1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
2
3 // A converted constant expression of type T is a core constant expression,
4 int nonconst = 8; // expected-note 3 {{here}}
5 enum NonConstE : unsigned char { NCE = nonconst }; // expected-error {{enumerator value is not a constant expression}} expected-note {{read of non-const}}
6 template<int = nonconst> struct NonConstT {}; // expected-error {{non-type template argument is not a constant expression}} expected-note {{read of non-const}}
NonConstF()7 void NonConstF() {
8 switch (nonconst) {
9 case nonconst: // expected-error {{case value is not a constant expression}} expected-note {{read of non-const}}
10 break;
11 }
12 return;
13 }
14
15 // implicitly converted to a prvalue of type T, where the converted expression
16 // is a literal constant expression
17
a(int n)18 bool a(int n) {
19 constexpr char vowels[] = "aeiou";
20 switch (n) {
21 case vowels[0]:
22 case vowels[1]:
23 case vowels[2]:
24 case vowels[3]:
25 case vowels[4]:
26 static_assert(!vowels[5], "unexpected number of vowels");
27 return true;
28 }
29 return false;
30 }
31
32 // and the implicit conversion sequence contains only
33 //
34 // user-defined conversions,
operator intS35 struct S { constexpr operator int() const { return 5; } };
36 enum E : unsigned char { E5 = S(), E6, E10 = S() * 2, E1 = E5 / 5 };
37
38 // lvalue-to-rvalue conversions,
39 const E e10 = E10;
40 template<E> struct T {};
41 T<e10> s10;
42
43 // integral promotions, and
44 enum class EE { EE32 = ' ', EE65 = 'A', EE1 = (short)1, EE5 = E5 };
45
46 // integral conversions other than narrowing conversions
b(unsigned n)47 int b(unsigned n) {
48 switch (n) {
49 case E6:
50 case EE::EE32: // expected-error {{not implicitly convertible}}
51 case (int)EE::EE32:
52 case 1000:
53 case (long long)1e10: // expected-error {{case value evaluates to 10000000000, which cannot be narrowed to type 'unsigned int'}}
54 case -3: // expected-error {{case value evaluates to -3, which cannot be narrowed to type 'unsigned int'}}
55 return n;
56 }
57 return 0;
58 }
59 enum class EEE : unsigned short {
60 a = E6,
61 b = EE::EE32, // expected-error {{not implicitly convertible}}
62 c = (int)EE::EE32,
63 d = 1000,
64 e = 123456, // expected-error {{enumerator value evaluates to 123456, which cannot be narrowed to type 'unsigned short'}}
65 f = -3 // expected-error {{enumerator value evaluates to -3, which cannot be narrowed to type 'unsigned short'}}
66 };
67 template<unsigned char> using A = int;
68 using Int = A<E6>;
69 using Int = A<EE::EE32>; // expected-error {{not implicitly convertible}}
70 using Int = A<(int)EE::EE32>;
71 using Int = A<200>;
72 using Int = A<1000>; // expected-error {{template argument evaluates to 1000, which cannot be narrowed to type 'unsigned char'}}
73 using Int = A<-3>; // expected-error {{template argument evaluates to -3, which cannot be narrowed to type 'unsigned char'}}
74
75 // Note, conversions from integral or unscoped enumeration types to bool are
76 // integral conversions as well as boolean conversions.
77 template<typename T, T v> struct Val { static constexpr T value = v; };
78 static_assert(Val<bool, E1>::value == 1, ""); // ok
79 static_assert(Val<bool, '\0'>::value == 0, ""); // ok
80 static_assert(Val<bool, U'\1'>::value == 1, ""); // ok
81 static_assert(Val<bool, E5>::value == 1, ""); // expected-error {{5, which cannot be narrowed to type 'bool'}}
82
83 // (no other conversions are permitted)
84 using Int = A<1.0>; // expected-error {{conversion from 'double' to 'unsigned char' is not allowed in a converted constant expression}}
85 enum B : bool {
86 True = &a, // expected-error {{conversion from 'bool (*)(int)' to 'bool' is not allowed in a converted constant expression}}
87 False = nullptr // expected-error {{conversion from 'nullptr_t' to 'bool' is not allowed in a converted constant expression}}
88 };
c()89 void c() {
90 // Note, promoted type of switch is 'int'.
91 switch (bool b = a(5)) { // expected-warning {{boolean value}}
92 case 0.0f: // expected-error {{conversion from 'float' to 'int' is not allowed in a converted constant expression}}
93 break;
94 }
95 }
f()96 template <bool B> int f() { return B; } // expected-note {{candidate template ignored: invalid explicitly-specified argument for template parameter 'B'}}
97 template int f<&S::operator int>(); // expected-error {{does not refer to a function template}}
98 template int f<(bool)&S::operator int>();
99
100 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}}
101
102 namespace NonConstLValue {
103 struct S {
operator intNonConstLValue::S104 constexpr operator int() const { return 10; }
105 };
106 S s; // not constexpr
107 // Under the FDIS, this is not a converted constant expression.
108 // Under the new proposed wording, it is.
109 enum E : char { e = s };
110 }
111