// RUN: %clang_cc1 %s -fsyntax-only -std=c++23                                     -verify=expected,new
// RUN: %clang_cc1 %s -fsyntax-only -std=c++23 -fno-relaxed-template-template-args -verify=expected,old

namespace issue1 {
  template<class T, class U = T> class B {};
  template<template<class> class P, class T> void f(P<T>);
  // new-note@-1 {{deduced type 'B<[...], (default) int>' of 1st parameter does not match adjusted type 'B<[...], float>' of argument [with P = B, T = int]}}
  // old-note@-2 2{{template template argument has different template parameters}}

  void g() {
    f(B<int>()); // old-error {{no matching function for call}}
    f(B<int,float>()); // expected-error {{no matching function for call}}
  }
} // namespace issue1

namespace issue2 {
  template<typename> struct match;

  template<template<typename> class t,typename T> struct match<t<T>>;

  template<template<typename,typename> class t,typename T0,typename T1>
  struct match<t<T0,T1>> {};

  template<typename,typename = void> struct other {};
  template struct match<other<void,void>>;
} // namespace issue2

namespace type {
  template<class T1, class T2 = float> struct A;

  template<class T3> struct B;
  template<template<class T4          > class TT1, class T5          > struct B<TT1<T5    >>   ;
  template<template<class T6, class T7> class TT2, class T8, class T9> struct B<TT2<T8, T9>> {};
  template struct B<A<int>>;
} // namespace type

namespace value {
  template<class T1, int V1 = 1> struct A;

  template<class T2> struct B;
  template<template<class T3        > class TT1, class T4        > struct B<TT1<T4    >>   ;
  template<template<class T5, int V2> class TT2, class T6, int V3> struct B<TT2<T6, V3>> {};
  template struct B<A<int>>;
} // namespace value

namespace templ {
  template <class T1> struct A;

  template<class T2, template <class T3> class T4 = A> struct B {};

  template<class T5> struct C;

  template<template<class T6> class TT1, class T7> struct C<TT1<T7>>;

  template<template<class T8, template <class T9> class> class TT2,
    class T10, template <class T11> class TT3>
  struct C<TT2<T10, TT3>> {};

  template struct C<B<int>>;
} // namespace templ

namespace class_template {
  template <class T1, class T2 = float> struct A;

  template <class T3> struct B;

  template <template <class T4> class TT1, class T5> struct B<TT1<T5>>;

  template <class T6, class T7> struct B<A<T6, T7>> {};

  template struct B<A<int>>;
} // namespace class_template

namespace class_template_func {
  template <class T1, class T2 = float> struct A {};

  template <template <class T4> class TT1, class T5> void f(TT1<T5>);
  template <class T6, class T7>                      void f(A<T6, T7>) {};

  void g() {
    f(A<int>());
  }
} // namespace class_template_func

namespace type_pack1 {
  template<class T2> struct A;
  template<template<class ...T3s> class TT1, class T4> struct A<TT1<T4>>   ;
  template<template<class    T5 > class TT2, class T6> struct A<TT2<T6>> {};

  template<class T1> struct B;
  template struct A<B<char>>;
} // namespace type_pack1

namespace type_pack2 {
  template<class T2> struct A;
  template<template<class ...T3s> class TT1, class ...T4> struct A<TT1<T4...>>   ;
  template<template<class    T5 > class TT2, class ...T6> struct A<TT2<T6...>> {};

  template<class T1> struct B;
  template struct A<B<char>>;
} // namespace type_pack2

namespace type_pack3 {
  template<class T1, class T2 = float> struct A;

  template<class T3> struct B;

  template<template<class T4              > class TT1, class T5              > struct B<TT1<T5        >>;

  template<template<class T6, class ...T7s> class TT2, class T8, class ...T9s> struct B<TT2<T8, T9s...>> {};

  template struct B<A<int>>;
} // namespace type_pack3

namespace gcc_issue {
  template<class T1, class T2> struct A;

  template<template<class T1> class TT1, class T2> struct A<TT1<T2>, typename TT1<T2>::type>;
  // new-note@-1 {{partial specialization matches}}

  template<template<class T3, class T4> class TT2, class T5, class T6>
  struct A<TT2<T5, T6>, typename TT2<T5, T5>::type>;
  // new-note@-1 {{partial specialization matches}}
  // old-note@-2 {{template is declared here}}

  template <class T7, class T8 = T7> struct B { using type = int; };

  template struct A<B<int>, int>;
  // new-error@-1 {{ambiguous partial specializations}}
  // old-error@-2 {{explicit instantiation of undefined template}}
} // namespace gcc_issue

namespace ttp_defaults {
  template <template <class T1> class TT1> struct A {};
  // old-note@-1 2{{previous template template parameter}}

  template <template <class T2> class TT2> void f(A<TT2>);
  // new-note@-1 {{explicit instantiation candidate}}
  // old-note@-2 {{invalid explicitly-specified argument for template parameter 'TT2'}}

  // FIXME: The default arguments on the TTP are not available during partial ordering.
  template <template <class T3, class T4 = float> class TT3> void f(A<TT3>) {};
  // new-note@-1 {{explicit instantiation candidate}}
  // old-error@-2 {{template template argument has different template parameters}}
  // old-note@-3 {{too many template parameters}}

  template <class T5, class T6 = int> struct B;
  // old-note@-1 {{too many template parameters}}

  template void f<B>(A<B>);
  // new-error@-1 {{partial ordering for explicit instantiation of 'f' is ambiguous}}
  // old-error@-2 {{template template argument has different template parameters}}
  // old-error@-3 {{explicit instantiation of 'f' does not refer to a function template}}
} // namespace ttp_defaults

namespace ttp_only {
  template <template <class...    > class TT1> struct A      { static constexpr int V = 0; };
  template <template <class       > class TT2> struct A<TT2> { static constexpr int V = 1; };
  template <template <class, class> class TT3> struct A<TT3> { static constexpr int V = 2; };

  template <class ...          > struct B;
  template <class              > struct C;
  template <class, class       > struct D;
  template <class, class, class> struct E;

  static_assert(A<B>::V == 0);
  static_assert(A<C>::V == 1);
  static_assert(A<D>::V == 2);
  static_assert(A<E>::V == 0);
} // namespace ttp_only

namespace consistency {
  template<class T> struct nondeduced { using type = T; };
  template<class T8, class T9 = float> struct B;

  namespace t1 {
    template<class T1, class T2, class T3> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3, class T4>
    struct A<TT1<T1, T2>, TT1<T3, T4>, typename nondeduced<TT1<T1, T2>>::type> {};

    template<template<class> class UU1,
             template<class> class UU2,
             class U1, class U2>
    struct A<UU1<U1>, UU2<U2>, typename nondeduced<UU1<U1>>::type>;

    template struct A<B<int>, B<int>, B<int>>;
  } // namespace t1
  namespace t2 {
    template<class T1, class T2, class T3> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3, class T4>
    struct A<TT1<T1, T2>, TT1<T3, T4>, typename nondeduced<TT1<T1, T4>>::type> {};
    // new-note@-1 {{partial specialization matches}}

    template<template<class> class UU1,
             template<class> class UU2,
             class U1, class U2>
    struct A<UU1<U1>, UU2<U2>, typename nondeduced<UU1<U1>>::type>;
    // new-note@-1 {{partial specialization matches}}

    template struct A<B<int>, B<int>, B<int>>;
    // new-error@-1 {{ambiguous partial specializations}}
  } // namespace t2
  namespace t3 {
    template<class T1, class T2, class T3> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3, class T4>
    struct A<TT1<T1, T2>, TT1<T3, T4>, typename nondeduced<TT1<T1, T2>>::type> {};
    // new-note@-1 {{partial specialization matches}}

    template<template<class> class UU1,
             class U1, class U2>
    struct A<UU1<U1>, UU1<U2>, typename nondeduced<UU1<U1>>::type>;
    // new-note@-1 {{partial specialization matches}}

    template struct A<B<int>, B<int>, B<int>>;
    // new-error@-1 {{ambiguous partial specializations}}
  } // namespace t3
  namespace t4 {
    template<class T1, class T2, class T3> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3, class T4>
    struct A<TT1<T1, T2>, TT1<T3, T4>, typename nondeduced<TT1<T1, T4>>::type> {};
    // new-note@-1 {{partial specialization matches}}

    template<template<class> class UU1,
             class U1, class U2>
    struct A<UU1<U1>, UU1<U2>, typename nondeduced<UU1<U1>>::type>;
    // new-note@-1 {{partial specialization matches}}

    template struct A<B<int>, B<int>, B<int>>;
    // new-error@-1 {{ambiguous partial specializations}}
  } // namespace t4
  namespace t5 {
    template<class T1, class T2> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3, class T4>
    struct A<TT1<T1, T2>, TT1<T3, T4>> {};
    // new-note@-1 {{partial specialization matches}}

    template<template<class> class UU1,
             class U1, class U2>
    struct A<UU1<U1>, UU1<U2>>;
    // new-note@-1 {{partial specialization matches}}

    template struct A<B<int>, B<int>>;
    // new-error@-1 {{ambiguous partial specializations}}
  } // namespace t5
  namespace t6 {
    template<class T1, class T2> struct A;

    template<template<class, class> class TT1,
             class T1, class T2, class T3>
    struct A<TT1<T1, T2>, TT1<T1, T3>> {};
    // new-note@-1 {{partial specialization matches}}

    template<template<class> class UU1,
             class U1, class U2>
    struct A<UU1<U1>, UU1<U2>>;
    // new-note@-1 {{partial specialization matches}}

    template struct A<B<int>, B<int>>;
    // new-error@-1 {{ambiguous partial specializations}}
  } // namespace t6
} // namespace consistency

namespace classes {
  namespace canon {
    template<class T, class U> struct A {};

    template<template<class> class TT> auto f(TT<int> a) { return a; }
    // old-note@-1 2{{template template argument has different template parameters}}
    // new-note@-2 2{{substitution failure: too few template arguments}}

    A<int, float> v1;
    A<int, double> v2;

    using X = decltype(f(v1));
    // expected-error@-1 {{no matching function for call}}

    using X = decltype(f(v2));
    // expected-error@-1 {{no matching function for call}}
  } // namespace canon
  namespace expr {
    template <class T1, int E1> struct A {
      static constexpr auto val = E1;
    };
    template <template <class T3> class TT> void f(TT<int> v) {
      // old-note@-1 {{template template argument has different template parameters}}
      // new-note@-2 {{substitution failure: too few template arguments}}
      static_assert(v.val == 3);
    };
    void test() {
      f(A<int, 3>());
      // expected-error@-1 {{no matching function for call}}
    }
  } // namespace expr
  namespace packs {
    template <class T1, class ...T2s> struct A {
      static constexpr auto val = sizeof...(T2s);
    };

    template <template <class T3> class TT> void f(TT<int> v) {
      // old-note@-1 {{template template argument has different template parameters}}
      // new-note@-2 {{deduced type 'A<[...], (no argument), (no argument), (no argument)>' of 1st parameter does not match adjusted type 'A<[...], void, void, void>' of argument [with TT = A]}}
      static_assert(v.val == 3);
    };
    void test() {
      f(A<int, void, void, void>());
      // expected-error@-1 {{no matching function for call}}
    }
  } // namespace packs
  namespace nested {
    template <class T1, int V1, int V2> struct A {
      using type = T1;
      static constexpr int v1 = V1, v2 = V2;
    };

    template <template <class T1> class TT1> auto f(TT1<int>) {
      return TT1<float>();
    }

    template <template <class T2, int V3> class TT2> auto g(TT2<double, 1>) {
      // new-note@-1 {{too few template arguments for class template 'A'}}
      // old-note@-2 {{template template argument has different template parameters}}
      return f(TT2<int, 2>());
    }

    using B = decltype(g(A<double, 1, 3>()));
    // expected-error@-1 {{no matching function for call}}

    using X = B::type; // expected-error {{undeclared identifier 'B'}}
    using X = float;
    static_assert(B::v1 == 2); // expected-error {{undeclared identifier 'B'}}
    static_assert(B::v2 == 3); // expected-error {{undeclared identifier 'B'}}
  }
  namespace defaulted {
    template <class T1, class T2 = T1*> struct A {
      using type = T2;
    };

    template <template <class> class TT> TT<float> f(TT<int>);
    // new-note@-1  {{deduced type 'A<[...], (default) int *>' of 1st parameter does not match adjusted type 'A<[...], double *>' of argument [with TT = A]}}
    // old-note@-2 2{{template template argument has different template parameters}}

    using X = int*; // new-note {{previous definition is here}}
    using X = decltype(f(A<int>()))::type;
    // new-error@-1 {{different types ('decltype(f(A<int>()))::type' (aka 'float *') vs 'int *')}}
    // old-error@-2 {{no matching function for call}}

    using Y = double*;
    using Y = decltype(f(A<int, double*>()))::type;
    // expected-error@-1 {{no matching function for call}}
  } // namespace defaulted
} // namespace classes

namespace packs {
  namespace t1 {
    template<template<int, int...> class> struct A {};
    // new-error@-1 {{non-type parameter of template template parameter cannot be narrowed from type 'int' to 'char'}}
    // new-note@-2 {{previous template template parameter is here}}
    // old-note@-3 {{previous non-type template parameter with type 'int' is here}}

    template<char> struct B;
    // old-note@-1 {{template non-type parameter has a different type 'char' in template argument}}

    template struct A<B>;
    // new-note@-1 {{has different template parameters}}
    // old-error@-2 {{has different template parameters}}
  } // namespace t1
  namespace t2 {
    template<template<char, int...> class> struct A {};
    // old-note@-1 {{previous non-type template parameter with type 'char' is here}}

    template<int> struct B;
    // old-note@-1 {{template non-type parameter has a different type 'int' in template argument}}

    template struct A<B>;
    // old-error@-1 {{has different template parameters}}
  } // namespace t2
  namespace t3 {
    template<template<int...> class> struct A {};
    // new-error@-1 {{non-type parameter of template template parameter cannot be narrowed from type 'int' to 'char'}}
    // new-note@-2 {{previous template template parameter is here}}
    // old-note@-3 {{previous non-type template parameter with type 'int' is here}}

    template<char> struct B;
    // old-note@-1 {{template non-type parameter has a different type 'char' in template argument}}

    template struct A<B>;
    // new-note@-1 {{has different template parameters}}
    // old-error@-2 {{has different template parameters}}
  } // namespace t3
  namespace t4 {
    template<template<char...> class> struct A {};
    // old-note@-1 {{previous non-type template parameter with type 'char' is here}}

    template<int> struct B;
    // old-note@-1 {{template non-type parameter has a different type 'int' in template argument}}

    template struct A<B>;
    // old-error@-1 {{has different template parameters}}
  } // namespace t4
} // namespace packs

namespace fun_tmpl_call {
  namespace match_func {
    template <template <class> class TT> void f(TT<int>) {};
    // old-note@-1 {{has different template parameters}}
    template <class...> struct A {};
    void test() { f(A<int>()); }
    // old-error@-1 {{no matching function for call to 'f'}}
  } // namespace match_func
  namespace order_func_nonpack {
    template <template <class> class TT> void f(TT<int>) {}
    template <template <class...> class TT> void f(TT<int>) = delete;

    template <class> struct A {};
    void test() { f(A<int>()); }
  } // namespace order_func_nonpack
  namespace order_func_pack {
    template <template <class> class TT> void f(TT<int>) = delete;
    template <template <class...> class TT> void f(TT<int>) {}

    template <class...> struct A {};
    void test() { f(A<int>()); }
  } // namespace order_func_pack
  namespace match_enum {
    enum A {};
    template<template<A> class TT1> void f(TT1<{}>) {}
    // old-note@-1 {{invalid explicitly-specified argument}}
    template<int> struct B {};
    template void f<B>(B<{}>);
    // old-error@-1 {{does not refer to a function template}}
  } // namespace match_enum
  namespace match_method {
    struct A {
      template <template <class> class TT> void f(TT<int>) {};
      // old-note@-1 {{has different template parameters}}
    };
    template <class...> struct B {};
    void test() { A().f(B<int>()); }
    // old-error@-1 {{no matching member function for call to 'f'}}
  } // namespace match_method
  namespace order_method_nonpack {
    struct A {
      template <template <class> class TT> void f(TT<int>) {}
      template <template <class...> class TT> void f(TT<int>) = delete;
    };
    template <class> struct B {};
    void test() { A().f(B<int>()); }
  } // namespace order_method_nonpack
  namespace order_method_pack {
    struct A {
      template <template <class> class TT> void f(TT<int>) = delete;
      template <template <class...> class TT> void f(TT<int>) {}
    };
    template <class...> struct B {};
    void test() { A().f(B<int>()); }
  } // namespace order_method_pack
  namespace match_conv {
    struct A {
      template <template <class> class TT> operator TT<int>() { return {}; }
      // old-note@-1 {{different template parameters}}
    };
    template <class...> struct B {};
    // old-note@-1 2{{not viable}}
    void test() { B<int> b = A(); }
    // old-error@-1 {{no viable conversion from 'A' to 'B<int>'}}
  } // namespace match_conv
  namespace order_conv_nonpack {
    struct A {
      template <template <class> class TT> operator TT<int>() { return {}; };
      template <template <class...> class TT> operator TT<int>() = delete;
    };
    template <class> struct B {};
    void test() { B<int> b = A(); }
  } // namespace order_conv_nonpack
  namespace order_conv_pack {
    struct A {
      template <template <class> class TT> operator TT<int>() = delete;
      template <template <class...> class TT> operator TT<int>() { return {}; }
    };
    template <class...> struct B {};
    void test() { B<int> b = A(); }
  } // namespace order_conv_pack
  namespace regression1 {
    template <template <class, class...> class TT, class T1, class... T2s>
    void f(TT<T1, T2s...>) {}
    template <class> struct A {};
    void test() { f(A<int>()); }
  } // namespace regression1
} // namespace fun_tmpl_packs

namespace partial {
  namespace t1 {
    template<template<class... T1s> class TT1> struct A {};

    template<template<class T2> class TT2> struct A<TT2>;

    template<class... T3s> struct B;
    template struct A<B>;
  } // namespace t1
  namespace t2 {
    template<template<class... T1s> class TT1> struct A;

    template<template<class T2> class TT2> struct A<TT2> {};

    template<class T3> struct B;
    template struct A<B>;
  } // namespace t1

} // namespace partial

namespace regression1 {
  template <typename T, typename Y> struct map {};
  template <typename T> class foo {};

  template <template <typename...> class MapType, typename Value>
  Value bar(MapType<int, Value> map);

  template <template <typename...> class MapType, typename Value>
  Value bar(MapType<int, foo<Value>> map);

  void aux() {
    map<int, foo<int>> input;
    bar(input);
  }
} // namespace regression1

namespace constraints {
  template <class T> concept C1 = true;
  // new-note@-1 {{similar constraint expression here}}
  // new-note@-2 2{{similar constraint expressions not considered equivalent}}

  template <class T> concept C2 = C1<T> && true;
  // new-note@-1 2{{similar constraint expression here}}

  template <class T> concept D1 = true;
  // new-note@-1 {{similar constraint expressions not considered equivalent}}

  namespace t1 {
    template<template<C1, class... T1s> class TT1> // new-note {{TT1' declared here}}
    struct A {};
    template<D1, class T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t1
  namespace t2 {
    template<template<C2, class... T1s> class TT1> struct A {};
    template<C1, class T2> struct B {};
    template struct A<B>;
  } // namespace t2
  namespace t3 {
    template<template<C1, class... T1s> class TT1> // new-note {{'TT1' declared here}}
    struct A {};
    template<C2, class T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t2
  namespace t4 {
    // FIXME: This should be accepted.
    template<template<C1... T1s> class TT1> // new-note {{'TT1' declared here}}
    struct A {};
    template<C1 T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t4
  namespace t5 {
    // FIXME: This should be accepted
    template<template<C2... T1s> class TT1> // new-note {{'TT1' declared here}}
    struct A {};
    template<C1 T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t5
  namespace t6 {
    template<template<C1... T1s> class TT1> // new-note {{'TT1' declared here}}
    struct A {};
    template<C2 T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t6
  namespace t7 {
    template<template<class... T1s> class TT1>
    struct A {};
    template<C1 T2> struct B {};
    template struct A<B>;
  } // namespace t7
  namespace t8 {
    template<template<C1... T1s> class TT1>
    struct A {};
    template<class T2> struct B {};
    template struct A<B>;
  } // namespace t8
  namespace t9 {
    template<template<C1... T1s> class TT1> // new-note {{'TT1' declared here}}
    struct A {};
    template<D1 T2> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t9
  namespace t10 {
    template<template<class...> requires C1<int> class TT1> // new-note {{'TT1' declared here}}
    struct A {};

    template<class> requires C2<int> struct B {}; // new-note {{'B' declared here}}
    template struct A<B>;
    // new-error@-1 {{'B' is more constrained than template template parameter 'TT1'}}
  } // namespace t10
  namespace t11 {
    template<template<class...> requires C2<int> class TT1> struct A {};
    template<class> requires C1<int> struct B {};
    template struct A<B>;
  } // namespace t11
} // namespace constraints

namespace regression2 {
  template <class> struct D {};

  template <class ET, template <class> class VT>
  struct D<VT<ET>>;

  template <typename, int> struct Matrix;
  template struct D<Matrix<double, 3>>;
} // namespace regression2
namespace regression3 {
  struct None {};
  template<class T> struct Node { using type = T; };

  template <template<class> class TT, class T>
  // old-note@-1 {{previous template type parameter declared here}}
  struct A {
    static_assert(!__is_same(T, None));
    using type2 = typename A<TT, typename T::type>::type2;
  };

  template <template<class> class TT> struct A<TT, None> {
    using type2 = void;
  };

  template <class...> class B {};
  // old-note@-1 {{template type parameter pack does not match template type parameter}}
  template struct A<B, Node<None>>;
  // old-error@-1 {{different template}}
} // namespace regression3
namespace GH130362 {
  template <template <template <class... T1> class TT1> class TT2> struct A {};
  template <template <class U1> class UU1> struct B {};
  template struct A<B>;
} // namespace GH130362

namespace nttp_auto {
  namespace t1 {
    template <template <auto... Va> class TT> struct A {};
    template <int Vi, short Vs> struct B;
    template struct A<B>;
  } // namespace t1
  namespace t2 {
    template<template<auto... Va1, auto Va2> class> struct A {};
    // expected-error@-1 {{template parameter pack must be the last template parameter}}
    // old-note@-2 {{previous template template parameter is here}}
    template<int... Vi> struct B;
    // old-note@-1 {{too few template parameters}}
    template struct A<B>;
    // old-error@-1 {{different template parameters}}
  } // namespace t2
  namespace t3 {
    template<template<auto... Va1, auto... Va2> class> struct A {};
    // expected-error@-1 {{template parameter pack must be the last template parameter}}
    template<int... Vi> struct B;
    template struct A<B>;
  } // namespace t3
} // namespace nttp_auto

namespace nttp_partial_order {
  namespace t1 {
    template<template<short> class TT1> void f(TT1<0>);
    template<template<int>   class TT2> void f(TT2<0>) {}
    template<int> struct B {};
    template void f<B>(B<0>);
  } // namespace t1
  namespace t2 {
    struct A {} a;
    template<template<A&>       class TT1> void f(TT1<a>);
    template<template<const A&> class TT2> void f(TT2<a>) {}
    template<const A&> struct B {};
    template void f<B>(B<a>);
  } // namespace t2
  namespace t3 {
    enum A {};
    template<template<A>   class TT1> void f(TT1<{}>);
    template<template<int> class TT2> void f(TT2<{}>) {}
    template<int> struct B {};
    template void f<B>(B<{}>);
  } // namespace t3
  namespace t4 {
    struct A {} a;
    template<template<A*>       class TT1> void f(TT1<&a>);
    template<template<const A*> class TT2> void f(TT2<&a>) {}
    template<const A*> struct B {};
    template void f<B>(B<&a>);
  } // namespace t4
  namespace t5 {
    struct A { int m; };
    template<template<int A::*>       class TT1> void f(TT1<&A::m>);
    template<template<const int A::*> class TT2> void f(TT2<&A::m>) {}
    template<const int A::*> struct B {};
    template void f<B>(B<&A::m>);
  } // namespace t5
  namespace t6 {
    struct A {};
    using nullptr_t = decltype(nullptr);
    template<template<nullptr_t> class TT2> void f(TT2<nullptr>);
    template<template<A*>        class TT1> void f(TT1<nullptr>) {}
    template<A*> struct B {};
    template void f<B>(B<nullptr>);
  } // namespace t6
} // namespace nttp_partial_order