https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118296
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Attachment #60043|0 |1 is obsolete| | Attachment #60044|0 |1 is obsolete| | --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Created attachment 60046 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60046&action=edit Reduced all the way clang errors out: <source>:7:24: error: no viable overloaded operator[] for type 'Array' 7 | int json = Array{}[ { Key{} }, 1]; | ~~~~~~~^ ~~~~~~~~~~~~ <source>:2:19: note: candidate template ignored: substitution failure: deduced incomplete pack <(no value), int> for template parameter 'Js:auto' 2 | constexpr int operator[](auto... Js) const | ^ ~~ And replacing operator[] with a function f, GCC errors out with a similar error message.