clang/test/CXX/expr/expr.const/p6-2a.cpp

   1 // RUN: %clang_cc1 -std=c++2a -verify %s
   2
   3 constexpr int non_class = 42;
   4 constexpr int arr_non_class[5] = {1, 2, 3};
   5
   6 struct A {
   7   int member = 1;
   8   constexpr ~A() { member = member + 1; }
   9 };
  10 constexpr A class_ = {};
  11 constexpr A arr_class[5] = {{}, {}};
  12
  13 struct Mutable {
  14   mutable int member = 1; // expected-note {{declared here}}
  15   constexpr ~Mutable() { member = member + 1; } // expected-note {{read of mutable member}}
  16 };
  17 constexpr Mutable mut_member; // expected-error {{must have constant destruction}} expected-note {{in call}}
  18
  19 struct MutableStore {
  20   mutable int member = 1; // expected-note {{declared here}}
  21   constexpr ~MutableStore() { member = 2; } // expected-note {{assignment to mutable member}}
  22 };
  23 constexpr MutableStore mut_store; // expected-error {{must have constant destruction}} expected-note {{in call}}
  24
  25 // Note: the constant destruction rules disallow this example even though hcm.n is a const object.
  26 struct MutableConst {
  27   struct HasConstMember {
  28     const int n = 4;
  29   };
  30   mutable HasConstMember hcm; // expected-note {{here}}
  31   constexpr ~MutableConst() {
  32     int q = hcm.n; // expected-note {{read of mutable}}
  33   }
  34 };
  35 constexpr MutableConst mc; // expected-error {{must have constant destruction}} expected-note {{in call}}
  36
  37 struct Temporary {
  38   int &&temp;
  39   constexpr ~Temporary() {
  40     int n = temp; // expected-note {{outside the expression that created the temporary}}
  41   }
  42 };
  43 constexpr Temporary t = {3}; // expected-error {{must have constant destruction}} expected-note {{created here}} expected-note {{in call}}
  44
  45 namespace P1073R3 {
  46 consteval int f() { return 42; } // expected-note 2 {{declared here}}
  47 consteval auto g() { return f; }
  48 consteval int h(int (*p)() = g()) { return p(); }
  49 constexpr int r = h();
  50 constexpr auto e = g();  // expected-error {{call to consteval function 'P1073R3::g' is not a constant expression}} \
  51                             expected-error {{constexpr variable 'e' must be initialized by a constant expression}} \
  52                             expected-note 2 {{pointer to a consteval declaration is not a constant expression}}
  53 static_assert(r == 42);
  54 } // namespace P1073R3