https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100979
Bug ID: 100979 Summary: Nested CTAD fails when the outer object is direct initialized and the inner object is list initialized Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: brycelelbach at gmail dot com Target Milestone: --- template <typename T> struct X { X(T t) {} }; int main() { auto t00 = X(1); auto t01 = X{1}; X t02{1}; X t03(1); auto t04 = X(X{1}); auto t05 = X{X{1}}; auto t06 = X(X(1)); auto t07 = X{X(1)}; X t08(X{1}); // GCC 11.x and up rejects this; MSVC and Clang accept it. X t09{X{1}}; X t10(X(1)); X t11{X(1)}; } https://godbolt.org/z/Pbx6cjE7q