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// RUN: %clang_cc1 -verify -std=c++2b %s
namespace N {
void empty() {
struct S {
int operator[](); // expected-note{{not viable: requires 0 arguments, but 1 was provided}}
};
S{}[];
S{}[1]; // expected-error {{no viable overloaded operator[] for type 'S'}}
}
void default_var() {
struct S {
constexpr int operator[](int i = 42) { return i; } // expected-note {{not viable: allows at most single argument 'i'}}
};
static_assert(S{}[] == 42);
static_assert(S{}[1] == 1);
static_assert(S{}[1, 2] == 1); // expected-error {{no viable overloaded operator[] for type 'S'}}
}
struct Variadic {
constexpr int operator[](auto... i) { return (42 + ... + i); }
};
void variadic() {
static_assert(Variadic{}[] == 42);
static_assert(Variadic{}[1] == 43);
static_assert(Variadic{}[1, 2] == 45);
}
void multiple() {
struct S {
constexpr int operator[]() { return 0; }
constexpr int operator[](int) { return 1; };
constexpr int operator[](int, int) { return 2; };
};
static_assert(S{}[] == 0);
static_assert(S{}[1] == 1);
static_assert(S{}[1, 1] == 2);
}
void ambiguous() {
struct S {
constexpr int operator[]() { return 0; } // expected-note{{candidate function}}
constexpr int operator[](int = 0) { return 1; }; // expected-note{{candidate function}}
};
static_assert(S{}[] == 0); // expected-error{{call to subscript operator of type 'S' is ambiguous}}
}
} // namespace N
template <typename... T>
struct T1 {
constexpr auto operator[](T... arg) { // expected-note {{candidate function not viable: requires 2 arguments, but 1 was provided}}
return (1 + ... + arg);
}
};
static_assert(T1<>{}[] == 1);
static_assert(T1<int>{}[1] == 2);
static_assert(T1<int, int>{}[1, 1] == 3);
static_assert(T1<int, int>{}[1] == 3); // expected-error {{no viable overloaded operator[] for type 'T1<int, int>'}}
struct T2 {
constexpr auto operator[](auto... arg) {
return (1 + ... + arg);
}
};
static_assert(T2{}[] == 1);
static_assert(T2{}[1] == 2);
static_assert(T2{}[1, 1] == 3);
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