https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89741
Bug ID: 89741 Summary: [Regression] static_assert fires when template not instantiated Product: gcc Version: 9.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: tadeus.prastowo at unitn dot it Target Milestone: --- Consider the following MWE: -- 8< ------------------------ template<typename T1, typename T2> struct Y { static constexpr bool value = false; }; template<> struct Y<void, void> { static constexpr bool value = true; }; template<int x> struct X { static_assert(Y<void, decltype(x)>::value, "1"); }; int main() { } -- 8< ------------------------ Compiling it with GCC 8.3, GCC 7.4, GCC 6.3, GCC 5.5, GCC 4.9.4, Clang 6.0, and Clang 7.0 gives no error (see https://www.godbolt.org/z/t8Dkw7). Compiling it with GCC 9.0 (trunk) gives an error.