clang/test/Parser/cxx2c-variadic-friends.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c %s
   2
   3 template <typename> struct TS; // #template
   4
   5 struct Errors {
   6   friend int, int;
   7   friend int, long, char;
   8
   9   // We simply diagnose and ignore the '...' here.
  10   friend float...; // expected-error {{pack expansion does not contain any unexpanded parameter packs}}
  11
  12   friend short..., unsigned, unsigned short...; // expected-error 2 {{pack expansion does not contain any unexpanded parameter packs}}
  13
  14   template <typename>
  15   friend struct TS, int; // expected-error {{a friend declaration that befriends a template must contain exactly one type-specifier}}
  16
  17   double friend; // expected-error {{'friend' must appear first in a non-function declaration}}
  18   double friend, double; // expected-error {{expected member name or ';' after declaration specifiers}}
  19 };
  20
  21 template <typename>
  22 struct C { template<class T> class Nested; };
  23
  24 template <typename, typename>
  25 struct D { template<class T> class Nested; };
  26
  27 template <bool>
  28 struct E { template<class T> class Nested; };
  29
  30 template<class... Ts> // expected-note {{template parameter is declared here}}
  31 struct VS {
  32   friend Ts...;
  33
  34   friend class Ts...; // expected-error {{declaration of 'Ts' shadows template parameter}}
  35   // expected-error@-1 {{pack expansion does not contain any unexpanded parameter packs}}
  36
  37   // TODO: Fix-it hint to insert '...'.
  38   friend Ts; // expected-error {{friend declaration contains unexpanded parameter pack}}
  39
  40   template<class... Us>
  41   friend Us...; // expected-error {{friend type templates must use an elaborated type}}
  42
  43   template<class... Us> // expected-note {{is declared here}}
  44   friend class Us...; // expected-error {{declaration of 'Us' shadows template parameter}}
  45
  46   template<class U>
  47   friend class C<Ts>::template Nested<U>...; // expected-error {{cannot specialize a dependent template}}
  48
  49   template<class... Us>
  50   friend class C<Ts...>::template Nested<Us>...; // expected-error {{cannot specialize a dependent template}}
  51
  52   // Nonsense (see CWG 2917).
  53   template<class... Us>
  54   friend class C<Us>::Nested...; // expected-error {{friend declaration expands pack 'Us' that is declared it its own template parameter list}}
  55
  56   template<bool... Bs>
  57   friend class E<Bs>::Nested...; // expected-error {{friend declaration expands pack 'Bs' that is declared it its own template parameter list}}
  58
  59   // FIXME: Both of these should be valid, but we can't handle these at
  60   // the moment because the NNS is dependent.
  61   template<class ...T>
  62   friend class TS<Ts>::Nested...; // expected-warning {{dependent nested name specifier 'TS<Ts>::' for friend template declaration is not supported; ignoring this friend declaration}}
  63
  64   template<class T>
  65   friend class D<T, Ts>::Nested...; // expected-warning {{dependent nested name specifier 'D<T, Ts>::' for friend class declaration is not supported; turning off access control for 'VS'}}
  66 };
  67
  68 namespace length_mismatch {
  69 struct A {
  70   template <typename...>
  71   struct Nested {
  72     struct Foo{};
  73   };
  74 };
  75 template <typename ...Ts>
  76 struct S {
  77   template <typename ...Us>
  78   struct T {
  79     // expected-error@+2 {{pack expansion contains parameter packs 'Ts' and 'Us' that have different lengths (1 vs. 2)}}
  80     // expected-error@+1 {{pack expansion contains parameter packs 'Ts' and 'Us' that have different lengths (2 vs. 1)}}
  81     friend class Ts::template Nested<Us>::Foo...;
  82   };
  83 };
  84
  85 void f() {
  86   S<A>::T<int> s;
  87   S<A, A>::T<int, long> s2;
  88   S<A>::T<int, long> s3; // expected-note {{in instantiation of}}
  89   S<A, A>::T<int> s4; // expected-note {{in instantiation of}}
  90 }
  91 }