clang/test/SemaCXX/cxx2b-overloaded-operator.cpp

   1 // RUN: %clang_cc1 -verify -std=c++23 %s
   2
   3 namespace N {
   4
   5 void empty() {
   6   struct S {
   7     int operator[](); // expected-note{{not viable: requires 0 arguments, but 1 was provided}}
   8   };
   9
  10   S{}[];
  11   S{}[1]; // expected-error {{no viable overloaded operator[] for type 'S'}}
  12 }
  13
  14 void default_var() {
  15   struct S {
  16     constexpr int operator[](int i = 42) { return i; } // expected-note {{not viable: allows at most single argument 'i'}}
  17   };
  18   static_assert(S{}[] == 42);
  19   static_assert(S{}[1] == 1);
  20   static_assert(S{}[1, 2] == 1); // expected-error {{no viable overloaded operator[] for type 'S'}}
  21 }
  22
  23 struct Variadic {
  24   constexpr int operator[](auto... i) { return (42 + ... + i); }
  25 };
  26
  27 void variadic() {
  28
  29   static_assert(Variadic{}[] == 42);
  30   static_assert(Variadic{}[1] == 43);
  31   static_assert(Variadic{}[1, 2] == 45);
  32 }
  33
  34 void multiple() {
  35   struct S {
  36     constexpr int operator[]() { return 0; }
  37     constexpr int operator[](int) { return 1; };
  38     constexpr int operator[](int, int) { return 2; };
  39   };
  40   static_assert(S{}[] == 0);
  41   static_assert(S{}[1] == 1);
  42   static_assert(S{}[1, 1] == 2);
  43 }
  44
  45 void ambiguous() {
  46   struct S {
  47     constexpr int operator[]() { return 0; }         // expected-note{{candidate function}}
  48     constexpr int operator[](int = 0) { return 1; }; // expected-note{{candidate function}}
  49   };
  50
  51   static_assert(S{}[] == 0); // expected-error{{call to subscript operator of type 'S' is ambiguous}}
  52 }
  53 } // namespace N
  54
  55 template <typename... T>
  56 struct T1 {
  57   constexpr auto operator[](T... arg) { // expected-note {{candidate function not viable: requires 2 arguments, but 1 was provided}}
  58     return (1 + ... + arg);
  59   }
  60 };
  61
  62 static_assert(T1<>{}[] == 1);
  63 static_assert(T1<int>{}[1] == 2);
  64 static_assert(T1<int, int>{}[1, 1] == 3);
  65 static_assert(T1<int, int>{}[1] == 3); // expected-error {{no viable overloaded operator[] for type 'T1<int, int>'}}
  66
  67 struct T2 {
  68   constexpr auto operator[](auto... arg) {
  69     return (1 + ... + arg);
  70   }
  71 };
  72
  73 static_assert(T2{}[] == 1);
  74 static_assert(T2{}[1] == 2);
  75 static_assert(T2{}[1, 1] == 3);
  76
  77 namespace test_packs {
  78
  79 struct foo_t {
  80 template<typename... Ts>
  81 constexpr int operator[](Ts... idx) {
  82     return (0 + ... + idx);
  83 }
  84 };
  85
  86 template<int... Is>
  87 constexpr int cxx_subscript() {
  88   foo_t foo;
  89   return foo[Is...];
  90 }
  91
  92 template<int... Is>
  93 int cxx_subscript_unexpanded() {
  94   foo_t foo;
  95   return foo[Is]; // expected-error {{expression contains unexpanded parameter pack 'Is'}}
  96 }
  97
  98 template<int... Is>
  99 constexpr int c_array() {
 100   int arr[] = {1, 2, 3};
 101   return arr[Is...]; // expected-error 2{{type 'int[3]' does not provide a subscript operator}}
 102 }
 103
 104 template<int... Is>
 105 int c_array_unexpanded() {
 106   int arr[] = {1, 2, 3};
 107   return arr[Is]; // expected-error {{expression contains unexpanded parameter pack 'Is'}}
 108 }
 109
 110 void test() {
 111   static_assert(cxx_subscript<1, 2, 3>() == 6);
 112   static_assert(c_array<1>() == 2);
 113
 114   c_array<>(); // expected-note {{in instantiation}}
 115   c_array<1>();
 116   c_array<1, 2>(); // expected-note {{in instantiation}}
 117 }
 118
 119 }