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      1 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify -fcxx-exceptions %s
      2 
      3 // An explicitly-defaulted function may be declared constexpr only if it would
      4 // have been implicitly declared as constexpr.
      5 struct S1 {
      6   constexpr S1() = default; // expected-error {{defaulted definition of default constructor is not constexpr}}
      7   constexpr S1(const S1&) = default;
      8   constexpr S1(S1&&) = default;
      9   constexpr S1 &operator=(const S1&) const = default; // expected-error {{explicitly-defaulted copy assignment operator may not have}}
     10   constexpr S1 &operator=(S1&&) const = default; // expected-error {{explicitly-defaulted move assignment operator may not have}}
     11   constexpr ~S1() = default; // expected-error {{destructor cannot be marked constexpr}}
     12   int n;
     13 };
     14 struct NoCopyMove {
     15   constexpr NoCopyMove() {}
     16   NoCopyMove(const NoCopyMove&);
     17   NoCopyMove(NoCopyMove&&);
     18 };
     19 struct S2 {
     20   constexpr S2() = default;
     21   constexpr S2(const S2&) = default; // expected-error {{defaulted definition of copy constructor is not constexpr}}
     22   constexpr S2(S2&&) = default; // expected-error {{defaulted definition of move constructor is not constexpr}}
     23   NoCopyMove ncm;
     24 };
     25 
     26 // If a function is explicitly defaulted on its first declaration
     27 //   -- it is implicitly considered to be constexpr if the implicit declaration
     28 //      would be
     29 struct S3 {
     30   S3() = default;
     31   S3(const S3&) = default;
     32   S3(S3&&) = default;
     33   constexpr S3(int n) : n(n) {}
     34   int n;
     35 };
     36 constexpr S3 s3a = S3(0);
     37 constexpr S3 s3b = s3a;
     38 constexpr S3 s3c = S3();
     39 constexpr S3 s3d; // expected-error {{default initialization of an object of const type 'const S3' requires a user-provided default constructor}}
     40 
     41 struct S4 {
     42   S4() = default;
     43   S4(const S4&) = default; // expected-note {{here}}
     44   S4(S4&&) = default; // expected-note {{here}}
     45   NoCopyMove ncm;
     46 };
     47 constexpr S4 s4a{}; // ok
     48 constexpr S4 s4b = S4(); // expected-error {{constant expression}} expected-note {{non-constexpr constructor}}
     49 constexpr S4 s4c = s4a; // expected-error {{constant expression}} expected-note {{non-constexpr constructor}}
     50 
     51 struct S5 {
     52   constexpr S5();
     53   int n = 1, m = n + 3;
     54 };
     55 constexpr S5::S5() = default;
     56 static_assert(S5().m == 4, "");
     57 
     58 
     59 // An explicitly-defaulted function may have an exception specification only if
     60 // it is compatible with the exception specification on an implicit declaration.
     61 struct E1 {
     62   E1() noexcept = default;
     63   E1(const E1&) noexcept = default;
     64   E1(E1&&) noexcept = default;
     65   E1 &operator=(const E1&) noexcept = default;
     66   E1 &operator=(E1&&) noexcept = default;
     67   ~E1() noexcept = default;
     68 };
     69 struct E2 {
     70   E2() noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted default constructor does not match the calculated one}}
     71   E2(const E2&) noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted copy constructor does not match the calculated one}}
     72   E2(E2&&) noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted move constructor does not match the calculated one}}
     73   E2 &operator=(const E2&) noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted copy assignment operator does not match the calculated one}}
     74   E2 &operator=(E2&&) noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted move assignment operator does not match the calculated one}}
     75   ~E2() noexcept(false) = default; // expected-error {{exception specification of explicitly defaulted destructor does not match the calculated one}}
     76 };
     77 
     78 // If a function is explicitly defaulted on its first declaration
     79 //   -- it is implicitly considered to have the same exception-specification as
     80 //      if it had been implicitly declared
     81 struct E3 {
     82   E3() = default;
     83   E3(const E3&) = default;
     84   E3(E3&&) = default;
     85   E3 &operator=(const E3&) = default;
     86   E3 &operator=(E3&&) = default;
     87   ~E3() = default;
     88 };
     89 E3 e3;
     90 static_assert(noexcept(E3(), E3(E3()), E3(e3), e3 = E3(), e3 = e3), "");
     91 struct E4 {
     92   E4() noexcept(false);
     93   E4(const E4&) noexcept(false);
     94   E4(E4&&) noexcept(false);
     95   E4 &operator=(const E4&) noexcept(false);
     96   E4 &operator=(E4&&) noexcept(false);
     97   ~E4() noexcept(false);
     98 };
     99 struct E5 {
    100   E5() = default;
    101   E5(const E5&) = default;
    102   E5(E5&&) = default;
    103   E5 &operator=(const E5&) = default;
    104   E5 &operator=(E5&&) = default;
    105   ~E5() = default;
    106 
    107   E4 e4;
    108 };
    109 E5 e5;
    110 static_assert(!noexcept(E5()), "");
    111 static_assert(!noexcept(E5(static_cast<E5&&>(e5))), "");
    112 static_assert(!noexcept(E5(e5)), "");
    113 static_assert(!noexcept(e5 = E5()), "");
    114 static_assert(!noexcept(e5 = e5), "");
    115 
    116 namespace PR13492 {
    117   struct B {
    118     B() = default;
    119   };
    120 
    121   void f() {
    122     const B b; // expected-error {{default initialization of an object of const type 'const PR13492::B' requires a user-provided default constructor}}
    123   }
    124 }
    125