clang/test/SemaCXX/cxx2a-compat.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -std=c++17 -Wc++20-compat-pedantic -verify %s
   2 // RUN: %clang_cc1 -fsyntax-only -std=c++20 -pedantic -verify %s
   3
   4 struct A { // expected-note 0+{{candidate}}
   5   A() = default; // expected-note 0+{{candidate}}
   6   int x, y;
   7 };
   8 A a1 = {1, 2};
   9 #if __cplusplus <= 201703L
  10   // expected-warning@-2 {{aggregate initialization of type 'A' with user-declared constructors is incompatible with C++20}}
  11 #else
  12   // expected-error@-4 {{no matching constructor}}
  13 #endif
  14 A a2 = {};
  15
  16 struct B : A { A a; };
  17 B b1 = {{}, {}}; // ok
  18 B b2 = {1, 2, 3, 4};
  19 #if __cplusplus <= 201703L
  20   // expected-warning@-2 2{{aggregate initialization of type 'A' with user-declared constructors is incompatible with C++20}}
  21 #else
  22   // expected-error@-4 2{{no viable conversion from 'int' to 'A'}}
  23 #endif
  24
  25 // Essentially any use of a u8 string literal in C++<=17 is broken by C++20.
  26 // Just warn on all such string literals.
  27 struct string { string(const char*); }; // expected-note 0+{{candidate}}
  28 char u8arr[] = u8"hello";
  29 const char *u8ptr = "wo" u8"rld";
  30 string u8str = u8"test" u8"test";
  31 #if __cplusplus <= 201703L
  32 // expected-warning@-4 {{type of UTF-8 string literal will change}} expected-note@-4 {{remove 'u8' prefix}}
  33 // expected-warning@-4 {{type of UTF-8 string literal will change}} expected-note@-4 {{remove 'u8' prefix}}
  34 // expected-warning@-4 {{type of UTF-8 string literal will change}} expected-note@-4 {{remove 'u8' prefix}}
  35 #else
  36 // expected-error@-7 {{cannot initialize a variable of type 'const char *' with an lvalue of type 'const char8_t[6]'}}
  37 // expected-error@-7 {{no viable conversion from 'const char8_t[9]' to 'string'}}
  38 #endif
  39
  40 template<bool b>
  41 struct C {
  42   explicit(C)(int);
  43 };
  44 #if __cplusplus <= 201703L
  45 // expected-warning@-3 {{this expression will be parsed as explicit(bool) in C++20}}
  46 #if defined(__cpp_conditional_explicit)
  47 #error "the feature test macro __cpp_conditional_explicit isn't correct"
  48 #endif
  49 #else
  50 // expected-error@-8 {{does not refer to a value}}
  51 // expected-error@-9 {{expected member name or ';'}}
  52 // expected-error@-10 {{expected ')'}}
  53 // expected-note@-12 {{declared here}}
  54 // expected-note@-12 {{to match this '('}}
  55 #if !defined(__cpp_conditional_explicit) || __cpp_conditional_explicit != 201806L
  56 #error "the feature test macro __cpp_conditional_explicit isn't correct"
  57 #endif
  58 #endif
  59
  60 auto l = []() consteval {};
  61 int consteval();
  62 #if __cplusplus <= 201703L
  63 // expected-warning@-3 {{'consteval' is a keyword in C++20}}
  64 // expected-error@-4 {{expected body of lambda expression}}
  65 #else
  66 // expected-error@-5 {{expected unqualified-id}}
  67 #endif