text: // RUN: %clang_cc1 -std=c++1z -verify %s
  
  void use_from_own_init() {
    auto [a] = a; // expected-error {{binding 'a' cannot appear in the initializer of its own decomposition declaration}}
  }
  
  // As a Clang extension, _Complex can be decomposed.
  float decompose_complex(_Complex float cf) {
    static _Complex float scf;
    auto &[sre, sim] = scf;
    // ok, this is references initialized by constant expressions all the way down
    static_assert(&sre == &__real scf);
    static_assert(&sim == &__imag scf);
  
    auto [re, im] = cf;
    return re*re + im*im;
  }
  
  // As a Clang extension, vector types can be decomposed.
  typedef float vf3 __attribute__((ext_vector_type(3)));
  float decompose_vector(vf3 v) {
    auto [x, y, z] = v;
    auto *p = &x; // expected-error {{address of vector element requested}}
    return x + y + z;
  }
  
  struct S { int a, b; };
  constexpr int f(S s) {
    auto &[a, b] = s;
    return a * 10 + b;
  }
  static_assert(f({1, 2}) == 12);
  
  constexpr bool g(S &&s) { 
    auto &[a, b] = s;
    return &a == &s.a && &b == &s.b && &a != &b;
  }
  static_assert(g({1, 2}));
  
  void enclosing() {
    struct S { int a; };
    auto [n] = S(); // expected-note 2{{'n' declared here}}
  
    struct Q { int f() { return n; } }; // expected-error {{reference to local binding 'n' declared in enclosing function}}
    // FIXME: This is probably supposed to be valid, but we do not have clear rules on how it's supposed to work.
    (void) [&] { return n; }; // expected-error {{reference to local binding 'n' declared in enclosing function}}
    (void) [n] {}; // expected-error {{'n' in capture list does not name a variable}}
  }
  
  void bitfield() {
    struct { int a : 3, : 4, b : 5; } a;
    auto &[x, y] = a;
    auto &[p, q, r] = a; // expected-error {{decomposes into 2 elements, but 3 names were provided}}
  }
  
  void for_range() {
    int x = 1;
    for (auto[a, b] : x) { // expected-error {{invalid range expression of type 'int'; no viable 'begin' function available}}
      a++;
    }
  
    int y[5];
    for (auto[c] : y) { // expected-error {{cannot decompose non-class, non-array type 'int'}}
      c++;
    }
  }
  
  int error_recovery() {
    auto [foobar]; // expected-error {{requires an initializer}}
    return foobar_; // expected-error {{undeclared identifier 'foobar_'}}
  }
  
  // FIXME: by-value array copies
  