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// RUN: %clang_cc1 -std=c++1z %s -verify
// The same restrictions apply to the parameter-declaration-clause of a
// deduction guide as in a function declaration.
template<typename T> struct A {};
A(void) -> A<int>; // ok
A(void, int) -> A<int>; // expected-error {{'void' must be the first and only parameter if specified}}
// We interpret this as also extending to the validity of redeclarations. It's
// a bit of a stretch (OK, a lot of a stretch) but it gives desirable answers.
A() -> A<int>; // ok, redeclaration
A() -> A<int>; // expected-note {{previous}}
A() -> A<float>; // FIXME: "functions" is a poor term. expected-error {{functions that differ only in their return type cannot be overloaded}}
template<typename T> A(T) -> A<typename T::foo>;
template<typename T> A(T) -> A<typename T::bar>; // ok, can overload on return type (SFINAE applies)
A(long) -> A<int>;
template<typename T = int> A(long) -> A<char>; // ok, non-template beats template as usual
// (Pending DR) The template-name shall name a class template.
template<typename T> using B = A<T>; // expected-note {{template}}
B() -> B<int>; // expected-error {{cannot specify deduction guide for alias template 'B'}}
// FIXME: expected-error@-1 {{declarator requires an identifier}}
template<typename T> int C;
C() -> int; // expected-error {{requires a type specifier}}
template<typename T> void D();
D() -> int; // expected-error {{requires a type specifier}}
template<template<typename> typename TT> struct E { // expected-note 2{{template}}
// FIXME: Should only diagnose this once!
TT(int) -> TT<int>; // expected-error 2{{cannot specify deduction guide for template template parameter 'TT'}} expected-error {{requires an identifier}}
};
A(int) -> int; // expected-error {{deduced type 'int' of deduction guide is not a specialization of template 'A'}}
template<typename T> A(T) -> B<T>; // expected-error {{deduced type 'B<T>' (aka 'A<type-parameter-0-0>') of deduction guide is not written as a specialization of template 'A'}}
template<typename T> A(T*) -> const A<T>; // expected-error {{deduced type 'const A<T>' of deduction guide is not a specialization of template 'A'}}
// A deduction-guide shall be declared in the same scope as the corresponding
// class template.
namespace WrongScope {
namespace {
template<typename T> struct AnonNS1 {}; // expected-note {{here}}
AnonNS1(float) -> AnonNS1<float>; // ok
}
AnonNS1(int) -> AnonNS1<int>; // expected-error {{deduction guide must be declared in the same scope as template 'WrongScope::}}
template<typename T> struct AnonNS2 {}; // expected-note {{here}}
namespace {
AnonNS1(char) -> AnonNS1<char>; // ok
AnonNS2(int) -> AnonNS2<int>; // expected-error {{deduction guide must be declared in the same scope as template 'WrongScope::AnonNS2'}}
}
namespace N {
template<typename T> struct NamedNS1 {}; // expected-note {{here}}
template<typename T> struct NamedNS2 {}; // expected-note {{here}}
}
using N::NamedNS1;
NamedNS1(int) -> NamedNS1<int>; // expected-error {{deduction guide must be declared in the same scope as template}}
using namespace N;
NamedNS2(int) -> NamedNS2<int>; // expected-error {{deduction guide must be declared in the same scope as template}}
struct ClassMemberA {
template<typename T> struct X {}; // expected-note {{here}}
};
struct ClassMemberB : ClassMemberA {
X(int) -> X<int>; // expected-error {{deduction guide must be declared in the same scope as template 'WrongScope::ClassMemberA::X'}}
};
template<typename T> struct Local {};
void f() {
Local(int) -> Local<int>; // expected-error {{expected}}
using WrongScope::Local;
Local(int) -> Local<int>; // expected-error {{expected}}
}
}
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