clang/test/Parser/cxx2b-auto-x.cpp

   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 }