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libstdc++: Remove constraints from std::optional monadic ops [PR102863]

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The constraints on transform and and_then can cause errors when checking
satisfaction. The constraints that were present in R6 of the paper were
moved for he final F8 revision, and so should have been included in the
implementation.

libstdc++-v3/ChangeLog:

	PR libstdc++/102863
	* include/std/optional (optional::and_then, optional::transform):
	Remove requires-clause.
	* testsuite/20_util/optional/monadic/and_then.cc: Check
	overload resolution doesn't cause errors.
	* testsuite/20_util/optional/monadic/transform.cc: Likewise.
This commit is contained in:
Jonathan Wakely 2021-10-21 01:19:45 +01:00
parent 674dda6be0
commit 0fac85a24f
3 changed files with 32 additions and 8 deletions
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16
libstdc++-v3/include/std/optional
View File

@ -1048,7 +1048,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// [optional.monadic]
template<typename _Fn> requires invocable<_Fn, _Tp&>
template<typename _Fn>
constexpr auto
and_then(_Fn&& __f) &
{
@ -1060,7 +1060,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return _Up();
}
template<typename _Fn> requires invocable<_Fn, const _Tp&>
template<typename _Fn>
constexpr auto
and_then(_Fn&& __f) const &
{
@ -1072,7 +1072,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return _Up();
}
template<typename _Fn> requires invocable<_Fn, _Tp>
template<typename _Fn>
constexpr auto
and_then(_Fn&& __f) &&
{
@ -1084,7 +1084,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return _Up();
}
template<typename _Fn> requires invocable<_Fn, const _Tp>
template<typename _Fn>
constexpr auto
and_then(_Fn&& __f) const &&
{
@ -1096,7 +1096,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return _Up();
}
template<typename _Fn> requires invocable<_Fn, _Tp&>
template<typename _Fn>
constexpr auto
transform(_Fn&& __f) &
{
@ -1107,7 +1107,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return optional<_Up>();
}
template<typename _Fn> requires invocable<_Fn, const _Tp&>
template<typename _Fn>
constexpr auto
transform(_Fn&& __f) const &
{
@ -1118,7 +1118,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return optional<_Up>();
}
template<typename _Fn> requires invocable<_Fn, _Tp>
template<typename _Fn>
constexpr auto
transform(_Fn&& __f) &&
{
@ -1129,7 +1129,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return optional<_Up>();
}
template<typename _Fn> requires invocable<_Fn, const _Tp>
template<typename _Fn>
constexpr auto
transform(_Fn&& __f) const &&
{

12
libstdc++-v3/testsuite/20_util/optional/monadic/and_then.cc
View File

@ -113,8 +113,20 @@ test_forwarding()
static_assert( test_forwarding() );
void f(int&) { }
void
test_unconstrained()
{
// PR libstc++/102863 - Optional monadic ops should not be constrained
std::optional<int> x;
auto answer = x.and_then([](auto& y) { f(y); return std::optional<int>{42}; });
VERIFY( !answer );
}
int main()
{
test_and_then();
test_forwarding();
test_unconstrained();
}

12
libstdc++-v3/testsuite/20_util/optional/monadic/transform.cc
View File

@ -132,9 +132,21 @@ test_copy_elision()
static_assert( test_copy_elision() );
void f(int&) { }
void
test_unconstrained()
{
// PR libstc++/102863 - Optional monadic ops should not be constrained
std::optional<int> x;
auto answer = x.transform([](auto& y) { f(y); return 42; });
VERIFY( !answer );
}
int main()
{
test_transform();
test_forwarding();
test_copy_elision();
test_unconstrained();
}