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From: "m.cencora at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/108788] New: Lookup of injected class name should be
 type-dependent
Date: Tue, 14 Feb 2023 16:33:20 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108788

            Bug ID: 108788
           Summary: Lookup of injected class name should be type-dependent
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: m.cencora at gmail dot com
  Target Milestone: ---

Following code fails to compile on any gcc version. Works on all clang
versions.

It looks like inside template function get_templ_base the lookup of
v.templ_base::a is done eagerly, and finds templ_base at the global scope, =
and
hence errors out because the template parameters are missing.
But at this point qualified name "templ_base::a" should be type-dependent, =
so
lookup should be delayed until template instantiation, where 'templ_base' i=
s an
injected class name, so template paremeters shouldn't be required.

g++ -std=3Dc++11

struct base
{
    int a =3D 1;
};

template <typename T>
struct templ_base
{
    int a =3D 2;
};

namespace bar
{

struct base2
{
    int a =3D 3;
};

template <typename T>
struct templ_base2
{
    int a =3D 4;
};


}

struct foo : base, bar::templ_base2<char>, templ_base<int>, bar::base2
{
    int base =3D 5;
    int templ_base =3D 6;
    int base2 =3D 7;
    int templ_base2 =3D 8;
    int a =3D 9;
};

static_assert(foo{}.base::a =3D=3D 1, "");
static_assert(foo{}.templ_base::a =3D=3D 2, "");
static_assert(foo{}.base2::a =3D=3D 3, "");
static_assert(foo{}.templ_base2::a =3D=3D 4, "");


template <typename T>
int get_base(T&& v)
{
    return v.base::a;
}

template <typename T>
int get_templ_base(T&& v)
{
    return v.templ_base::a; // fails in all gcc versions
}

template <typename T>
int get_base2(T&& v)
{
    return v.base2::a; // fails for gcc <=3D 11
}

template <typename T>
int get_templ_base2(T&& v)
{
    return v.templ_base2::a;  // fails for gcc <=3D 11
}

int a =3D get_base(foo{});
int b =3D get_templ_base(foo{});
int c =3D get_base2(foo{});
int d =3D get_templ_base2(foo{});=