1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s 2 // RUN: %clang_cc1 -fsyntax-only -std=c++1z -verify %s 3 4 // A converted constant expression of type T is a core constant expression, 5 int nonconst = 8; // expected-note 3 {{here}} 6 enum NonConstE : unsigned char { NCE = nonconst }; // expected-error {{enumerator value is not a constant expression}} expected-note {{read of non-const}} 7 template<int = nonconst> struct NonConstT {}; // expected-error {{non-type template argument is not a constant expression}} expected-note {{read of non-const}} 8 void NonConstF() { 9 switch (nonconst) { 10 case nonconst: // expected-error {{case value is not a constant expression}} expected-note {{read of non-const}} 11 break; 12 } 13 return; 14 } 15 16 // implicitly converted to a prvalue of type T, where the converted expression 17 // is a literal constant expression 18 19 bool a(int n) { 20 constexpr char vowels[] = "aeiou"; 21 switch (n) { 22 case vowels[0]: 23 case vowels[1]: 24 case vowels[2]: 25 case vowels[3]: 26 case vowels[4]: 27 static_assert(!vowels[5], "unexpected number of vowels"); 28 return true; 29 } 30 return false; 31 } 32 33 // and the implicit conversion sequence contains only 34 // 35 // user-defined conversions, 36 struct S { constexpr operator int() const { return 5; } }; 37 enum E : unsigned char { E5 = S(), E6, E10 = S() * 2, E1 = E5 / 5 }; 38 39 // lvalue-to-rvalue conversions, 40 const E e10 = E10; 41 template<E> struct T {}; 42 T<e10> s10; 43 44 // integral promotions, 45 enum class EE { EE32 = ' ', EE65 = 'A', EE1 = (short)1, EE5 = E5 }; 46 47 // integral conversions other than narrowing conversions, 48 int b(unsigned n) { 49 switch (n) { 50 case E6: 51 case EE::EE32: // expected-error {{not implicitly convertible}} 52 case (int)EE::EE32: 53 case 1000: 54 case (long long)1e10: // expected-error {{case value evaluates to 10000000000, which cannot be narrowed to type 'unsigned int'}} 55 case -3: // expected-error {{case value evaluates to -3, which cannot be narrowed to type 'unsigned int'}} 56 return n; 57 } 58 return 0; 59 } 60 enum class EEE : unsigned short { 61 a = E6, 62 b = EE::EE32, // expected-error {{not implicitly convertible}} 63 c = (int)EE::EE32, 64 d = 1000, 65 e = 123456, // expected-error {{enumerator value evaluates to 123456, which cannot be narrowed to type 'unsigned short'}} 66 f = -3 // expected-error {{enumerator value evaluates to -3, which cannot be narrowed to type 'unsigned short'}} 67 }; 68 template<unsigned char> using A = int; 69 using Int = A<E6>; 70 using Int = A<EE::EE32>; // expected-error {{not implicitly convertible}} 71 using Int = A<(int)EE::EE32>; 72 using Int = A<200>; 73 using Int = A<1000>; // expected-error {{template argument evaluates to 1000, which cannot be narrowed to type 'unsigned char'}} 74 using Int = A<-3>; // expected-error {{template argument evaluates to -3, which cannot be narrowed to type 'unsigned char'}} 75 76 // Note, conversions from integral or unscoped enumeration types to bool are 77 // integral conversions as well as boolean conversions. 78 // FIXME: Per core issue 1407, this is not correct. 79 template<typename T, T v> struct Val { static constexpr T value = v; }; 80 static_assert(Val<bool, E1>::value == 1, ""); // ok 81 static_assert(Val<bool, '\0'>::value == 0, ""); // ok 82 static_assert(Val<bool, U'\1'>::value == 1, ""); // ok 83 static_assert(Val<bool, E5>::value == 1, ""); // expected-error {{5, which cannot be narrowed to type 'bool'}} 84 85 // function pointer conversions [C++17] 86 void noexcept_false() noexcept(false); 87 void noexcept_true() noexcept(true); 88 Val<decltype(&noexcept_false), &noexcept_true> remove_noexcept; 89 Val<decltype(&noexcept_true), &noexcept_false> add_noexcept; 90 #if __cplusplus > 201402L 91 // expected-error@-2 {{value of type 'void (*)() noexcept(false)' is not implicitly convertible to 'void (*)() noexcept'}} 92 #endif 93 94 // (no other conversions are permitted) 95 using Int = A<1.0>; // expected-error {{conversion from 'double' to 'unsigned char' is not allowed in a converted constant expression}} 96 enum B : bool { 97 True = &a, // expected-error {{conversion from 'bool (*)(int)' to 'bool' is not allowed in a converted constant expression}} 98 False = 0.0, // expected-error {{conversion from 'double' to 'bool' is not allowed in a converted constant expression}} 99 }; 100 void c() { 101 // Note, promoted type of switch is 'int'. 102 switch (bool b = a(5)) { // expected-warning {{boolean value}} 103 case 0.0f: // expected-error {{conversion from 'float' to 'int' is not allowed in a converted constant expression}} 104 break; 105 } 106 } 107 template <bool B> int f() { return B; } // expected-note {{candidate template ignored: invalid explicitly-specified argument for template parameter 'B'}} 108 template int f<&S::operator int>(); // expected-error {{does not refer to a function template}} 109 template int f<(bool)&S::operator int>(); 110 111 int n = Val<bool, &S::operator int>::value; // expected-error-re {{conversion from 'int (S::*)(){{( __attribute__\(\(thiscall\)\))?}} const' to 'bool' is not allowed in a converted constant expression}} 112 113 namespace NonConstLValue { 114 struct S { 115 constexpr operator int() const { return 10; } 116 }; 117 S s; // not constexpr 118 // Under the FDIS, this is not a converted constant expression. 119 // Under the new proposed wording, it is. 120 enum E : char { e = s }; 121 } 122