clang/test/SemaTemplate/cxx1z-decomposition.cpp

   1 // RUN: %clang_cc1 -std=c++1z -verify %s
   2
   3 struct A { int x, y; };
   4 typedef int B[2];
   5 struct C { template<int> int get(); };
   6 struct D { int x, y, z; };
   7 struct E { int *p, n; };
   8
   9 namespace std {
  10   using size_t = decltype(sizeof(0));
  11   template<typename> struct tuple_size;
  12   template<size_t, typename> struct tuple_element { using type = int; };
  13 }
  14
  15 template<> struct std::tuple_size<C> { enum { value = 2 }; };
  16
  17 template<typename T> int decomp(T &t) {
  18   auto &[a, b] = t; // expected-error {{type 'D' decomposes into 3 elements, but only 2 names were provided}}
  19   return a + b; // expected-error {{cannot initialize return object of type 'int' with an rvalue of type 'int *'}}
  20 }
  21
  22 void test() {
  23   A a;
  24   B b;
  25   C c;
  26   D d;
  27   E e;
  28   decomp(a);
  29   decomp(b);
  30   decomp(c);
  31   decomp(d); // expected-note {{in instantiation of}}
  32   decomp(e); // expected-note {{in instantiation of}}
  33 }