https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108047
--- Comment #6 from Sergei Trofimovich <slyfox at gcc dot gnu.org> --- Encountered very similar ICE, this time on toml library on this week's gcc-13 master. Reduced it down to the following: // $ cat bug.cc #include <string> #include <vector> void format_underline(std::vector<std::string>); template <typename> void parse_key_value_pair(void) { format_underline({""}); } $ g++ -c bug.cc ... bug.cc: In function 'void parse_key_value_pair()': bug.cc:7:51: internal compiler error: unexpected expression '(std::__cxx11::basic_string<char>)""' of kind implicit_conv_expr 7 | void parse_key_value_pair(void) { format_underline({""}); } | ~~~~~~~~~~~~~~~~^~~~~~ 0x1cbb294 diagnostic_impl(rich_location*, diagnostic_metadata const*, int, char const*, __va_list_tag (*) [1], diagnostic_t) ???:0 0x1cbbee6 internal_error(char const*, ...) ???:0 0x79c770 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*, value_cat, bool*, bool*, tree_node**) ???:0 0x7a1572 cxx_eval_outermost_constant_expr(tree_node*, bool, bool, bool, bool, tree_node*) ???:0 0x7a52e6 maybe_constant_init_1(tree_node*, tree_node*, bool, bool) ???:0 0x77a767 build_user_type_conversion_1(tree_node*, tree_node*, int, int) ???:0