https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99417
Bug ID: 99417 Summary: [C++17] std::variant assignment fails to compile Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: arthur.j.odwyer at gmail dot com Target Milestone: --- // https://godbolt.org/z/b3P6Ta #include <variant> struct Original {}; struct C { C(const Original&); C(C&&) noexcept; C& operator=(const Original&); ~C(); }; void testc(std::variant<C>& vc, const Original& original) { vc = original; } In file included from <source>:1:/include/c++/11.0.1/variant:1445:3: error: call to deleted member function 'operator=' operator=(variant(std::forward<_Tp>(__rhs))); ^~~~~~~~~ <source>:13:8: note: in instantiation of function template specialization 'std::variant<C>::operator=<const Original &>' requested here vc = original; ^ /include/c++/11.0.1/variant:1368:16: note: candidate function has been implicitly deleted variant& operator=(const variant&) = default; ^ /include/c++/11.0.1/variant:1431:2: note: candidate template ignored: requirement '__not_self<std::variant<C> &&>' was not satisfied [with _Tp = std::variant<C>] operator=(_Tp&& __rhs) ^ 1 error generated. Removing the keyword `noexcept` from the move-constructor makes this compile. It compiles fine (with or without `noexcept`) on libc++ and MSVC STL.