50 lines · cpp
1// RUN: %clang_cc1 -std=c++2a -verify %s2 3namespace p3 {4 void bar(...);5 template <typename... Args> void foo(Args... args) {6 (void)[... xs = args] {7 bar(xs...);8 };9 }10 11 void use() {12 foo();13 foo(1);14 }15}16 17template<typename ...T> void f(T ...t) {18 (void)[&...x = t] {19 x; // expected-error {{unexpanded parameter pack 'x'}}20 };21 22 // Not OK: can't expand 'x' outside its scope.23 weird((void)[&...x = t] {24 return &x; // expected-error {{unexpanded parameter pack 'x'}}25 }... // expected-error {{does not contain any unexpanded}}26 );27 28 // OK, capture only one 'slice' of 'x'.29 weird((void)[&x = t] {30 return &x;31 }...32 );33 34 // 'x' is not expanded by the outer '...', but 'T' is.35 weird((void)[&... x = t] {36 return T() + &x; // expected-error {{unexpanded parameter pack 'x'}}37 }... // expected-error {{does not contain any unexpanded}}38 );39}40 41template<int ...a> constexpr auto x = [...z = a] (auto F) { return F(z...); };42static_assert(x<1,2,3>([](int a, int b, int c) { return 100 * a + 10 * b + c; }) == 123);43static_assert(x<1,2,3>([](int a, int b, int c) { return 100 * a + 10 * b + c; }) == 124); // expected-error {{failed}} \44 // expected-note {{evaluates to '123 == 124'}}45 46template<int ...a> constexpr auto y = [z = a...] (auto F) { return F(z...); }; // expected-error {{must appear before the name of the capture}}47static_assert(y<1,2,3>([](int a, int b, int c) { return 100 * a + 10 * b + c; }) == 123);48static_assert(y<1,2,3>([](int a, int b, int c) { return 100 * a + 10 * b + c; }) == 124); // expected-error {{failed}} \49 // expected-note {{evaluates to '123 == 124'}}50