[libcxx-commits] [libcxx] 4dd901f - [libc++] Fix the noexceptness of __decay_copy.

[Arthur O'Dwyer via libcxx-commits]

Author: Arthur O'Dwyer
Date: 2021-12-13T17:55:38-05:00
New Revision: 4dd901f4d3aa072309eb23fbd8497f7916f7d77c

URL: https://github.com/llvm/llvm-project/commit/4dd901f4d3aa072309eb23fbd8497f7916f7d77c
DIFF: https://github.com/llvm/llvm-project/commit/4dd901f4d3aa072309eb23fbd8497f7916f7d77c.diff

LOG: [libc++] Fix the noexceptness of __decay_copy.

When `a` was an array type, `__decay_copy(a)` was incorrectly marking itself
noexcept(false), because it is false that `int[10]` is nothrow convertible to `int[10]`
(in fact it is not convertible at all).

We have no tests explicitly for `__decay_copy`, but the new ranges::begin
and ranges::end tests fail before this patch.

Differential Revision: https://reviews.llvm.org/D115658

Added: 
    

Modified: 
    libcxx/include/__utility/decay_copy.h
    libcxx/test/std/ranges/range.access/range.access.begin/begin.pass.cpp
    libcxx/test/std/ranges/range.access/range.access.end/end.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__utility/decay_copy.h b/libcxx/include/__utility/decay_copy.h
index 5c9716a892798..32238e117f561 100644
--- a/libcxx/include/__utility/decay_copy.h
+++ b/libcxx/include/__utility/decay_copy.h
@@ -24,7 +24,7 @@ template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
 typename decay<_Tp>::type __decay_copy(_Tp&& __t)
 #if _LIBCPP_STD_VER > 17
-    noexcept(is_nothrow_convertible_v<_Tp, remove_reference_t<_Tp>>)
+    noexcept(is_nothrow_convertible_v<_Tp, decay_t<_Tp>>)
 #endif
 {
   return _VSTD::forward<_Tp>(__t);

diff  --git a/libcxx/test/std/ranges/range.access/range.access.begin/begin.pass.cpp b/libcxx/test/std/ranges/range.access/range.access.begin/begin.pass.cpp
index 04f30c8143596..3b712a1cc1377 100644
--- a/libcxx/test/std/ranges/range.access/range.access.begin/begin.pass.cpp
+++ b/libcxx/test/std/ranges/range.access/range.access.begin/begin.pass.cpp
@@ -264,6 +264,13 @@ ASSERT_NOEXCEPT(std::ranges::cbegin(std::declval<NoThrowADLBegin<int*>&>()));
 ASSERT_NOT_NOEXCEPT(std::ranges::begin(std::declval<NoThrowADLBegin<ThrowingIterator<int>>&>()));
 ASSERT_NOT_NOEXCEPT(std::ranges::cbegin(std::declval<NoThrowADLBegin<ThrowingIterator<int>>&>()));
 
+struct BeginReturnsArrayRef {
+    auto begin() const noexcept -> int(&)[10];
+    auto end() const noexcept -> int(&)[10];
+} brar;
+static_assert(noexcept(std::ranges::begin(brar)));
+static_assert(noexcept(std::ranges::cbegin(brar)));
+
 
 int main(int, char**) {
   testArray();

diff  --git a/libcxx/test/std/ranges/range.access/range.access.end/end.pass.cpp b/libcxx/test/std/ranges/range.access/range.access.end/end.pass.cpp
index f860442af4fbe..dd5da2ebf5944 100644
--- a/libcxx/test/std/ranges/range.access/range.access.end/end.pass.cpp
+++ b/libcxx/test/std/ranges/range.access/range.access.end/end.pass.cpp
@@ -298,6 +298,13 @@ ASSERT_NOEXCEPT(std::ranges::cend(std::declval<NoThrowADLEnd<int*>&>()));
 ASSERT_NOT_NOEXCEPT(std::ranges::end(std::declval<NoThrowADLEnd<ThrowingIterator<int>>&>()));
 ASSERT_NOT_NOEXCEPT(std::ranges::cend(std::declval<NoThrowADLEnd<ThrowingIterator<int>>&>()));
 
+struct BeginReturnsArrayRef {
+    auto begin() const noexcept -> int(&)[10];
+    auto end() const noexcept -> int(&)[10];
+} brar;
+static_assert(noexcept(std::ranges::end(brar)));
+static_assert(noexcept(std::ranges::cend(brar)));
+
 
 int main(int, char**) {
   testArray();