1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
|
// RUN: %clang_cc1 -std=c++2a -verify %s
// ... return type shall be cv bool ...
namespace not_bool {
struct X {} x;
struct Y {} y;
double operator==(X, Y); // expected-note 4{{here}}
bool a = x == y; // ok
bool b = y == x; // expected-error {{return type 'double' of selected 'operator==' function for rewritten '==' comparison is not 'bool'}}
bool c = x != y; // expected-error {{return type 'double' of selected 'operator==' function for rewritten '!=' comparison is not 'bool'}}
bool d = y != x; // expected-error {{return type 'double' of selected 'operator==' function for rewritten '!=' comparison is not 'bool'}}
// cv-qualifiers are OK
const bool operator==(Y, X);
bool e = y != x; // ok
// We don't prefer a function with bool return type over one witn non-bool return type.
bool f = x != y; // expected-error {{return type 'double' of selected 'operator==' function for rewritten '!=' comparison is not 'bool'}}
// As an extension, we permit integral and unscoped enumeration types too.
// These are used by popular C++ libraries such as ICU.
struct Z {} z;
int operator==(X, Z); // expected-note {{here}}
bool g = z == x; // expected-warning {{ISO C++20 requires return type of selected 'operator==' function for rewritten '==' comparison to be 'bool', not 'int'}}
enum E {};
E operator==(Y, Z); // expected-note {{here}}
bool h = z == y; // expected-warning {{ISO C++20 requires return type of selected 'operator==' function for rewritten '==' comparison to be 'bool', not 'not_bool::E'}}
}
struct X { bool equal; };
struct Y {};
constexpr bool operator==(X x, Y) { return x.equal; }
static_assert(X{true} == Y{});
static_assert(X{false} == Y{}); // expected-error {{failed}}
// x == y -> y == x
static_assert(Y{} == X{true});
static_assert(Y{} == X{false}); // expected-error {{failed}}
// x != y -> !(x == y)
static_assert(X{true} != Y{}); // expected-error {{failed}}
static_assert(X{false} != Y{});
// x != y -> !(y == x)
static_assert(Y{} != X{true}); // expected-error {{failed}}
static_assert(Y{} != X{false});
|
