libstdc++: Make ranges::size and ranges::empty check for unbounded arrays
Passing IncompleteType(&)[] to ranges::begin produces an error outside the immediate context, which is fine for ranges::begin, but it means that we fail to enforce the SFINAE-able constraints for ranges::size and ranges::size. They should not be callable for any array of unknown bound, whether the type is complete or not. Because we don't enforce that in their constraints, we get a hard error when they try to use ranges::begin. This simply adds explicit checks for arrays of unknown bound to the constraints for ranges::size and ranges::empty. We only need to check it for the __sentinel_size and __eq_iter_empty concepts, because those are the ones that are relevant to arrays, and which try to use ranges::begin. libstdc++-v3/ChangeLog: * include/bits/ranges_base.h (ranges::size, ranges::empty): Add explicit check for unbounded arrays before using ranges::begin. * testsuite/std/ranges/access/empty.cc: Check handling of unbounded arrays. * testsuite/std/ranges/access/size.cc: Likewise.
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@ -383,6 +383,8 @@ namespace ranges
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template<typename _Tp>
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concept __sentinel_size = requires(_Tp& __t)
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{
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requires (!is_unbounded_array_v<remove_reference_t<_Tp>>);
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{ _Begin{}(__t) } -> forward_iterator;
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{ _End{}(__t) } -> sized_sentinel_for<decltype(_Begin{}(__t))>;
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@ -466,6 +468,8 @@ namespace ranges
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template<typename _Tp>
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concept __eq_iter_empty = requires(_Tp& __t)
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{
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requires (!is_unbounded_array_v<remove_reference_t<_Tp>>);
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{ _Begin{}(__t) } -> forward_iterator;
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bool(_Begin{}(__t) == _End{}(__t));
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@ -121,6 +121,16 @@ test04()
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static_assert( ! noexcept(std::ranges::empty(E3{})) );
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}
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template<typename T>
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concept has_empty = requires (T& t) { std::ranges::empty(t); };
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// If T is an array of unknown bound, ranges::empty(E) is ill-formed.
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static_assert( ! has_empty<int[]> );
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static_assert( ! has_empty<int(&)[]> );
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static_assert( ! has_empty<int[][2]> );
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struct Incomplete;
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static_assert( ! has_empty<Incomplete[]> );
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int
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main()
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{
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@ -122,6 +122,16 @@ test06()
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static_assert( std::ranges::size(R{}) == 42 );
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}
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template<typename T>
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concept has_size = requires (T& t) { std::ranges::size(t); };
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// If T is an array of unknown bound, ranges::size(E) is ill-formed.
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static_assert( ! has_size<int[]> );
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static_assert( ! has_size<int(&)[]> );
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static_assert( ! has_size<int[][2]> );
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struct Incomplete;
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static_assert( ! has_size<Incomplete[]> );
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int
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main()
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{
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