Name resolution for function declared in anonymous struct

Question

Should name resolution work for A, B, C in the following code in parameter list of f definition?

namespace ns
{
struct A {};
struct S
{
    struct B {};
    struct
    {
        struct C {};
        void f(A, B, C);
    } x;
};
}

#include <type_traits>

void std::type_identity_t<decltype(ns::S::x)>::f(A, B, C) {}

int main()
{
}

Actually it works in latest clang.

I'm not sure I understand your question. What part would you like detailed? The `type_identity`'s effect on name lookup? — StoryTeller - Unslander Monica, Nov 09 '20 at 10:15
Yes. Should it prohibit name resolution on the right side of last `::`. — Tomilov Anatoliy, Nov 09 '20 at 11:24
Does this answer your question? [The name lookup followed after qualified declarator-id](https://stackoverflow.com/questions/24038003/the-name-lookup-followed-after-qualified-declarator-id) [Name lookup after qualified declarator-id](https://stackoverflow.com/questions/24104101/name-lookup-after-qualified-declarator-id) — Language Lawyer, Nov 09 '20 at 11:58
This code works in current GCC too. Are you asking for a standard quote as to *why* it works? — Davis Herring, Nov 09 '20 at 14:43
Yes. Sadly I cannot put whole question in the title. The question is about the whole construction in the code snippet. — Tomilov Anatoliy, Nov 09 '20 at 19:16

score 2 · Accepted Answer · answered Nov 09 '20 at 15:19

[basic.lookup.unqual]/8 For the members of a class X, a name used ... in the definition of a class member outside of the definition of X, following the member's declarator-id(24), shall be declared in one of the following ways:
...
(8.2) — shall be a member of class X ..., or
(8.3) — if X is a nested class of class Y (11.4.10), shall be a member of Y,... or
...
(8.5) — if X is a member of namespace N, or is a nested class of a class that is a member of N, ... before the use of the name, in namespace N or in one of N's enclosing namespaces.

Footnote 24) That is, an unqualified name that occurs, for instance, in a type in the parameter-declaration-clause or in the noexcept-specifier.

Here X is decltype(ns::S::x), Y is S, N is ns. Therefore, A is found via (8.5), B via (8.3), C via (8.2).

But `std::type_identity_t` is not a class (`X`). It is a specialization of alias template. — Tomilov Anatoliy, Nov 09 '20 at 19:20
It's a `using` alias that names a class. It doesn't matter how `X` is referred to - whether by its original name, or typedef, or `using` alias, or `decltype`, or otherwise. — Igor Tandetnik, Nov 09 '20 at 23:39

Name resolution for function declared in anonymous struct

1 Answers1