clang/test/SemaCXX/decomposed-condition.cpp

   1 // RUN: %clang_cc1 -std=c++1z -Wno-binding-in-condition -verify %s
   2
   3 struct X {
   4   bool flag;
   5   int data;
   6   constexpr explicit operator bool() const {
   7     return flag;
   8   }
   9   constexpr operator int() const {
  10     return data;
  11   }
  12 };
  13
  14 namespace CondInIf {
  15 constexpr int f(X x) {
  16   if (auto [ok, d] = x)
  17     return d + int(ok);
  18   else
  19     return d * int(ok);
  20   ok = {}; // expected-error {{use of undeclared identifier 'ok'}}
  21   d = {};  // expected-error {{use of undeclared identifier 'd'}}
  22 }
  23
  24 static_assert(f({true, 2}) == 3);
  25 static_assert(f({false, 2}) == 0);
  26
  27 constexpr char g(char const (&x)[2]) {
  28   if (auto &[a, b] = x)
  29     return a;
  30   else
  31     return b;
  32
  33   if (auto [a, b] = x) // expected-error {{an array type is not allowed here}}
  34     ;
  35 }
  36
  37 static_assert(g("x") == 'x');
  38 } // namespace CondInIf
  39
  40 namespace CondInSwitch {
  41 constexpr int f(int n) {
  42   switch (X s = {true, n}; auto [ok, d] = s) {
  43     s = {};
  44   case 0:
  45     return int(ok);
  46   case 1:
  47     return d * 10;
  48   case 2:
  49     return d * 40;
  50   default:
  51     return 0;
  52   }
  53   ok = {}; // expected-error {{use of undeclared identifier 'ok'}}
  54   d = {};  // expected-error {{use of undeclared identifier 'd'}}
  55   s = {};  // expected-error {{use of undeclared identifier 's'}}
  56 }
  57
  58 static_assert(f(0) == 1);
  59 static_assert(f(1) == 10);
  60 static_assert(f(2) == 80);
  61 } // namespace CondInSwitch
  62
  63 namespace CondInWhile {
  64 constexpr int f(int n) {
  65   int m = 1;
  66   while (auto [ok, d] = X{n > 1, n}) {
  67     m *= d;
  68     --n;
  69   }
  70   return m;
  71   return ok; // expected-error {{use of undeclared identifier 'ok'}}
  72 }
  73
  74 static_assert(f(0) == 1);
  75 static_assert(f(1) == 1);
  76 static_assert(f(4) == 24);
  77 } // namespace CondInWhile
  78
  79 namespace CondInFor {
  80 constexpr int f(int n) {
  81   int a = 1, b = 1;
  82   for (X x = {true, n}; auto &[ok, d] = x; --d) {
  83     if (d < 2)
  84       ok = false;
  85     else {
  86       int x = b;
  87       b += a;
  88       a = x;
  89     }
  90   }
  91   return b;
  92   return d; // expected-error {{use of undeclared identifier 'd'}}
  93 }
  94
  95 static_assert(f(0) == 1);
  96 static_assert(f(1) == 1);
  97 static_assert(f(2) == 2);
  98 static_assert(f(5) == 8);
  99 } // namespace CondInFor