https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121278
Bug ID: 121278
Summary: comparison of iterators does not compile for
containers of std::expected or std::function that
returns an std::expected
Product: gcc
Version: 15.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jacob.statnekov at gmail dot com
Target Milestone: ---
compiler : gcc 15.1.0
OS : linux 5.4.17-2136.343.5.1.el8uekx86_64 x86_64 GNU/Linux
gcc was built with --enable-languages=c,c++ --prefix=XXX --with-gmp=XXX
--with-mpc=XXX --with-mpfr=XXX --disable-mulitlib
build invocation : -g -o output.s -masm=intel -fno-verbose-asm -S
-fdiagnostics-color=always -std=c++23 example.cpp
compilation error :
In file included from <source>:2:
/opt/compiler-explorer/gcc-15.1.0/include/c++/15.1.0/expected: In substitution
of 'template<class _Up> requires !(__is_expected<_Up>) && requires(const _Tp&
__t, const _Up& __u) {{__t == __u} -> decltype(auto) [requires
std::convertible_to<<placeholder>, bool>];} constexpr bool
std::operator==(const expected<int, __cxx11::basic_string<char> >&, const _Up&)
[with _Up = __gnu_cxx::__normal_iterator<std::expected<int,
std::__cxx11::basic_string<char> >*, std::vector<std::expected<int,
std::__cxx11::basic_string<char> > > >]':
/opt/compiler-explorer/gcc-15.1.0/include/c++/15.1.0/expected:1175:12:
required by substitution of 'template<class _Up> requires
!(__is_expected<_Up>) && requires(const _Tp& __t, const _Up& __u) {{__t == __u}
-> decltype(auto) [requires std::convertible_to<<placeholder>, bool>];}
constexpr bool std::operator==(const expected<int, __cxx11::basic_string<char>
>&, const _Up&) [with _Up = __gnu_cxx::__normal_iterator<std::expected<int,
std::__cxx11::basic_string<char> >*, std::vector<std::expected<int,
std::__cxx11::basic_string<char> > > >]'
1175 | { __t == __u } -> convertible_to<bool>;
| ~~~~^~~~~~
<source>:9:29: required from here
9 | bool isEmpty = begin == end;
| ^~~
/opt/compiler-explorer/gcc-15.1.0/include/c++/15.1.0/expected:1178:2:
required by the constraints of 'template<class _Tp, class _Er> template<class
_Up> requires !(__is_expected<_Up>) && requires(const _Tp& __t, const _Up&
__u) {{__t == __u} -> decltype(auto) [requires
std::convertible_to<<placeholder>, bool>];} constexpr bool
std::operator==(const expected<_Tp, _Er>&, const _Up&)'
/opt/compiler-explorer/gcc-15.1.0/include/c++/15.1.0/expected:1174:7: in
requirements with 'const _Tp& __t', 'const _Up& __u' [with _Tp = int; _Up =
__gnu_cxx::__normal_iterator<std::expected<int,
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >
>*, std::vector<std::expected<int, std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > >,
std::allocator<std::expected<int, std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > > > > >]
/opt/compiler-explorer/gcc-15.1.0/include/c++/15.1.0/expected:1174:14: error:
satisfaction of atomic constraint 'requires(const _Tp& __t, const _Up& __u)
{{__t == __u} -> decltype(auto) [requires std::convertible_to<<placeholder>,
bool>];} [with _Tp = _Tp; _Up = _Up]' depends on itself
1174 | && requires (const _Tp& __t, const _Up& __u) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1175 | { __t == __u } -> convertible_to<bool>;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1176 | }
| ~
Compiler returned: 1
offending code:
#include <vector>
#include <expected>
#include <string>
int main()
{
std::vector<std::expected<int, std::string>> v;
decltype(v)::iterator begin(v.begin()), end(v.end());
bool isEmpty = begin == end; // error here
}
Note :
This constraint error appears for container iterators and containers of
std::functions that return an std::expected. I've tried most of the stl
containers as well as a few boost containers and the constraint error is the
same. Here is a side-by-side comparison of the above code with gcc 14.3 and gcc
15.1 https://godbolt.org/z/3boo43K1W
