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libstdc++: Implement LWG 3404 for C++20 subrange [PR 100044]

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These deduction guides became useless with LWG 3282 (implemented in
commit r10-6741) and so were removed by LWG 3404.

libstdc++-v3/ChangeLog:

	PR libstdc++/100044
	* include/bits/ranges_util.h (__detail::__iterator_sentinel_pair):
	Remove helper concept.
	(subrange(_Pr), subrange(Pr, __make_unsigned_like<...>)): Remove
	deduction guides, as per LWG 3404.
	* testsuite/std/ranges/subrange/lwg3282_neg.cc: Check that class
	template argument deduction fails.
This commit is contained in:
Jonathan Wakely 2021-04-12 12:49:17 +01:00
parent 1c35444b91
commit 7569ce583f
2 changed files with 13 additions and 15 deletions
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15
libstdc++-v3/include/bits/ranges_util.h
View file

@ -186,11 +186,6 @@ namespace ranges
&& __convertible_to_non_slicing<_Up, tuple_element_t<0, _Tp>>
&& convertible_to<_Vp, tuple_element_t<1, _Tp>>;
template<typename _Tp>
concept __iterator_sentinel_pair
= !range<_Tp> && __pair_like<_Tp>
&& sentinel_for<tuple_element_t<1, _Tp>, tuple_element_t<0, _Tp>>;
} // namespace __detail
enum class subrange_kind : bool { unsized, sized };
@ -352,16 +347,6 @@ namespace ranges
__detail::__make_unsigned_like_t<iter_difference_t<_It>>)
-> subrange<_It, _Sent, subrange_kind::sized>;
template<__detail::__iterator_sentinel_pair _Pr>
subrange(_Pr)
-> subrange<tuple_element_t<0, _Pr>, tuple_element_t<1, _Pr>>;
template<__detail::__iterator_sentinel_pair _Pr>
subrange(_Pr, __detail::__make_unsigned_like_t<iter_difference_t<
tuple_element_t<0, _Pr>>>)
-> subrange<tuple_element_t<0, _Pr>, tuple_element_t<1, _Pr>,
subrange_kind::sized>;
template<borrowed_range _Rng>
subrange(_Rng&&)
-> subrange<iterator_t<_Rng>, sentinel_t<_Rng>,

13
libstdc++-v3/testsuite/std/ranges/subrange/lwg3282_neg.cc
View file

@ -29,3 +29,16 @@ struct Base {};
struct Derived : Base {};
subrange<Derived*> sd;
subrange<Base*> sb = sd; // { dg-error "conversion" }
void
test_lwg3404()
{
// LWG 3404. Finish removing subrange's conversions from pair-like
std::pair<char*, char*> p;
subrange sb1(p); // { dg-error "no matching function" }
// { dg-error "class template argument deduction" "" { target *-*-* } 38 }
subrange sb2(p, p.second - p.first); // { dg-error "no matching function" }
// { dg-error "class template argument deduction" "" { target *-*-* } 40 }
// { dg-prune-output "in requirements with" }
}