Calling views::indices(n) should be expression equivalent to
views::iota(decltype(n)(0), n), which means it should have the same
constraints as views::iota and be SFINAE-friendly.
libstdc++-v3/ChangeLog:
* include/std/ranges (indices::operator()): Constrain using
__can_iota_view concept.
* testsuite/std/ranges/indices/1.cc: Check SFINAE-friendliness
required by expression equivalence. Replace unused <vector>
header with <stddef.h> needed for size_t.
---
This is a tiny tweak for the new views::indices that was added recently.
Tested powerpc64le-linux. Pushed to trunk.
libstdc++-v3/include/std/ranges | 1 +
libstdc++-v3/testsuite/std/ranges/indices/1.cc | 16 +++++++++++++++-
2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 25d2e28e72ff..158692d92a70 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -791,6 +791,7 @@ namespace views
struct _Indices
{
template<ranges::__detail::__is_integer_like _Tp>
+ requires __detail::__can_iota_view<_Tp>
[[nodiscard]] constexpr auto
operator() (_Tp __e) const noexcept
{ return iota(_Tp{}, __e); }
diff --git a/libstdc++-v3/testsuite/std/ranges/indices/1.cc
b/libstdc++-v3/testsuite/std/ranges/indices/1.cc
index 805b29e358f7..038b38f0ce0d 100644
--- a/libstdc++-v3/testsuite/std/ranges/indices/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/indices/1.cc
@@ -4,7 +4,7 @@
#include <ranges>
#include <type_traits>
-#include <vector>
+#include <stddef.h>
template <typename T>
constexpr bool test(T n) {
@@ -29,3 +29,17 @@ int main() {
VERIFY(test<size_t>(44));
static_assert(test<size_t>(44));
}
+
+template<typename T>
+constexpr size_t test_wider(T n)
+{
+ // If indices(n) works, try again with ranges::distance(indices(n)),
+ // which will be a wider type, until we get to an unsupported type.
+ // This verifies that indices(n) is SFINAE-friendly, because otherwise we
+ // would get a hard error outside the immediate context checked by requires.
+ if constexpr (requires { std::views::indices(n); })
+ return test_wider(std::ranges::distance(std::views::indices(n)));
+ return sizeof(T);
+}
+
+static_assert(test_wider(0) > sizeof(long long));
--
2.51.0
