clang/test/SemaTemplate/lambda-capture-pack.cpp

   1 // RUN: %clang_cc1 -std=c++2a -verify %s
   2
   3 template<typename ...T, typename ...Lambda> void check_sizes(Lambda ...L) {
   4   static_assert(((sizeof(T) == sizeof(Lambda)) && ...));
   5 }
   6
   7 template<typename ...T> void f(T ...v) {
   8   // Pack expansion of lambdas: each lambda captures only one pack element.
   9   check_sizes<T...>([=] { (void)&v; } ...);
  10
  11   // Pack expansion inside lambda: captures all pack elements.
  12   auto l = [=] { ((void)&v, ...); };
  13   static_assert(sizeof(l) >= (sizeof(T) + ...));
  14 }
  15
  16 template void f(int, char, double);
  17
  18 namespace PR41576 {
  19   template <class... Xs> constexpr int f(Xs ...xs) {
  20     return [&](auto ...ys) { // expected-note {{instantiation}}
  21       return ((xs + ys), ...); // expected-warning {{left operand of comma operator has no effect}}
  22     }(1, 2);
  23   }
  24   static_assert(f(3, 4) == 6); // expected-note {{instantiation}}
  25 }