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}}
NonConstF()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
a(int n)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,
operator intS36 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,
b(unsigned n)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 = nullptr // expected-error {{conversion from 'nullptr_t' to 'bool' is not allowed in a converted constant expression}}
99 };
c()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 }
f()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 {
operator intNonConstLValue::S115 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