gcc/testsuite/g++.dg/concepts/diagnostic9.C

// PR c++/85278
// { dg-do compile { target concepts } }

// { dg-message "candidate: .*const decltype\\(f2::a\\)&&" "" { target *-*-* } .+2 }
template<typename T>
void f2(T a)
  requires requires (const decltype(a) &&x) { -x; }
{ }

int main() {
  f2<void*>(nullptr); // { dg-error "no match" }
}