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An improvement to ADL for the name declared by a friend declaration #5302

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xmh0511 opened this issue Feb 18, 2022 · 2 comments
Open

An improvement to ADL for the name declared by a friend declaration #5302

xmh0511 opened this issue Feb 18, 2022 · 2 comments

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@xmh0511
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xmh0511 commented Feb 18, 2022 •
edited

[basic.lookup.argdep] p4 is saying:

Argument-dependent lookup finds all declarations of functions and function templates that

  • are found by a search of any associated namespace, or
  • are declared as a friend ([class.friend]) of any class with a reachable definition in the set of associated entities, or

It sounds like we impose no requirement on the friend declarations when ADL. According to [dcl.meaning.general] p2, the declaration of a friend declaration does not bind a name. we define the concept for wording search that works on the name is bound. It is not suitable for friend declaration. The improvement is:

Argument-dependent lookup finds all declarations of functions and function templates that

  • [...], or
  • are declared as a friend of any class with a reachable definition in the set of associated entities, where the terminal names of the declarator-ids of the declarations are the same as the name that is being found.
@languagelawyer
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the terminal names of the declarator-ids of the declarations are the same as the name that is being found

What about

struct S;
namespace N
{
    void f(S&);
}

struct S
{
    friend void N::f(S&);
};

void f(S&&);

int main()
{
    S s;
    f(s);
}

@xmh0511
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xmh0511 commented Feb 18, 2022 •
edited

@languagelawyer Yes, you're correct. We should modify the above wording to that

are declared as a friend of any class T with a reachable definition in the set of associated entities, and whose target scopes are the namespace of which T is a member and the terminal names of the declarator-ids are the same as the name that is being found.

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@xmh0511 @languagelawyer