https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97600
--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
I think all views whose begin()/end() has a placeholder return type and
performs direct initialization of a _Iterator/_Sentinel from *this are affected
by some variant of this issue.
A library-side workaround would be to templatize view_interface::operator
bool() like so:
diff --git a/libstdc++-v3/include/bits/ranges_util.h
b/libstdc++-v3/include/bits/ranges_util.h
index cc50e2ad4e4..8563a5dfcb0 100644
--- a/libstdc++-v3/include/bits/ranges_util.h
+++ b/libstdc++-v3/include/bits/ranges_util.h
@@ -86,13 +86,15 @@ namespace ranges
empty() const requires forward_range<const _Derived>
{ return ranges::begin(_M_derived()) == ranges::end(_M_derived()); }
- constexpr explicit
- operator bool() requires requires { ranges::empty(_M_derived()); }
- { return !ranges::empty(_M_derived()); }
-
- constexpr explicit
- operator bool() const requires requires { ranges::empty(_M_derived()); }
- { return !ranges::empty(_M_derived()); }
+ template<same_as<bool> _Tp>
+ constexpr explicit
+ operator _Tp() requires requires { ranges::empty(_M_derived()); }
+ { return !ranges::empty(_M_derived()); }
+
+ template<same_as<bool> _Tp>
+ constexpr explicit
+ operator _Tp() const requires requires { ranges::empty(_M_derived()); }
+ { return !ranges::empty(_M_derived()); }
constexpr auto
data() requires contiguous_iterator<iterator_t<_Derived>>
So that when we considering this conversion function in step 5, we deduce
_Tp=_Iterator and short circuit satisfaction of the conversion function's
associated constraints in step 6.
