src/third_party/llvm-project/clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.type/p9-0x.cpp

// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s

template<typename ...Types> struct tuple;
template<unsigned> struct unsigned_c;

template<typename T, typename U> 
struct is_same {
  static const bool value = false;
};

template<typename T>
struct is_same<T, T> {
  static const bool value = true;
};

namespace PackExpansionNotAtEnd {
  template<typename T, typename U>
  struct tuple_same_with_int {
    static const bool value = false;
  };

  template<typename ...Types>
  struct tuple_same_with_int<tuple<Types...>, tuple<Types..., int>> {
    static const bool value = true;
  };

  int tuple_same_with_int_1[tuple_same_with_int<tuple<int, float, double>,
                                                tuple<int, float, double, int>
                                                >::value? 1 : -1];

  template<typename ... Types> struct UselessPartialSpec;

  template<typename ... Types, // expected-note{{non-deducible template parameter 'Types'}}
           typename Tail> // expected-note{{non-deducible template parameter 'Tail'}}
  struct UselessPartialSpec<Types..., Tail>; // expected-error{{class template partial specialization contains template parameters that cannot be deduced; this partial specialization will never be used}}
}

// When a pack expansion occurs within a template argument list, the entire
// list is a non-deduced context. For the corresponding case in a function
// parameter list, only that parameter is non-deduced.
//
// FIXME: It's not clear that this difference is intended, but the wording is
// explicit.
namespace PackExpansionNotAtEndFunctionVersusTemplate {
  template<typename ...T> struct X {};
  template<typename ...T, typename U> void f1(void(T..., U));
  // expected-note@+1 {{couldn't infer template argument 'U'}}
  template<typename ...T, typename U> void f2(X<T..., U>); // FIXME: ill-formed, U is not deducible

  void g(int, int, int);
  X<int, int, int> h;
  void test() {
    // This is deducible: the T... parameter is a non-deduced context, but
    // that's OK because we don't need to deduce it.
    f1<int, int>(g);
    // This is not deducible: the T... parameter renders the entire
    // template-argument-list a non-deduced context, so U is not deducible.
    f2<int, int>(h); // expected-error {{no matching function}}
  }

  template<typename T> struct Y;
  template<typename ...T, // expected-note {{non-deducible template parameter 'T'}}
           typename U>
    struct Y<void(T..., U)> {}; // expected-error {{cannot be deduced}}
  template<typename ...T, // expected-note {{non-deducible template parameter 'T'}}
           typename U> // expected-note {{non-deducible template parameter 'U'}}
    struct Y<X<T..., U>>; // expected-error {{cannot be deduced}}
  // FIXME: T is not deducible here, due to [temp.deduct.call]p1:
  //   "When a function parameter pack appears in a non-deduced context,
  //   the type of that pack is never deduced."
  template<typename ...T,
           typename U>
    struct Y<void(T..., U, T...)> {};
}

namespace DeduceNonTypeTemplateArgsInArray {
  template<typename ...ArrayTypes>
  struct split_arrays;

  template<typename ...ElementTypes, unsigned ...Bounds>
  struct split_arrays<ElementTypes[Bounds]...> {
    typedef tuple<ElementTypes...> element_types;

    // FIXME: Would like to have unsigned_tuple<Bounds...> here.
    typedef tuple<unsigned_c<Bounds>...> bounds_types;
  };

  int check1[is_same<split_arrays<int[1], float[2], double[3]>::element_types,
                     tuple<int, float, double>>::value? 1 : -1];
  int check2[is_same<split_arrays<int[1], float[2], double[3]>::bounds_types,
                     tuple<unsigned_c<1>, unsigned_c<2>, unsigned_c<3>>
                     >::value? 1 : -1];
}

namespace DeduceWithDefaultArgs {
  template<template<typename...> class Container> void f(Container<int>); // expected-note {{deduced type 'X<[...], (default) int>' of 1st parameter does not match adjusted type 'X<[...], double>' of argument [with Container = X]}}
  template<typename, typename = int> struct X {};
  void g() {
    // OK, use default argument for the second template parameter.
    f(X<int>{});
    f(X<int, int>{});

    // Not OK.
    f(X<int, double>{}); // expected-error {{no matching function for call to 'f'}}
  }
}