https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117849
Bug ID: 117849
Summary: constraint variable in requires expression rejected,
but P2280R4 made it valid
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mkretz at gcc dot gnu.org
Target Milestone: ---
Testcase (https://godbolt.org/z/Mfd85Wcn9):
-------------------
#include <ranges>
#include <array>
#include <vector>
template<typename T>
concept StaticSizedRange = std::ranges::sized_range<T> && requires (T&& t) {
typename std::integral_constant<std::size_t, std::ranges::size(t)>;
};
static_assert(StaticSizedRange<std::array<int, 5>>);
static_assert(StaticSizedRange<std::array<int, 5>&>);
static_assert(StaticSizedRange<const std::array<int, 5>&>);
static_assert(!StaticSizedRange<std::vector<int>>);
-------------------
<source>:7:70: error: template argument 2 is invalid
7 | typename std::integral_constant<std::size_t, std::ranges::size(t)>;
| ^
However, testing 'std::ranges::size(t) >= 0' is valid for the array assertions.
P2280R4 / [expr.const]/10 (https://eel.is/c++draft/expr.const#10) say that this
should work.
