clang/test/CXX/expr/expr.const/p6.cpp

   1 // RUN: %clang_cc1 -std=c++17 -verify %s
   2
   3 template<typename T> int not_constexpr() { return T::error; }
   4 template<typename T> constexpr int is_constexpr() { return T::error; } // expected-error {{'::'}}
   5
   6 template<typename T> int not_constexpr_var = T::error;
   7 template<typename T> constexpr int is_constexpr_var = T::error; // expected-error {{'::'}}
   8 template<typename T> const int is_const_var = T::error; // expected-error {{'::'}}
   9 template<typename T> const volatile int is_const_volatile_var = T::error;
  10 template<typename T> T is_dependent_var = T::error; // expected-error {{'::'}}
  11 template<typename T> int &is_reference_var = T::error; // expected-error {{'::'}}
  12 template<typename T> float is_float_var = T::error;
  13
  14 void test() {
  15   // Do not instantiate functions referenced in unevaluated operands...
  16   (void)sizeof(not_constexpr<long>());
  17   (void)sizeof(is_constexpr<long>());
  18   (void)sizeof(not_constexpr_var<long>);
  19   (void)sizeof(is_constexpr_var<long>);
  20   (void)sizeof(is_const_var<long>);
  21   (void)sizeof(is_const_volatile_var<long>);
  22   (void)sizeof(is_dependent_var<long>);
  23   (void)sizeof(is_dependent_var<const long>);
  24   (void)sizeof(is_reference_var<long>);
  25   (void)sizeof(is_float_var<long>);
  26
  27   // ... but do if they are potentially constant evaluated, and refer to
  28   // constexpr functions or to variables usable in constant expressions.
  29   (void)sizeof(int{not_constexpr<int>()});
  30   (void)sizeof(int{is_constexpr<int>()}); // expected-note {{instantiation of}}
  31   (void)sizeof(int{not_constexpr_var<int>});
  32   (void)sizeof(int{is_constexpr_var<int>}); // expected-note {{instantiation of}}
  33   (void)sizeof(int{is_const_var<int>}); // expected-note {{instantiation of}}
  34   (void)sizeof(int{is_const_volatile_var<int>});
  35   (void)sizeof(int{is_dependent_var<int>});
  36   (void)sizeof(int{is_dependent_var<const int>}); // expected-note {{instantiation of}}
  37   (void)sizeof(int{is_reference_var<int>}); // expected-note {{instantiation of}}
  38   (void)sizeof(int{is_float_var<int>}); // expected-error {{cannot be narrowed}} expected-note {{cast}}
  39 }