https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100667
Viktor Ostashevskyi <ostash at ostash dot kiev.ua> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |ostash at ostash dot kiev.ua --- Comment #1 from Viktor Ostashevskyi <ostash at ostash dot kiev.ua> --- Hello, I have another example, but probably related: #include <tuple> #include <string> class Foo{}; std::tuple<std::string, Foo> bar() { return { {}, Foo{}}; } Fails starting from GCC 11.1 in C++11/14/17/20 modes with the following error: <source>: In function 'std::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, Foo> bar()': <source>:8:23: error: conversion from '<brace-enclosed initializer list>' to 'std::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, Foo>' is ambiguous 8 | return { {}, Foo{}}; | ^ In file included from <source>:1: /opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/tuple:1144:9: note: candidate: 'std::tuple<_T1, _T2>::tuple(std::allocator_arg_t, const _Alloc&) [with _Alloc = Foo; typename std::enable_if<std::_TupleConstraints<std::is_object<_Alloc>::value, _T1, _T2>::__is_implicitly_default_constructible(), bool>::type <anonymous> = true; _T1 = std::__cxx11::basic_string<char>; _T2 = Foo]' 1144 | tuple(allocator_arg_t __tag, const _Alloc& __a) | ^~~~~ /opt/compiler-explorer/gcc-11.1.0/include/c++/11.1.0/tuple:1052:9: note: candidate: 'constexpr std::tuple<_T1, _T2>::tuple(const _T1&, const _T2&) [with bool _Dummy = true; typename std::enable_if<std::_TupleConstraints<_Dummy, _T1, _T2>::__is_implicitly_constructible<const _T1&, const _T2&>(), bool>::type <anonymous> = true; _T1 = std::__cxx11::basic_string<char>; _T2 = Foo]' 1052 | tuple(const _T1& __a1, const _T2& __a2) |