clang/test/SemaTemplate/subst-into-subst.cpp

   1 // RUN: %clang_cc1 -std=c++2a -verify %s
   2
   3 // When forming and checking satisfaction of atomic constraints, we will
   4 // substitute still-dependent template arguments into an expression, and later
   5 // substitute into the result. This creates some unique situations; check that
   6 // they work.
   7
   8 namespace SubstIntoResolvedTypeTemplateArg {
   9   template<int, class> struct X {};
  10
  11   template<class T> concept A = true;
  12   template<class T> concept B = sizeof(T) != 0;
  13   template<class T> concept C = B<X<1, T>>;
  14
  15   int f(A auto); // expected-note {{candidate}}
  16   int f(C auto); // expected-note {{candidate}}
  17   int k1 = f(0); // expected-error {{ambiguous}}
  18
  19   template<class T> concept D = A<T> && B<X<1, T>>;
  20   int f(D auto);
  21   int k2 = f(0); // ok
  22
  23   // The atomic constraint formed from B<X<(int)'\1', T>> is identical to the
  24   // one formed from C, even though the template arguments are written as
  25   // different expressions; the "equivalent" rules are used rather than the
  26   // "identical" rules when matching template arguments in concept-ids.
  27   template<class T> concept E = A<T> && B<X<(int)'\1', T>>;
  28   int g(C auto);
  29   int g(E auto); // expected-note {{candidate}}
  30   int k3 = g(0);
  31
  32   int g(D auto); // expected-note {{candidate}}
  33   int k4 = g(0); // expected-error {{ambiguous}}
  34 }