1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
2 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++1y %s -DCXX1Y
3 
4 struct NonLiteral { NonLiteral(); };
5 
6 // A type is a literal type if it is:
7 
8 // [C++1y] - void
9 constexpr void f() {}
10 #ifndef CXX1Y
11 // expected-error@-2 {{'void' is not a literal type}}
12 #endif
13 
14 // - a scalar type
15 constexpr int f1(double) { return 0; }
16 
17 // - a reference type
18 struct S { S(); };
19 constexpr int f2(S &) { return 0; }
20 
21 struct BeingDefined;
22 extern BeingDefined beingdefined;
23 struct BeingDefined {
24   static constexpr BeingDefined& t = beingdefined;
25 };
26 
27 // - a class type that has all of the following properties:
28 
29 // (implied) - it is complete
30 
31 struct Incomplete; // expected-note 2{{forward declaration of 'Incomplete'}}
32 template<class T> struct ClassTemp {};
33 
34 constexpr Incomplete incomplete = {}; // expected-error {{constexpr variable cannot have non-literal type 'const Incomplete'}} expected-note {{incomplete type 'const Incomplete' is not a literal type}}
35 constexpr Incomplete incomplete2[] = {}; // expected-error {{constexpr variable cannot have non-literal type 'Incomplete const[]'}} expected-note {{incomplete type 'Incomplete const[]' is not a literal type}}
36 constexpr ClassTemp<int> classtemplate = {};
37 constexpr ClassTemp<int> classtemplate2[] = {};
38 
39 //  - it has a trivial destructor
40 struct UserProvDtor {
41   constexpr int f() const; // expected-error {{non-literal type 'UserProvDtor' cannot have constexpr members}}
42   ~UserProvDtor(); // expected-note {{has a user-provided destructor}}
43 };
44 
45 struct NonTrivDtor {
46   constexpr NonTrivDtor();
47   constexpr int f() const; // expected-error {{non-literal type 'NonTrivDtor' cannot have constexpr members}}
48   virtual ~NonTrivDtor() = default; // expected-note {{has a non-trivial destructor}} expected-note {{because it is virtual}}
49 };
50 struct NonTrivDtorBase {
51   ~NonTrivDtorBase();
52 };
53 template<typename T>
54 struct DerivedFromNonTrivDtor : T { // expected-note {{'DerivedFromNonTrivDtor<NonTrivDtorBase>' is not literal because it has base class 'NonTrivDtorBase' of non-literal type}}
55   constexpr DerivedFromNonTrivDtor();
56 };
57 constexpr int f(DerivedFromNonTrivDtor<NonTrivDtorBase>) { return 0; } // expected-error {{constexpr function's 1st parameter type 'DerivedFromNonTrivDtor<NonTrivDtorBase>' is not a literal type}}
58 struct TrivDtor {
59   constexpr TrivDtor();
60 };
61 constexpr int f(TrivDtor) { return 0; }
62 struct TrivDefaultedDtor {
63   constexpr TrivDefaultedDtor();
64   ~TrivDefaultedDtor() = default;
65 };
66 constexpr int f(TrivDefaultedDtor) { return 0; }
67 
68 //  - it is an aggregate type or has at least one constexpr constructor or
69 //    constexpr constructor template that is not a copy or move constructor
70 struct Agg {
71   int a;
72   char *b;
73 };
74 constexpr int f3(Agg a) { return a.a; }
75 struct CtorTemplate {
76   template<typename T> constexpr CtorTemplate(T);
77 };
78 struct CopyCtorOnly { // expected-note {{'CopyCtorOnly' is not literal because it is not an aggregate and has no constexpr constructors other than copy or move constructors}}
79   constexpr CopyCtorOnly(CopyCtorOnly&);
80   constexpr int f() const; // expected-error {{non-literal type 'CopyCtorOnly' cannot have constexpr members}}
81 };
82 struct MoveCtorOnly { // expected-note {{no constexpr constructors other than copy or move constructors}}
83   constexpr MoveCtorOnly(MoveCtorOnly&&);
84   constexpr int f() const; // expected-error {{non-literal type 'MoveCtorOnly' cannot have constexpr members}}
85 };
86 template<typename T>
87 struct CtorArg {
88   constexpr CtorArg(T);
89 };
90 constexpr int f(CtorArg<int>) { return 0; } // ok
91 constexpr int f(CtorArg<NonLiteral>) { return 0; } // ok, ctor is still constexpr
92 // We have a special-case diagnostic for classes with virtual base classes.
93 struct VBase {};
94 struct HasVBase : virtual VBase {}; // expected-note 2{{virtual base class declared here}}
95 struct Derived : HasVBase {
96   constexpr Derived() {} // expected-error {{constexpr constructor not allowed in struct with virtual base class}}
97 };
98 template<typename T> struct DerivedFromVBase : T { // expected-note {{struct with virtual base class is not a literal type}}
99   constexpr DerivedFromVBase();
100 };
101 constexpr int f(DerivedFromVBase<HasVBase>) {} // expected-error {{constexpr function's 1st parameter type 'DerivedFromVBase<HasVBase>' is not a literal type}}
102 template<typename T> constexpr DerivedFromVBase<T>::DerivedFromVBase() : T() {}
103 constexpr int nVBase = (DerivedFromVBase<HasVBase>(), 0); // expected-error {{constant expression}} expected-note {{cannot construct object of type 'DerivedFromVBase<HasVBase>' with virtual base class in a constant expression}}
104 
105 //  - it has all non-static data members and base classes of literal types
106 struct NonLitMember {
107   S s; // expected-note {{has data member 's' of non-literal type 'S'}}
108 };
109 constexpr int f(NonLitMember) {} // expected-error {{1st parameter type 'NonLitMember' is not a literal type}}
110 struct NonLitBase :
111   S { // expected-note {{base class 'S' of non-literal type}}
112   constexpr NonLitBase();
113   constexpr int f() const { return 0; } // expected-error {{non-literal type 'NonLitBase' cannot have constexpr members}}
114 };
115 struct LitMemBase : Agg {
116   Agg agg;
117 };
118 template<typename T>
119 struct MemberType {
120   T t; // expected-note {{'MemberType<NonLiteral>' is not literal because it has data member 't' of non-literal type 'NonLiteral'}}
121   constexpr MemberType();
122 };
123 constexpr int f(MemberType<int>) { return 0; }
124 constexpr int f(MemberType<NonLiteral>) { return 0; } // expected-error {{not a literal type}}
125 
126 // - an array of literal type [C++1y] other than an array of runtime bound
127 struct ArrGood {
128   Agg agg[24];
129   double d[12];
130   TrivDtor td[3];
131   TrivDefaultedDtor tdd[3];
132 };
133 constexpr int f(ArrGood) { return 0; }
134 
135 struct ArrBad {
136   S s[3]; // expected-note {{data member 's' of non-literal type 'S [3]'}}
137 };
138 constexpr int f(ArrBad) { return 0; } // expected-error {{1st parameter type 'ArrBad' is not a literal type}}
139 
140 constexpr int arb(int n) {
141   int a[n]; // expected-error {{variable of non-literal type 'int [n]' cannot be defined in a constexpr function}}
142 }
143