","",""
 "`3277 <https://wg21.link/LWG3277>`__","Pre-increment on prvalues is not a requirement of ``weakly_incrementable``\ ","Belfast","",""
 "`3149 <https://wg21.link/LWG3149>`__","``DefaultConstructible``\  should require default initialization","Belfast","|Complete|","13.0"


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