clang/test/SemaCXX/bool-increment-SFINAE.cpp

   1 // RUN: %clang_cc1 %std_cxx98-14 -fsyntax-only -verify=precxx17 %s
   2 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify=expected %s
   3 // RUN: %clang_cc1 -std=c++17 -DFAILED_CXX17 -fsyntax-only -verify=failcxx17 %s
   4 // RUN: %clang_cc1 %std_cxx20- -fsyntax-only -verify=cxx20 %s
   5 // expected-no-diagnostics
   6
   7 template<class T> auto f(T t) -> decltype(++t); // precxx17-warning {{incrementing expression of type bool is deprecated}}
   8
   9 auto f(...) -> void;
  10 void g() { f(true); }
  11
  12 #ifdef FAILED_CXX17
  13
  14 template<class T> auto f1(T t) -> decltype(++t); // failcxx17-note {{candidate template ignored: substitution failure [with T = bool]: ISO C++17 does not allow incrementing expression of type bool}}
  15 auto f1(void) -> void; // failcxx17-note {{candidate function not viable: requires 0 arguments, but 1 was provided}}
  16 void g1() { f1(true); } // failcxx17-error {{no matching function for call to 'f1'}}
  17
  18 #endif
  19
  20 #if __cplusplus >= 202002L
  21 template <class T>
  22 concept can_increment = requires(T t) {
  23   ++t;
  24 };
  25
  26 template <class T>
  27 void f() {
  28   static_assert(requires(T t) { ++t; }); // cxx20-error {{static assertion failed due to requirement 'requires (bool t) { <<error-expression>>; }'}}
  29 }
  30
  31 int main() {
  32   f<bool>(); // cxx20-note {{in instantiation of function template specialization 'f<bool>' requested here}}
  33   static_assert(!can_increment<bool>);
  34
  35   return 0;
  36 }
  37 #endif