https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91742
--- Comment #8 from Diego Franco <di...@franco-technologies.com> --- So to summarize, these are the main reason why I believe this should be addressed: - init brace works for references of any type: std::vector<int> a {}; std::vector<int>& b {a}; assert(&a == &b); // works int c {}; int& d {c}; assert(&c == &d); // works - init brace works for user defined conversion reference when using static cast: class A { operator const std::vector<int>&() const {return a_;} std::vector<int> a_; }; A a {}; const auto& b {static_cast<const std::vector<int>&>(a)}; assert(&a == &b); // works - init brace does not work for user defined conversion reference WITHOUT static cast: A a {}; const auto& b {a}; assert(&a == &b); // does not work I think the above behavior is quite unexpected, and does not follow any logic of other behaviors in the language. I found this unexpected behavior by running unit tests. Also, semantic wise is correct to use user-defined-conversion without static cast (above example).