clang/test/SemaCXX/invalid-requirement-requires-expr.cpp

   1 // RUN: %clang -fsyntax-only -std=c++2a -Xclang -verify -ftemplate-depth=5 -ftemplate-backtrace-limit=4 %s
   2
   3 // RequiresExpr contains invalid requirement. (Eg. Highly recurisive template).
   4 template<int x>
   5 struct A { static constexpr bool far(); };
   6 class B {
   7     bool data_member;
   8     friend struct A<1>;
   9 };
  10
  11 template<>
  12 constexpr bool A<0>::far() { return true; }
  13
  14 template<int x>
  15 constexpr bool A<x>::far() {
  16     return requires(B b) {
  17       b.data_member;
  18       requires A<x-1>::far(); // #Invalid
  19       // expected-error@#Invalid {{recursive template instantiation exceeded maximum depth}}
  20       // expected-note@#Invalid {{in instantiation}}
  21       // expected-note@#Invalid 2 {{while}}
  22       // expected-note@#Invalid {{contexts in backtrace}}
  23       // expected-note@#Invalid {{increase recursive template instantiation depth}}
  24     };
  25 }
  26 static_assert(A<1>::far());
  27 static_assert(!A<6>::far()); // expected-note {{in instantiation of member function}}