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
looks_like_decltype_auto()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 *;
f()20 void f() { T(&a)->n = 1; }
g()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}}
h()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
test()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
test_paren()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