llvm-project

1
// RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx23 -std=c++23 -Wpre-c++23-compat %s
2
// RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx20 -std=c++20 %s
3

4
void looks_like_decltype_auto() {
5
  decltype(auto(42)) b = 42; // cxx20-error {{'auto' not allowed here}} \
6
                                cxx23-warning {{'auto' as a functional-style cast is incompatible with C++ standards before C++23}}
7
  decltype(long *) a = 42;   // expected-error {{expected '(' for function-style cast or type construction}} \
8
                                expected-error {{expected expression}}
9
  decltype(auto *) a = 42;   // expected-error {{expected '(' for function-style cast or type construction}} \
10
                                expected-error {{expected expression}}
11
  decltype(auto()) c = 42;   // cxx23-error {{initializer for functional-style cast to 'auto' is empty}} \
12
                                cxx20-error {{'auto' not allowed here}}
13
}
14

15
struct looks_like_declaration {
16
  int n;
17
} a;
18

19
using T = looks_like_declaration *;
20
void f() { T(&a)->n = 1; }
21
void g() { auto(&a)->n = 0; } // cxx23-warning {{before C++23}} \
22
                              // cxx20-error {{declaration of variable 'a' with deduced type 'auto (&)' requires an initializer}} \
23
                              // cxx20-error {{expected ';' at end of declaration}}
24
void h() { auto{&a}->n = 0; } // cxx23-warning {{before C++23}} \
25
                              // cxx20-error {{expected unqualified-id}} \
26
                              // cxx20-error {{expected expression}}
27

28
void e(auto (*p)(int y) -> decltype(y)) {}
29

30
struct M;
31
struct S{
32
    S operator()();
33
    S* operator->();
34
    int N;
35
    int M;
36
} s; // expected-note {{here}}
37

38
void test() {
39
    auto(s)()->N; // cxx23-warning {{expression result unused}} \
40
                  // cxx23-warning {{before C++23}} \
41
                  // cxx20-error {{unknown type name 'N'}}
42
    auto(s)()->M; // expected-error {{redefinition of 's' as different kind of symbol}}
43
}
44

45
void test_paren() {
46
    int a = (auto(0)); // cxx23-warning {{before C++23}} \
47
                       // cxx20-error {{expected expression}} \
48
                       // cxx20-error {{expected ')'}} \
49
                       // cxx20-note  {{to match this '('}}
50
    int b = (auto{0}); // cxx23-warning {{before C++23}} \
51
                       // cxx20-error {{expected expression}} \
52
                       // cxx20-error {{expected ')'}} \
53
                       // cxx20-note  {{to match this '('}}
54
}
55