1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
2 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 %s
3 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++1z %s
4
5 struct notlit { // expected-note {{not literal because}}
notlitnotlit6 notlit() {}
7 };
8 struct notlit2 {
notlit2notlit29 notlit2() {}
10 };
11
12 // valid declarations
13 constexpr int i1 = 0;
f1()14 constexpr int f1() { return 0; }
15 struct s1 {
16 constexpr static int mi1 = 0;
17 const static int mi2;
18 };
19 constexpr int s1::mi2 = 0;
20
21 // invalid declarations
22 // not a definition of an object
23 constexpr extern int i2; // expected-error {{constexpr variable declaration must be a definition}}
24 // not a literal type
25 constexpr notlit nl1; // expected-error {{constexpr variable cannot have non-literal type 'const notlit'}}
26 // function parameters
f2(constexpr int i)27 void f2(constexpr int i) {} // expected-error {{function parameter cannot be constexpr}}
28 // non-static member
29 struct s2 {
30 constexpr int mi1; // expected-error {{non-static data member cannot be constexpr; did you intend to make it const?}}
31 static constexpr int mi2;
32 #if __cplusplus <= 201402L
33 // expected-error@-2 {{requires an initializer}}
34 #else
35 // expected-error@-4 {{default initialization of an object of const}}
36 #endif
37 mutable constexpr int mi3 = 3; // expected-error-re {{non-static data member cannot be constexpr{{$}}}} expected-error {{'mutable' and 'const' cannot be mixed}}
38 };
39 // typedef
40 typedef constexpr int CI; // expected-error {{typedef cannot be constexpr}}
41 // tag
42 constexpr class C1 {}; // expected-error {{class cannot be marked constexpr}}
43 constexpr struct S1 {}; // expected-error {{struct cannot be marked constexpr}}
44 constexpr union U1 {}; // expected-error {{union cannot be marked constexpr}}
45 constexpr enum E1 {}; // expected-error {{enum cannot be marked constexpr}}
46 template <typename T> constexpr class TC1 {}; // expected-error {{class cannot be marked constexpr}}
47 template <typename T> constexpr struct TS1 {}; // expected-error {{struct cannot be marked constexpr}}
48 template <typename T> constexpr union TU1 {}; // expected-error {{union cannot be marked constexpr}}
49 class C2 {} constexpr; // expected-error {{class cannot be marked constexpr}}
50 struct S2 {} constexpr; // expected-error {{struct cannot be marked constexpr}}
51 union U2 {} constexpr; // expected-error {{union cannot be marked constexpr}}
52 enum E2 {} constexpr; // expected-error {{enum cannot be marked constexpr}}
53 constexpr class C3 {} c3 = C3();
54 constexpr struct S3 {} s3 = S3();
55 constexpr union U3 {} u3 = {};
56 constexpr enum E3 { V3 } e3 = V3;
57 class C4 {} constexpr c4 = C4();
58 struct S4 {} constexpr s4 = S4();
59 union U4 {} constexpr u4 = {};
60 enum E4 { V4 } constexpr e4 = V4;
61 constexpr int; // expected-error {{constexpr can only be used in variable and function declarations}}
62 // redeclaration mismatch
63 constexpr int f3(); // expected-note {{previous declaration is here}}
64 int f3(); // expected-error {{non-constexpr declaration of 'f3' follows constexpr declaration}}
65 int f4(); // expected-note {{previous declaration is here}}
66 constexpr int f4(); // expected-error {{constexpr declaration of 'f4' follows non-constexpr declaration}}
67 template<typename T> constexpr T f5(T);
68 template<typename T> constexpr T f5(T); // expected-note {{previous}}
69 template<typename T> T f5(T); // expected-error {{non-constexpr declaration of 'f5' follows constexpr declaration}}
70 template<typename T> T f6(T); // expected-note {{here}}
71 template<typename T> constexpr T f6(T); // expected-error {{constexpr declaration of 'f6' follows non-constexpr declaration}}
72 // destructor
73 struct ConstexprDtor {
74 constexpr ~ConstexprDtor() = default; // expected-error {{destructor cannot be marked constexpr}}
75 };
76
77 // template stuff
ft(T t)78 template <typename T> constexpr T ft(T t) { return t; }
gt(T t)79 template <typename T> T gt(T t) { return t; }
80 struct S {
81 template<typename T> constexpr T f(); // expected-warning 0-1{{C++14}} expected-note 0-1{{candidate}}
82 template <typename T>
83 T g() const; // expected-note-re {{candidate template ignored: could not match 'T (){{( __attribute__\(\(thiscall\)\))?}} const' against 'char (){{( __attribute__\(\(thiscall\)\))?}}'}}
84 };
85
86 // explicit specialization can differ in constepxr
ft(notlit nl)87 template <> notlit ft(notlit nl) { return nl; }
ft(char c)88 template <> char ft(char c) { return c; } // expected-note {{previous}}
89 template <> constexpr char ft(char nl); // expected-error {{constexpr declaration of 'ft<char>' follows non-constexpr declaration}}
gt(int nl)90 template <> constexpr int gt(int nl) { return nl; }
f() const91 template <> notlit S::f() const { return notlit(); }
92 #if __cplusplus >= 201402L
93 // expected-error@-2 {{no function template matches}}
94 #endif
g()95 template <> constexpr int S::g() { return 0; } // expected-note {{previous}}
96 #if __cplusplus < 201402L
97 // expected-warning@-2 {{C++14}}
98 #else
99 // expected-error@-4 {{does not match any declaration in 'S'}}
100 #endif
101 template <> int S::g() const; // expected-error {{non-constexpr declaration of 'g<int>' follows constexpr declaration}}
102 // specializations can drop the 'constexpr' but not the implied 'const'.
g()103 template <> char S::g() { return 0; } // expected-error {{no function template matches}}
g() const104 template <> double S::g() const { return 0; } // ok
105
106 constexpr int i3 = ft(1);
107
test()108 void test() {
109 // ignore constexpr when instantiating with non-literal
110 notlit2 nl2;
111 (void)ft(nl2);
112 }
113
114 // Examples from the standard:
115 constexpr int square(int x); // expected-note {{declared here}}
116 constexpr int bufsz = 1024;
117
118 constexpr struct pixel { // expected-error {{struct cannot be marked constexpr}}
119 int x;
120 int y;
121 constexpr pixel(int);
122 };
123
pixel(int a)124 constexpr pixel::pixel(int a)
125 : x(square(a)), y(square(a)) // expected-note {{undefined function 'square' cannot be used in a constant expression}}
126 { }
127
128 constexpr pixel small(2); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to 'pixel(2)'}}
129
square(int x)130 constexpr int square(int x) {
131 return x * x;
132 }
133
134 constexpr pixel large(4);
135
next(constexpr int x)136 int next(constexpr int x) { // expected-error {{function parameter cannot be constexpr}}
137 return x + 1;
138 }
139
140 extern constexpr int memsz; // expected-error {{constexpr variable declaration must be a definition}}
141
142 namespace {
143 struct A {
144 static constexpr int n = 0;
145 };
146 // FIXME: We should diagnose this prior to C++17.
147 const int &r = A::n;
148 }
149