clang/test/SemaTemplate/cxx2a-constraint-caching.cpp

   1 // RUN:  %clang_cc1 -std=c++2a -verify %s
   2 // expected-no-diagnostics
   3
   4 template<typename T>
   5 concept C = (f(T()), true);
   6
   7 template<typename T>
   8 constexpr bool foo() { return false; }
   9
  10 template<typename T>
  11   requires (f(T()), true)
  12 constexpr bool foo() requires (f(T()), true) { return true; }
  13
  14 namespace a {
  15   struct A {};
  16   constexpr void f(A a) {}
  17 }
  18
  19 static_assert(C<a::A>);
  20 static_assert(foo<a::A>());
  21
  22 namespace a {
  23   // This makes calls to f ambiguous, but the second check will still succeed
  24   // because the constraint satisfaction results are cached.
  25   constexpr void f(A a, int = 2) {}
  26 }
  27 static_assert(C<a::A>);
  28 static_assert(foo<a::A>());