On Wed, 23 Mar 2022, Jason Merrill via Gcc-patches wrote:
> Here, DECL_DEPENDENT_P was false for the second using because Row<eT> is
> "the current instantiation", so lookup succeeds. But since Row itself has a
> dependent using-decl for operator(), the set of functions imported by the
> second using is dependent, so we should set the flag.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> PR c++/105006
>
> gcc/cp/ChangeLog:
>
> * name-lookup.cc (lookup_using_decl): Set DECL_DEPENDENT_P if lookup
> finds a dependent using.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/template/using30.C: New test.
> ---
> gcc/cp/name-lookup.cc | 15 +++++++++++++++
> gcc/testsuite/g++.dg/template/using30.C | 13 +++++++++++++
> 2 files changed, 28 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/template/using30.C
>
> diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
> index 323f96bcd24..ea947fabb7e 100644
> --- a/gcc/cp/name-lookup.cc
> +++ b/gcc/cp/name-lookup.cc
> @@ -5665,6 +5665,21 @@ lookup_using_decl (tree scope, name_lookup &lookup)
> lookup.value = lookup_member (binfo, lookup.name, /*protect=*/2,
> /*want_type=*/false, tf_none);
>
> + /* If the lookup in the base contains a dependent using, this
> + using is also dependent. */
> + if (!dependent_p && lookup.value)
I wonder if it'd be worthwhile to also test dependent_type_p (scope) here
here to avoid iterating over the lookup set when it can't possibly contain
a dependent using-decl.
> + {
> + tree val = lookup.value;
> + if (tree fns = maybe_get_fns (val))
> + val = fns;
> + for (tree f: lkp_range (val))
> + if (TREE_CODE (f) == USING_DECL && DECL_DEPENDENT_P (f))
> + {
> + dependent_p = true;
> + break;
> + }
> + }
> +
> if (!depscope && b_kind < bk_proper_base)
> {
> if (cxx_dialect >= cxx20 && lookup.value
> diff --git a/gcc/testsuite/g++.dg/template/using30.C
> b/gcc/testsuite/g++.dg/template/using30.C
> new file mode 100644
> index 00000000000..914252dd14c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/using30.C
> @@ -0,0 +1,13 @@
> +// PR c++/105006
> +
> +template<class eT>
> +class Row {
> + using eT::operator();
> + void operator()();
> + class fixed;
> +};
> +
> +template<class eT>
> +class Row<eT>::fixed : Row {
> + using Row::operator();
> +};
>
> base-commit: 4a9e92164a547afcf8cd3fc593c7660238ad2d59
> --
> 2.27.0
>
>
