1 // RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -verify %s
2 // RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -verify %s -DCLASS
3
4 #ifdef CLASS
5 struct Outer {
6 #endif
7
8 template<typename> struct A {};
9
10 // Valid forms.
11 A(int(&)[1]) -> A<int>;
12 explicit A(int(&)[2]) -> A<int>;
13
14 // Declarator pieces are not OK.
15 *A(int(&)[3]) -> A<int>; // expected-error {{cannot specify any part of a return type in the declaration of a deduction guide}}
16 &A(int(&)[4]) -> A<int>; // expected-error {{cannot specify any part of a return type in the declaration of a deduction guide}}
17 A(int(&)[5])[3] -> A<int>;
18 #ifdef CLASS // FIXME: These diagnostics are both pretty bad.
19 // expected-error@-2 {{function cannot return array type}} expected-error@-2 {{';'}}
20 #else
21 // expected-error@-4 {{expected function body after function declarator}}
22 #endif
23
24 (A[3])(int(&)[5][1]) -> A<int>; // expected-error {{'<deduction guide for A>' cannot be the name of a variable}}
25 #ifndef CLASS
26 // expected-error@-2 {{declared as array of functions}}
27 #endif
28 (*A)(int(&)[5][2]) -> A<int>; // expected-error {{'<deduction guide for A>' cannot be the name of a variable}}
29 (&A)(int(&)[5][3]) -> A<int>; // expected-error {{'<deduction guide for A>' cannot be the name of a variable}}
30 (*A(int))(int(&)[5][4]) -> A<int>; // expected-error {{cannot specify any part of a return type in the declaration of a deduction guide}}
31
32 // (Pending DR) attributes and parens around the declarator-id are OK.
33 [[deprecated]] A(int(&)[6]) [[]] -> A<int> [[]];
34 A [[]] (int(&)[7]) -> A<int>;
35 (A)(int(&)[8]) -> A<int>;
36
37 // ... but the trailing-return-type is part of the function-declarator as normal
38 (A(int(&)[9])) -> A<int>;
39 #ifdef CLASS // FIXME: These diagnostics are both pretty bad.
40 // expected-error@-2 {{deduction guide declaration without trailing return type}} expected-error@-2 {{';'}}
41 #else
42 // expected-error@-4 {{expected function body after function declarator}}
43 #endif
44 (A(int(&)[10]) -> A<int>); // expected-error {{trailing return type may not be nested within parentheses}}
45
46 // A trailing-return-type is mandatory.
47 A(int(&)[11]); // expected-error {{deduction guide declaration without trailing return type}}
48
49 // No type specifier is permitted; we don't even parse such cases as a deduction-guide.
50 int A(int) -> A<int>; // expected-error {{function with trailing return type must specify return type 'auto', not 'int'}}
51 template<typename T> struct B {}; // expected-note {{here}}
52 auto B(int) -> B<int>; // expected-error {{redefinition of 'B' as different kind of symbol}}
53
54 // No storage class specifier, function specifier, ...
55 friend A(int(&)[20]) -> A<int>;
56 #ifdef CLASS
57 // expected-error@-2 {{cannot declare a deduction guide as a friend}}
58 #else
59 // expected-error@-4 {{'friend' used outside of class}}
60 #endif
61 typedef A(int(&)[21]) -> A<int>; // expected-error {{deduction guide cannot be declared 'typedef'}}
62 constexpr A(int(&)[22]) -> A<int>; // expected-error {{deduction guide cannot be declared 'constexpr'}}
63 inline A(int(&)[23]) -> A<int>; // expected-error {{deduction guide cannot be declared 'inline'}}
64 static A(int(&)[24]) -> A<int>; // expected-error {{deduction guide cannot be declared 'static'}}
65 thread_local A(int(&)[25]) -> A<int>; // expected-error {{'thread_local' is only allowed on variable declarations}}
66 extern A(int(&)[26]) -> A<int>;
67 #ifdef CLASS
68 // expected-error@-2 {{storage class specified for a member}}
69 #else
70 // expected-error@-4 {{deduction guide cannot be declared 'extern'}}
71 #endif
72 mutable A(int(&)[27]) -> A<int>; // expected-error-re {{{{'mutable' cannot be applied to|illegal storage class on}} function}}
73 virtual A(int(&)[28]) -> A<int>; // expected-error {{'virtual' can only appear on non-static member functions}}
74 const A(int(&)[31]) -> A<int>; // expected-error {{deduction guide cannot be declared 'const'}}
75
76 const volatile static constexpr inline A(int(&)[29]) -> A<int>; // expected-error {{deduction guide cannot be declared 'static inline constexpr const volatile'}}
77
78 A(int(&)[30]) const -> A<int>; // expected-error {{deduction guide cannot have 'const' qualifier}}
79
80 // No definition is allowed.
AOuter81 A(int(&)[40]) -> A<int> {} // expected-error {{deduction guide cannot have a function definition}}
82 A(int(&)[41]) -> A<int> = default; // expected-error {{deduction guide cannot have a function definition}} expected-error {{only special member functions may be defaulted}}
83 A(int(&)[42]) -> A<int> = delete; // expected-error {{deduction guide cannot have a function definition}}
AOuter84 A(int(&)[43]) -> A<int> try {} catch (...) {} // expected-error {{deduction guide cannot have a function definition}}
85
86 #ifdef CLASS
87 };
88 #endif
89
90 namespace ExplicitInst {
91 // Explicit instantiation / specialization is not permitted.
92 template<typename T> struct B {};
93 template<typename T> B(T) -> B<T>;
94 template<> B(int) -> B<int>; // expected-error {{deduction guide cannot be explicitly specialized}}
95 extern template B(float) -> B<float>; // expected-error {{deduction guide cannot be explicitly instantiated}}
96 template B(char) -> B<char>; // expected-error {{deduction guide cannot be explicitly instantiated}}
97
98 // An attempt at partial specialization doesn't even parse as a deduction-guide.
99 template<typename T> B<T*>(T*) -> B<T*>; // expected-error 1+{{}} expected-note 0+{{}}
100
101 struct X {
102 template<typename T> struct C {};
103 template<typename T> C(T) -> C<T>;
104 template<> C(int) -> C<int>; // expected-error {{deduction guide cannot be explicitly specialized}}
105 extern template C(float) -> C<float>; // expected-error {{expected member name or ';'}}
106 template C(char) -> C<char>; // expected-error {{expected '<' after 'template'}}
107 };
108 }
109