https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108047
Sergei Trofimovich <slyfox at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |slyfox at gcc dot gnu.org --- Comment #4 from Sergei Trofimovich <slyfox at gcc dot gnu.org> --- Noticed the same build failure on this week's gcc on apache-arrow-cpp-9.0.0. Extracted small example: namespace std { template <class> class initializer_list; struct Trans_NS___cxx11_basic_string { Trans_NS___cxx11_basic_string(const char *); }; struct vector { vector(initializer_list<Trans_NS___cxx11_basic_string>); }; } // namespace std void key_value_metadata(std::vector, std::vector); template <class> void TestWriteDifferentMetadata() { key_value_metadata({}, {""}); } Not sure if it's valid, but gcc-12 still accepts it. Can re-reduce against clang if needed. $ ./gcc-git/bin/gcc -c bug.cc.cc bug.cc.cc: In function 'void TestWriteDifferentMetadata()': bug.cc.cc:12:21: internal compiler error: unexpected expression '(std::Trans_NS___cxx11_basic_string)""' of kind implicit_conv_expr 12 | key_value_metadata({}, {""}); | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~ 0x219cf54 diagnostic_impl(rich_location*, diagnostic_metadata const*, int, char const*, __va_list_tag (*) [1], diagnostic_t) ???:0 0x219dba6 internal_error(char const*, ...) ???:0 0x9d4fee cxx_eval_constant_expression(constexpr_ctx const*, tree_node*, value_cat, bool*, bool*, tree_node**) ???:0