clang/test/Parser/cxx1z-fold-expressions.cpp

   1 // RUN: %clang_cc1 -std=c++1z -verify %s
   2
   3 template<typename ...T> constexpr auto sum(T ...t) { return (... + t); }
   4 template<typename ...T> constexpr auto product(T ...t) { return (t * ...); }
   5 template<typename ...T> constexpr auto all(T ...t) { return (true && ... && t); }
   6 template<typename ...T> constexpr auto all2(T ...t) { return (t && ... && true); }
   7
   8 int k1 = (1 + ... + 2); // expected-error {{does not contain any unexpanded parameter packs}}
   9 int k2 = (1 + ...); // expected-error {{does not contain any unexpanded parameter packs}}
  10 int k3 = (... + 2); // expected-error {{does not contain any unexpanded parameter packs}}
  11
  12 struct A { A(int); friend A operator+(A, A); A operator-(A); A operator()(A); A operator[](A); };
  13 A operator*(A, A);
  14
  15 template<int ...N> void bad1() { (N + ... + N); } // expected-error {{unexpanded parameter packs in both operands}}
  16 // FIXME: it would be reasonable to support this as an extension.
  17 template<int ...N> void bad2() { (2 * N + ... + 1); } // expected-error {{expression not permitted as operand}}
  18 template<int ...N> void bad3() { (2 + N * ... * 1); } // expected-error {{expression not permitted as operand}}
  19 template<int ...N, int ...M> void bad4(int (&...x)[N]) { (N + M * ... * 1); } // expected-error {{expression not permitted as operand}}
  20 template<int ...N, int ...M> void fixed4(int (&...x)[N]) { ((N + M) * ... * 1); }
  21 template<typename ...T> void bad4a(T ...t) { (t * 2 + ... + 1); } // expected-error {{expression not permitted as operand}}
  22 template<int ...N> void bad4b() { (A(0) + A(N) + ...); } // expected-error {{expression not permitted as operand}}
  23 template<int ...N> void bad4c() { (A(0) - A(N) + ...); } // expected-error {{expression not permitted as operand}}
  24 template<int ...N> void bad4d() { (A(0)(A(0)) + ... + A(0)[A(N)]); }
  25
  26 // Parens are mandatory.
  27 template<int ...N> void bad5() { N + ...; } // expected-error {{expected expression}} expected-error +{{}}
  28 template<int ...N> void bad6() { ... + N; } // expected-error {{expected expression}}
  29 template<int ...N> void bad7() { N + ... + N; } // expected-error {{expected expression}} expected-error +{{}}
  30
  31 // Must have a fold-operator in the relevant places.
  32 template<int ...N> int bad8() { return (N + ... * 3); } // expected-error {{operators in fold expression must be the same}}
  33 template<int ...N> int bad9() { return (3 + ... * N); } // expected-error {{operators in fold expression must be the same}}
  34 template<int ...N> int bad10() { return (3 ? ... : N); } // expected-error +{{}} expected-note {{to match}}
  35 template<int ...N> int bad11() { return (N + ... 0); } // expected-error {{expected a foldable binary operator}} expected-error {{expected expression}}
  36 template<int ...N> int bad12() { return (... N); } // expected-error {{expected expression}}
  37
  38 template<typename ...T> void as_operand_of_cast(int a, T ...t) {
  39   return
  40     (int)(a + ... + undeclared_junk) + // expected-error {{undeclared}} expected-error {{does not contain any unexpanded}}
  41     (int)(t + ... + undeclared_junk) + // expected-error {{undeclared}}
  42     (int)(... + undeclared_junk) + // expected-error {{undeclared}} expected-error {{does not contain any unexpanded}}
  43     (int)(undeclared_junk + ...) + // expected-error {{undeclared}}
  44     (int)(a + ...) + // expected-error {{does not contain any unexpanded}}
  45     (int)(a, ...) + // expected-error {{does not contain any unexpanded}}
  46     (int)(..., a) + // expected-error {{does not contain any unexpanded}}
  47     (int)(a, ..., undeclared_junk) + // expected-error {{undeclared}} expected-error {{does not contain any unexpanded}}
  48     (int)(t, ...) +
  49     (int)(..., t) +
  50     (int)(t, ..., a);
  51 }
  52
  53 // fold-operator can be '>' or '>>'.
  54 template <int... N> constexpr bool greaterThan() { return (N > ...); }
  55 template <int... N> constexpr int rightShift() { return (N >> ...); }
  56
  57 static_assert(greaterThan<2, 1>());
  58 static_assert(rightShift<10, 1>() == 5);
  59
  60 template <auto V> constexpr auto Identity = V;
  61
  62 // Support fold operators within templates.
  63 template <int... N> constexpr int nestedFoldOperator() {
  64   return Identity<(Identity<0> >> ... >> N)> +
  65     Identity<(N >> ... >> Identity<0>)>;
  66 }
  67
  68 static_assert(nestedFoldOperator<3, 1>() == 1);
  69
  70 // A fold-expression is a primary-expression.
  71 template <typename T, typename... Ts>
  72 constexpr auto castSum(Ts... Args) {
  73   return (T)(Args + ...).Value; // expected-error{{member reference base type 'int' is not a structure or union}}
  74 }
  75
  76 template <typename... Ts>
  77 constexpr auto simpleSum(Ts... Args) {
  78   return (... + Args).Value; // expected-error{{member reference base type 'int' is not a structure or union}}
  79 }
  80
  81 void prim() {
  82   castSum<int>(1, 2);
  83   // expected-note@-1{{in instantiation of function template specialization}}
  84   simpleSum(1, 2);
  85   // expected-note@-1{{in instantiation of function template specialization}}
  86
  87   struct Number {
  88     int Value;
  89     constexpr Number operator+(Number Rhs) const { return {Rhs.Value + Value}; }
  90   };
  91
  92   static_assert(castSum<long>(Number{1}, Number{2}) == 3);
  93   static_assert(simpleSum(Number{1}, Number{2}) == 3);
  94 }