On Tue, Apr 12, 2022 at 12:33 PM Jason Merrill <ja...@redhat.com> wrote:
>
> On 4/12/22 12:17, Patrick Palka wrote:
> > Here after dependent substitution of {Ts...} into the alias 'wrap',
> > since we never partially instantiate a requires-expr, we end up with a
> > requires-expr whose REQUIRES_EXPR_EXTRA_ARGS contains an
> > ARGUMENT_PACK_SELECT (which just resolves to the parameter pack Ts).
> > Then when looking up the resulting dependent specialization of A, we
> > crash from iterative_hash_template_arg since it deliberately doesn't
> > handle ARGUMENT_PACK_SELECT.
> >
> > Like with r12-7102-gdb5f1c17031ad8, it seems the right fix here is to
> > resolve ARGUMENT_PACK_SELECT arguments before storing them into an
> > extra args tree (such as REQUIRES_EXPR).
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk/11? For 11, we'd need to backport r12-7102 as a prereq.
>
> OK, that additional backport seems reasonable.
Thanks a lot, committed to trunk so far. I attempted backporting this
(along with the mentioned prereq r12-7102) but it seems we also need
to backport your r12-7857-gfc50d9a252c89c (from PR104008) before we
begin to accept the second testcase. (Now I remember why I sat on
this PR for so long :))
>
>
> > PR c++/103105
> > PR c++/103706
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (build_extra_args): Call preserve_args.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp2a/concepts-requires29.C: New test.
> > * g++.dg/cpp2a/concepts-requires29a.C: New test.
> > ---
> > gcc/cp/pt.cc | 2 +-
> > .../g++.dg/cpp2a/concepts-requires29.C | 18 +++++++++++++++
> > .../g++.dg/cpp2a/concepts-requires29a.C | 23 +++++++++++++++++++
> > 3 files changed, 42 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 78519562953..84712e6fc2f 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -13048,7 +13048,7 @@ build_extra_args (tree pattern, tree args,
> > tsubst_flags_t complain)
> > {
> > /* Make a copy of the extra arguments so that they won't get changed
> > out from under us. */
> > - tree extra = copy_template_args (args);
> > + tree extra = preserve_args (copy_template_args (args), /*cow_p=*/false);
> > if (local_specializations)
> > if (tree locals = extract_local_specs (pattern, complain))
> > extra = tree_cons (NULL_TREE, extra, locals);
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
> > b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
> > new file mode 100644
> > index 00000000000..5118df978c9
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
> > @@ -0,0 +1,18 @@
> > +// PR c++/103105
> > +// { dg-do compile { target c++20 } }
> > +
> > +template<bool> class A;
> > +
> > +template<class... Ts>
> > +using wrap = A<1 != (0 + ... + requires { Ts(); })>;
> > +
> > +template<class... Ts> using type = wrap<Ts...>;
> > +
> > +using ty0 = type<>;
> > +using ty0 = A<true>;
> > +
> > +using ty1 = type<int>;
> > +using ty1 = A<false>;
> > +
> > +using ty2 = type<int, int>;
> > +using ty2 = A<true>;
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
> > b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
> > new file mode 100644
> > index 00000000000..c41c1e6d039
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
> > @@ -0,0 +1,23 @@
> > +// PR c++/103105
> > +// { dg-do compile { target c++20 } }
> > +
> > +template<class...> struct list;
> > +template<bool> struct A;
> > +
> > +template<class T, class... Ts>
> > +using wrap = A<1 != (0 + ... + requires { T() = Ts(); })>;
> > +
> > +template<class... Ts>
> > +using type = list<wrap<Ts, Ts...>...>;
> > +
> > +using ty0 = type<>;
> > +using ty0 = list<>;
> > +
> > +using ty1 = type<int>;
> > +using ty1 = list<A<true>>;
> > +
> > +using ty2 = type<int, int>;
> > +using ty2 = list<A<true>, A<true>>;
> > +
> > +using ty3 = type<int, int, int>;
> > +using ty3 = list<A<true>, A<true>, A<true>>;
>
