https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109001
Bug ID: 109001 Summary: “no declaration matches” for complicated non-type template parameters Product: gcc Version: 12.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: headch at gmail dot com Target Milestone: --- I’m reasonably certain (but not completely) that this is valid code: #include <algorithm> #include <cstddef> template<size_t x> class C { public: template<size_t y> C<std::max(x, y)> set(); }; template<size_t x> template<size_t y> C<std::max(x, y)> C<x>::set() { return {}; } however, GCC rejects it with “error: no declaration matches ‘C<std::max<long unsigned int>(x, y)> C<x>::set()’” on the out-of-body function definition. This is accepted in GCC 11.3, as well as the latest versions of Clang and MSVC on gcc.godbolt.org. Interestingly, GCC 12 also accepts the code if I change the function definition (just the definition, not the in-body declaration) to use trailing-return-type syntax: #include <algorithm> #include <cstddef> template<size_t x> class C { public: template<size_t y> C<std::max(x, y)> set(); }; template<size_t x> template<size_t y> auto C<x>::set() -> C<std::max(x, y)> { return {}; }