https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107168
Bug ID: 107168 Summary: Wrong errors for concepts with default lambda not-type argument Product: gcc Version: 12.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: fchelnokov at gmail dot com Target Milestone: --- The following code in accepted in Clang and MSVC, but GCC emits seemingly wrong errors: template <typename, auto = []{}> concept x = true; struct S { // GCC error: template argument 2 is invalid operator x auto() { return 42; } // GCC error: wrong number of template arguments (0, should be at least 1) operator x<> auto() const { return 43; } }; Online demo: https://godbolt.org/z/a3494qrG3