--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/SemaTemplate/alias-templates.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,267 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+template<typename S>
+struct A {
+  typedef S B;
+  template<typename T> using C = typename T::B;
+  template<typename T> struct D {
+    template<typename U> using E = typename A<U>::template C<A<T>>;
+    template<typename U> using F = A<E<U>>;
+    template<typename U> using G = C<F<U>>;
+    G<T> g;
+  };
+  typedef decltype(D<B>().g) H;
+  D<H> h;
+  template<typename T> using I = A<decltype(h.g)>;
+  template<typename T> using J = typename A<decltype(h.g)>::template C<I<T>>;
+};
+
+A<int> a;
+A<char>::D<double> b;
+
+template<typename T> T make();
+
+namespace X {
+  template<typename T> struct traits {
+    typedef T thing;
+    typedef decltype(val(make<thing>())) inner_ptr;
+
+    template<typename U> using rebind_thing = typename thing::template rebind<U>;
+    template<typename U> using rebind = traits<rebind_thing<U>>;
+
+    inner_ptr &&alloc();
+    void free(inner_ptr&&);
+  };
+
+  template<typename T> struct ptr_traits {
+    typedef T *type;
+  };
+  template<typename T> using ptr = typename ptr_traits<T>::type;
+
+  template<typename T> struct thing {
+    typedef T inner;
+    typedef ptr<inner> inner_ptr;
+    typedef traits<thing<inner>> traits_type;
+
+    template<typename U> using rebind = thing<U>;
+
+    thing(traits_type &traits) : traits(traits), val(traits.alloc()) {}
+    ~thing() { traits.free(static_cast<inner_ptr&&>(val)); }
+
+    traits_type &traits;
+    inner_ptr val;
+
+    friend inner_ptr val(const thing &t) { return t.val; }
+  };
+
+  template<> struct ptr_traits<bool> {
+    typedef bool &type;
+  };
+  template<> bool &traits<thing<bool>>::alloc() { static bool b; return b; }
+  template<> void traits<thing<bool>>::free(bool&) {}
+}
+
+typedef X::traits<X::thing<int>> itt;
+
+itt::thing::traits_type itr;
+itt::thing ith(itr);
+
+itt::rebind<bool> btr;
+itt::rebind_thing<bool> btt(btr);
+
+namespace PR11848 {
+  template<typename T> using U = int;
+
+  template<typename T, typename ...Ts>
+  void f1(U<T> i, U<Ts> ...is) { // expected-note 2{{couldn't infer template argument 'T'}}
+    return i + f1<Ts...>(is...);
+  }
+
+  template<typename ...Ts>
+  void f2(U<Ts> ...is) { } // expected-note {{deduced incomplete pack <(no value)> for template parameter 'Ts'}}
+
+  template<typename...> struct type_tuple {};
+  template<typename ...Ts>
+  void f3(type_tuple<Ts...>, U<Ts> ...is) {} // expected-note {{deduced packs of different lengths for parameter 'Ts' (<void, void, void> vs. <(no value), (no value)>)}}
+
+  void g() {
+    f1(U<void>()); // expected-error {{no match}}
+    f1(1, 2, 3, 4, 5); // expected-error {{no match}}
+    f2(); // ok
+    f2(1); // expected-error {{no match}}
+    f3(type_tuple<>());
+    f3(type_tuple<void, void, void>(), 1, 2); // expected-error {{no match}}
+    f3(type_tuple<void, void, void>(), 1, 2, 3);
+  }
+
+  template<typename ...Ts>
+  struct S {
+    S(U<Ts>...ts);
+  };
+
+  template<typename T>
+  struct Hidden1 {
+    template<typename ...Ts>
+    Hidden1(typename T::template U<Ts> ...ts);
+  };
+
+  template<typename T, typename ...Ts>
+  struct Hidden2 {
+    Hidden2(typename T::template U<Ts> ...ts);
+  };
+
+  struct Hide {
+    template<typename T> using U = int;
+  };
+
+  Hidden1<Hide> h1;
+  Hidden2<Hide, double, char> h2(1, 2);
+}
+
+namespace Core22036 {
+  struct X {};
+  void h(...);
+  template<typename T> using Y = X;
+  template<typename T, typename ...Ts> struct S {
+    // An expression can contain an unexpanded pack without being type or
+    // value dependent. This is true even if the expression's type is a pack
+    // expansion type.
+    void f1(Y<T> a) { h(g(a)); } // expected-error {{undeclared identifier 'g'}}
+    void f2(Y<Ts>...as) { h(g(as)...); } // expected-error {{undeclared identifier 'g'}}
+    void f3(Y<Ts>...as) { g(as...); } // ok
+    void f4(Ts ...ts) { h(g(sizeof(ts))...); } // expected-error {{undeclared identifier 'g'}}
+    // FIXME: We can reject this, since it has no valid instantiations because
+    // 'g' never has any associated namespaces.
+    void f5(Ts ...ts) { g(sizeof(ts)...); } // ok
+  };
+}
+
+namespace PR13243 {
+  template<typename A> struct X {};
+  template<int I> struct C {};
+  template<int I> using Ci = C<I>;
+
+  template<typename A, int I> void f(X<A>, Ci<I>) {}
+  template void f(X<int>, C<0>);
+}
+
+namespace PR13136 {
+  template <typename T, T... Numbers>
+  struct NumberTuple { };
+
+  template <unsigned int... Numbers>
+  using MyNumberTuple = NumberTuple<unsigned int, Numbers...>;
+
+  template <typename U, unsigned int... Numbers>
+  void foo(U&&, MyNumberTuple<Numbers...>);
+
+  template <typename U, unsigned int... Numbers>
+  void bar(U&&, NumberTuple<unsigned int, Numbers...>);
+
+  int main() {
+    foo(1, NumberTuple<unsigned int, 0, 1>());
+    bar(1, NumberTuple<unsigned int, 0, 1>());
+    return 0;
+  }
+}
+
+namespace PR16646 {
+  namespace test1 {
+    template <typename T> struct DefaultValue { const T value=0;};
+    template <typename ... Args> struct tuple {};
+    template <typename ... Args> using Zero = tuple<DefaultValue<Args> ...>;
+    template <typename ... Args> void f(const Zero<Args ...> &t);
+    void f() {
+        f(Zero<int,double,double>());
+    }
+  }
+
+  namespace test2 {
+    template<int x> struct X {};
+    template <template<int x> class temp> struct DefaultValue { const temp<0> value; };
+    template <typename ... Args> struct tuple {};
+    template <template<int x> class... Args> using Zero = tuple<DefaultValue<Args> ...>;
+    template <template<int x> class... Args> void f(const Zero<Args ...> &t);
+    void f() {
+      f(Zero<X,X,X>());
+    }
+  }
+}
+
+namespace PR16904 {
+  template <typename,typename>
+  struct base {
+    template <typename> struct derived;
+  };
+  // FIXME: The diagnostics here are terrible.
+  template <typename T, typename U, typename V>
+  using derived = base<T, U>::template derived<V>; // expected-error {{expected a type}} expected-error {{expected ';'}}
+  template <typename T, typename U, typename V>
+  using derived2 = ::PR16904::base<T, U>::template derived<V>; // expected-error {{expected a type}} expected-error {{expected ';'}}
+}
+
+namespace PR14858 {
+  template<typename ...T> using X = int[sizeof...(T)];
+
+  template<typename ...U> struct Y {
+    using Z = X<U...>;
+  };
+  using A = Y<int, int, int, int>::Z;
+  using A = int[4];
+
+  // FIXME: These should be treated as being redeclarations.
+  template<typename ...T> void f(X<T...> &) {}
+  template<typename ...T> void f(int(&)[sizeof...(T)]) {}
+
+  template<typename ...T> void g(X<typename T::type...> &) {}
+  template<typename ...T> void g(int(&)[sizeof...(T)]) {} // ok, different
+
+  template<typename ...T, typename ...U> void h(X<T...> &) {}
+  template<typename ...T, typename ...U> void h(X<U...> &) {} // ok, different
+
+  template<typename ...T> void i(auto (T ...t) -> int(&)[sizeof...(t)]);
+  auto mk_arr(int, int) -> int(&)[2];
+  void test_i() { i<int, int>(mk_arr); }
+
+#if 0 // FIXME: This causes clang to assert.
+  template<typename ...T> using Z = auto (T ...p) -> int (&)[sizeof...(p)];
+  template<typename ...T, typename ...U> void j(Z<T..., U...> &) {}
+  void test_j() { j<int, int>(mk_arr); }
+#endif
+
+  template<typename ...T> struct Q {
+    template<typename ...U> using V = int[sizeof...(U)];
+    template<typename ...U> void f(V<typename U::type..., typename T::type...> *);
+  };
+  struct B { typedef int type; };
+  void test_q(int (&a)[5]) { Q<B, B, B>().f<B, B>(&a); }
+}
+
+namespace redecl {
+  template<typename> using A = int;
+  template<typename = void> using A = int;
+  A<> a; // ok
+}
+
+namespace PR31514 {
+  template<typename T, typename> using EnableTupleSize = T;
+
+  template<typename T> struct tuple_size { static const int value = 0; };
+  template<typename T> struct tuple_size<EnableTupleSize<const T, decltype(tuple_size<T>::value)>> {};
+  template<typename T> struct tuple_size<EnableTupleSize<volatile T, decltype(tuple_size<T>::value)>> {};
+
+  tuple_size<const int> t;
+}
+
+namespace an_alias_template_is_not_a_class_template {
+  template<typename T> using Foo = int; // expected-note 3{{here}}
+  Foo x; // expected-error {{use of alias template 'Foo' requires template arguments}}
+  Foo<> y; // expected-error {{too few template arguments for alias template 'Foo'}}
+  int z = Foo(); // expected-error {{use of alias template 'Foo' requires template arguments}}
+
+  template<template<typename> class Bar> void f() { // expected-note 3{{here}}
+    Bar x; // expected-error {{use of template template parameter 'Bar' requires template arguments}}
+    Bar<> y; // expected-error {{too few template arguments for template template parameter 'Bar'}}
+    int z = Bar(); // expected-error {{use of template template parameter 'Bar' requires template arguments}}
+  }
+}