On Thu, 7 Mar 2024, Jason Merrill wrote:
> On 3/7/24 14:41, Patrick Palka wrote:
> > On Thu, 7 Mar 2024, Patrick Palka wrote:
> >
> > > On Wed, 6 Mar 2024, Jason Merrill wrote:
> > >
> > > > On 3/4/24 17:26, Patrick Palka wrote:
> > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > > > > OK for trunk?
> > > > >
> > > > > -- >8 --
> > > > >
> > > > > Alias templates are weird in that their specializations can appear in
> > > > > both decl_specializations and type_specializations. They appear in
> > > > > the
> > > > > latter only at parse time via finish_template_type. This should
> > > > > probably
> > > > > be revisited in GCC 15 since it seems sufficient to store them only in
> > > > > decl_specializations.
> > > >
> > > > It looks like most all of lookup_template_class is wrong for alias
> > > > templates.
> > > >
> > > > Can we move the alias template handling up higher and unconditionally
> > > > return
> > > > the result of tsubst?
> > >
> > > This works nicely (although we have to use instantiate_alias_template
> > > directly instead of tsubst since tsubst would first substitute the
> > > uncoerced arguments into the generic DECL_TI_ARGS which breaks for
> > > for parameter packs). And it allows for some nice simplifications in
> > > the modules code which had to handle alias template specializations
> > > specially.
> > >
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu.
> > >
> > > -- >8 --
> > >
> > > Subject: [PATCH] c++/modules: member alias tmpl partial inst [PR103994]
> > >
> > > Alias templates are weird in that their specializations can appear in
> > > both decl_specializations and type_specializations. They appear in the
> > > type table only at parse time via finish_template_type. There seems
> > > to be no good reason for this, and the code paths end up stepping over
> > > each other in particular for a partial alias template instantiation such
> > > as A<B>::key_arg<T> in the below modules testcase: the type code path
> > > (lookup_template_class) wants to set TI_TEMPLATE to the most general
> > > template whereas the decl code path (tsubst_template_decl called during
> > > instantiation of A<B>) already set TI_TEMPLATE to the partially
> > > instantiated TEMPLATE_DECL. This ends up confusing modules which
> > > decides to stream the logically equivalent TYPE_DECL and TEMPLATE_DECL
> > > for this partial alias template instantiation separately.
> > >
> > > This patch fixes this by making lookup_template_class dispatch to
> > > instantiatie_alias_template early for alias template specializations.
> > > In turn we now only add such specializations to the decl table and
> > > not also the type table. This admits some nice simplification in
> > > the modules code which otherwise has to cope with such specializations
> > > appearing in both tables.
> > >
> > > PR c++/103994
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * cp-tree.h (add_mergeable_specialization): Remove is_alias
> > > parameter.
> > > * module.cc (depset::disc_bits::DB_ALIAS_SPEC_BIT): Remove.
> > > (depset::is_alias): Remove.
> > > (merge_kind::MK_tmpl_alias_mask): Remove.
> > > (merge_kind::MK_alias_spec): Remove.
> > > (merge_kind_name): Remove entries for alias specializations.
> > > (trees_in::decl_value): Adjust add_mergeable_specialization
> > > calls.
> > > (trees_out::get_merge_kind) <case depset::EK_SPECIALIZATION>:
> > > Use MK_decl_spec for alias template specializations.
> > > (trees_out::key_mergeable): Simplify after MK_tmpl_alias_mask
> > > removal.
> > > (specialization_add): Don't allow alias templates when !decl_p.
> > > (depset::hash::add_specializations): Remove now-dead code
> > > accomodating alias template specializations in the type table.
> > > * pt.cc (lookup_template_class): Dispatch early to
> > > instantiate_alias_template for alias templates. Simplify
> > > accordingly.
> > > (add_mergeable_specialization): Remove alias_p parameter and
> > > simplify accordingly.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * g++.dg/modules/pr99425-1_b.H: s/alias/decl in dump scan.
> > > * g++.dg/modules/tpl-alias-1_a.H: Likewise.
> > > * g++.dg/modules/tpl-alias-2_a.H: New test.
> > > * g++.dg/modules/tpl-alias-2_b.C: New test.
> > > ---
> > > gcc/cp/cp-tree.h | 3 +-
> > > gcc/cp/module.cc | 50 ++----------
> > > gcc/cp/pt.cc | 84 ++++++++------------
> > > gcc/testsuite/g++.dg/modules/pr99425-1_b.H | 2 +-
> > > gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H | 2 +-
> > > gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H | 15 ++++
> > > gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C | 9 +++
> > > 7 files changed, 69 insertions(+), 96 deletions(-)
> > > create mode 100644 gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H
> > > create mode 100644 gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C
> > >
> > > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > > index 4469d965ef0..14895bc6585 100644
> > > --- a/gcc/cp/cp-tree.h
> > > +++ b/gcc/cp/cp-tree.h
> > > @@ -7642,8 +7642,7 @@ extern void walk_specializations (bool,
> > > void *);
> > > extern tree match_mergeable_specialization (bool is_decl,
> > > spec_entry *);
> > > extern unsigned get_mergeable_specialization_flags (tree tmpl, tree
> > > spec);
> > > -extern void add_mergeable_specialization (bool is_decl, bool
> > > is_alias,
> > > - spec_entry *,
> > > +extern void add_mergeable_specialization (bool is_decl, spec_entry
> > > *,
> > > tree outer, unsigned);
> > > extern tree add_to_template_args (tree, tree);
> > > extern tree add_outermost_template_args (tree, tree);
> > > diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> > > index 4ecd6d7c813..cc038ee9cba 100644
> > > --- a/gcc/cp/module.cc
> > > +++ b/gcc/cp/module.cc
> > > @@ -2306,10 +2306,7 @@ private:
> > > /* The following bits are not independent, but enumerating them is
> > > awkward. */
> > > DB_ALIAS_TMPL_INST_BIT, /* An alias template instantiation. */
> >
> > It seems we don't need DB_ALIAS_TMPL_INST_BIT anymore either, so the
> > updated patch below removes it too.
>
> OK.
Thanks a lot.
>
> > -- >8 --
> >
> > PR c++/103994
> >
> > gcc/cp/ChangeLog:
> >
> > * cp-tree.h (add_mergeable_specialization): Remove is_alias
> > parameter.
> > * module.cc (depset::disc_bits::DB_ALIAS_TMPL_INST_BIT): Remove.
> > (depset::disc_bits::DB_ALIAS_SPEC_BIT): Remove.
> > (depset::is_alias_tmpl_inst): Remove.
> > (depset::is_alias): Remove.
> > (merge_kind::MK_tmpl_alias_mask): Remove.
> > (merge_kind::MK_alias_spec): Remove.
> > (merge_kind_name): Remove entries for alias specializations.
> > (trees_out::core_vals) <case TEMPLATE_DECL>: Adjust after
> > removing is_alias_tmpl_inst.
> > (trees_in::decl_value): Adjust add_mergeable_specialization
> > calls.
> > (trees_out::get_merge_kind) <case depset::EK_SPECIALIZATION>:
> > Use MK_decl_spec for alias template specializations.
> > (trees_out::key_mergeable): Simplify after MK_tmpl_alias_mask
> > removal.
> > (depset::hash::make_dependency): Adjust after removing
> > DB_ALIAS_TMPL_INST_BIT.
> > (specialization_add): Don't allow alias templates when !decl_p.
> > (depset::hash::add_specializations): Remove now-dead code
> > accomodating alias template specializations in the type table.
> > * pt.cc (lookup_template_class): Dispatch early to
> > instantiate_alias_template for alias templates. Simplify
> > accordingly.
> > (add_mergeable_specialization): Remove alias_p parameter and
> > simplify accordingly.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/modules/pr99425-1_b.H: s/alias/decl in dump scan.
> > * g++.dg/modules/tpl-alias-1_a.H: Likewise.
> > * g++.dg/modules/tpl-alias-2_a.H: New test.
> > * g++.dg/modules/tpl-alias-2_b.C: New test.
> > ---
> > gcc/cp/cp-tree.h | 3 +-
> > gcc/cp/module.cc | 86 ++++----------------
> > gcc/cp/pt.cc | 84 ++++++++-----------
> > gcc/testsuite/g++.dg/modules/pr99425-1_b.H | 2 +-
> > gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H | 2 +-
> > gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H | 15 ++++
> > gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C | 9 ++
> > 7 files changed, 78 insertions(+), 123 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H
> > create mode 100644 gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C
> >
> > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > index 4469d965ef0..14895bc6585 100644
> > --- a/gcc/cp/cp-tree.h
> > +++ b/gcc/cp/cp-tree.h
> > @@ -7642,8 +7642,7 @@ extern void walk_specializations (bool,
> > void *);
> > extern tree match_mergeable_specialization (bool is_decl,
> > spec_entry *);
> > extern unsigned get_mergeable_specialization_flags (tree tmpl, tree spec);
> > -extern void add_mergeable_specialization (bool is_decl, bool
> > is_alias,
> > - spec_entry *,
> > +extern void add_mergeable_specialization (bool is_decl, spec_entry
> > *,
> > tree outer, unsigned);
> > extern tree add_to_template_args (tree, tree);
> > extern tree add_outermost_template_args (tree, tree);
> > diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> > index 4ecd6d7c813..dfe4536c0ae 100644
> > --- a/gcc/cp/module.cc
> > +++ b/gcc/cp/module.cc
> > @@ -2305,11 +2305,7 @@ private:
> > DB_HIDDEN_BIT, /* A hidden binding. */
> > /* The following bits are not independent, but enumerating them is
> > awkward. */
> > - DB_ALIAS_TMPL_INST_BIT, /* An alias template instantiation. */
> > - DB_ALIAS_SPEC_BIT, /* Specialization of an alias template
> > - (in both spec tables). */
> > - DB_TYPE_SPEC_BIT, /* Specialization in the type table.
> > - */
> > + DB_TYPE_SPEC_BIT, /* Specialization in the type table.
> > */
> > DB_FRIEND_SPEC_BIT, /* An instantiated template friend.
> > */
> > };
> > @@ -2400,14 +2396,6 @@ public:
> > {
> > return get_flag_bit<DB_UNREACHED_BIT> ();
> > }
> > - bool is_alias_tmpl_inst () const
> > - {
> > - return get_flag_bit<DB_ALIAS_TMPL_INST_BIT> ();
> > - }
> > - bool is_alias () const
> > - {
> > - return get_flag_bit<DB_ALIAS_SPEC_BIT> ();
> > - }
> > bool is_hidden () const
> > {
> > return get_flag_bit<DB_HIDDEN_BIT> ();
> > @@ -2782,13 +2770,11 @@ enum merge_kind
> > MK_template_mask = 0x10, /* A template specialization. */
> > MK_tmpl_decl_mask = 0x4, /* In decl table. */
> > - MK_tmpl_alias_mask = 0x2, /* Also in type table */
> > MK_tmpl_tmpl_mask = 0x1, /* We want TEMPLATE_DECL. */
> > MK_type_spec = MK_template_mask,
> > MK_decl_spec = MK_template_mask | MK_tmpl_decl_mask,
> > - MK_alias_spec = MK_decl_spec | MK_tmpl_alias_mask,
> > MK_hwm = 0x20
> > };
> > @@ -2806,7 +2792,7 @@ static char const *const merge_kind_name[MK_hwm] =
> > NULL, NULL,
> > "decl spec", "decl tmpl spec", /* 20,21 decl (template). */
> > - "alias spec", "alias tmpl spec", /* 22,23 alias (template). */
> > + NULL, NULL,
> > NULL, NULL, NULL, NULL,
> > NULL, NULL, NULL, NULL,
> > };
> > @@ -6356,8 +6342,7 @@ trees_out::core_vals (tree t)
> > gcc_checking_assert
> > (TREE_VISITED (((lang_tree_node
> > *)t)->template_decl.arguments));
> > gcc_checking_assert
> > - (TREE_VISITED (((lang_tree_node *)t)->template_decl.result)
> > - || dep_hash->find_dependency (t)->is_alias_tmpl_inst ());
> > + (TREE_VISITED (((lang_tree_node *)t)->template_decl.result));
> > if (DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P (t))
> > WT (DECL_CHAIN (t));
> > break;
> > @@ -8306,16 +8291,13 @@ trees_in::decl_value ()
> > {
> > bool is_type = TREE_CODE (inner) == TYPE_DECL;
> > spec.spec = is_type ? type : inner;
> > - add_mergeable_specialization (!is_type, false,
> > - &spec, decl, spec_flags);
> > + add_mergeable_specialization (!is_type, &spec, decl, spec_flags);
> > }
> > else if (mk & MK_template_mask)
> > {
> > bool is_type = !(mk & MK_tmpl_decl_mask);
> > spec.spec = is_type ? type : mk & MK_tmpl_tmpl_mask ? inner : decl;
> > - add_mergeable_specialization (!is_type,
> > - !is_type && mk & MK_tmpl_alias_mask,
> > - &spec, decl, spec_flags);
> > + add_mergeable_specialization (!is_type, &spec, decl, spec_flags);
> > }
> > if (NAMESPACE_SCOPE_P (decl)
> > @@ -8392,7 +8374,7 @@ trees_in::decl_value ()
> > if (!e)
> > {
> > spec.spec = inner;
> > - add_mergeable_specialization (true, false, &spec, decl, spec_flags);
> > + add_mergeable_specialization (true, &spec, decl, spec_flags);
> > }
> > else if (e != existing)
> > set_overrun ();
> > @@ -10620,8 +10602,6 @@ trees_out::get_merge_kind (tree decl, depset *dep)
> > mk = MK_friend_spec;
> > else if (dep->is_type_spec ())
> > mk = MK_type_spec;
> > - else if (dep->is_alias ())
> > - mk = MK_alias_spec;
> > else
> > mk = MK_decl_spec;
> > @@ -10732,11 +10712,6 @@ trees_out::key_mergeable (int tag, merge_kind mk,
> > tree decl, tree inner,
> > gcc_assert (existing);
> > if (mk & MK_tmpl_decl_mask)
> > {
> > - if (mk & MK_tmpl_alias_mask)
> > - /* It should be in both tables. */
> > - gcc_checking_assert
> > - (same_type_p (match_mergeable_specialization (false, entry),
> > - TREE_TYPE (existing)));
> > if (mk & MK_tmpl_tmpl_mask)
> > existing = DECL_TI_TEMPLATE (existing);
> > }
> > @@ -12830,17 +12805,12 @@ depset::hash::make_dependency (tree decl,
> > entity_kind ek)
> > bindings. */
> > *slot = dep = make_entity (decl, ek, has_def);
> > - if (TREE_CODE (decl) == TEMPLATE_DECL)
> > - {
> > - if (DECL_ALIAS_TEMPLATE_P (decl) && DECL_TEMPLATE_INFO (decl))
> > - dep->set_flag_bit<DB_ALIAS_TMPL_INST_BIT> ();
> > - else if (CHECKING_P)
> > - /* The template_result should otherwise not be in the
> > - table, or be an empty redirect (created above). */
> > - if (auto *eslot = entity_slot (DECL_TEMPLATE_RESULT (decl),
> > false))
> > - gcc_checking_assert ((*eslot)->get_entity_kind () == EK_REDIRECT
> > - && !(*eslot)->deps.length ());
> > - }
> > + if (CHECKING_P && TREE_CODE (decl) == TEMPLATE_DECL)
> > + /* The template_result should otherwise not be in the
> > + table, or be an empty redirect (created above). */
> > + if (auto *eslot = entity_slot (DECL_TEMPLATE_RESULT (decl), false))
> > + gcc_checking_assert ((*eslot)->get_entity_kind () == EK_REDIRECT
> > + && !(*eslot)->deps.length ());
> > if (ek != EK_USING)
> > {
> > @@ -13228,16 +13198,11 @@ specialization_add (bool decl_p, spec_entry
> > *entry, void *data_)
> > heuristic. We don't attempt to replicate that algorithm, but
> > observe its behaviour and reproduce it upon read back. */
> > - gcc_checking_assert (DECL_ALIAS_TEMPLATE_P (entry->tmpl)
> > - || TREE_CODE (entry->spec) == ENUMERAL_TYPE
> > + gcc_checking_assert (TREE_CODE (entry->spec) == ENUMERAL_TYPE
> > || DECL_CLASS_TEMPLATE_P (entry->tmpl));
> > - /* Only alias templates can appear in both tables (and
> > - if they're in the type table they must also be in the decl
> > - table). */
> > gcc_checking_assert
> > - (!match_mergeable_specialization (true, entry)
> > - == !DECL_ALIAS_TEMPLATE_P (entry->tmpl));
> > + (!match_mergeable_specialization (true, entry));
> > }
> > else if (VAR_OR_FUNCTION_DECL_P (entry->spec))
> > gcc_checking_assert (!DECL_LOCAL_DECL_P (entry->spec));
> > @@ -13293,7 +13258,6 @@ depset::hash::add_specializations (bool decl_p)
> > spec_entry *entry = data.pop ();
> > tree spec = entry->spec;
> > int use_tpl = 0;
> > - bool is_alias = false;
> > bool is_friend = false;
> > if (decl_p && DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P (entry->tmpl))
> > @@ -13301,13 +13265,7 @@ depset::hash::add_specializations (bool decl_p)
> > instantiation. */
> > is_friend = true;
> > - if (!decl_p && DECL_ALIAS_TEMPLATE_P (entry->tmpl))
> > - {
> > - spec = TYPE_NAME (spec);
> > - is_alias = true;
> > - }
> > -
> > - if (decl_p || is_alias)
> > + if (decl_p)
> > {
> > if (tree ti = DECL_TEMPLATE_INFO (spec))
> > {
> > @@ -13392,20 +13350,10 @@ depset::hash::add_specializations (bool decl_p)
> > gcc_checking_assert (!TREE_VISITED (spec));
> > depset *dep = make_dependency (spec, depset::EK_SPECIALIZATION);
> > if (dep->is_special ())
> > - {
> > - /* An already located specialization, this must be the TYPE
> > - corresponding to an alias_decl we found in the decl
> > - table. */
> > - spec_entry *other = reinterpret_cast <spec_entry *> (dep->deps[0]);
> > - gcc_checking_assert (!decl_p && is_alias && !dep->is_type_spec ());
> > - gcc_checking_assert (other->tmpl == entry->tmpl
> > - && template_args_equal (other->args,
> > entry->args)
> > - && TREE_TYPE (other->spec) == entry->spec);
> > - dep->set_flag_bit<DB_ALIAS_SPEC_BIT> ();
> > - }
> > + gcc_unreachable ();
> > else
> > {
> > - gcc_checking_assert (decl_p || !is_alias);
> > + gcc_checking_assert (decl_p);
> > if (dep->get_entity_kind () == depset::EK_REDIRECT)
> > dep = dep->deps[0];
> > else if (dep->get_entity_kind () == depset::EK_SPECIALIZATION)
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index d73f6d93485..99aa64b1cc3 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -10055,6 +10055,32 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > /* Now we should have enough arguments. */
> > gcc_assert (parm_depth == arg_depth);
> > + if (DECL_ALIAS_TEMPLATE_P (gen_tmpl))
> > + {
> > + /* The user referred to a specialization of an alias
> > + template represented by GEN_TMPL.
> > +
> > + [temp.alias]/2 says:
> > +
> > + When a template-id refers to the specialization of an
> > + alias template, it is equivalent to the associated
> > + type obtained by substitution of its
> > + template-arguments for the template-parameters in the
> > + type-id of the alias template. */
> > +
> > + t = instantiate_alias_template (gen_tmpl, arglist, complain);
> > + /* Note that the call above (by indirectly calling
> > + register_specialization in tsubst_decl) registers the
> > + TYPE_DECL representing the specialization of the alias
> > + template. So next time someone substitutes ARGLIST for
> > + the template parms into the alias template (GEN_TMPL),
> > + she'll get that TYPE_DECL back. */
> > +
> > + if (t == error_mark_node)
> > + return error_mark_node;
> > + return TREE_TYPE (t);
> > + }
>
> I'm surprised we don't still need the call to coerce_template_parms, a bit
> below this?
Luckily we can skip it since instantiate_alias_template already
immediately calls coerce_template_parms. I guess that's a nice
benefit of calling instantiate_alias_template directly instead
of going through tsubst.
>
> > /* From here on, we're only interested in the most general
> > template. */
> > @@ -10120,7 +10146,6 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > lookup. This prevents redundant checks on previously
> > instantiated specializations. */
> > if (flag_concepts
> > - && !DECL_ALIAS_TEMPLATE_P (gen_tmpl)
> > && !constraints_satisfied_p (gen_tmpl, arglist))
> > {
> > if (complain & tf_error)
> > @@ -10189,31 +10214,7 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > context = global_namespace;
> > /* Create the type. */
> > - if (DECL_ALIAS_TEMPLATE_P (gen_tmpl))
> > - {
> > - /* The user referred to a specialization of an alias
> > - template represented by GEN_TMPL.
> > -
> > - [temp.alias]/2 says:
> > -
> > - When a template-id refers to the specialization of an
> > - alias template, it is equivalent to the associated
> > - type obtained by substitution of its
> > - template-arguments for the template-parameters in the
> > - type-id of the alias template. */
> > -
> > - t = tsubst (TREE_TYPE (gen_tmpl), arglist, complain, in_decl);
> > - /* Note that the call above (by indirectly calling
> > - register_specialization in tsubst_decl) registers the
> > - TYPE_DECL representing the specialization of the alias
> > - template. So next time someone substitutes ARGLIST for
> > - the template parms into the alias template (GEN_TMPL),
> > - she'll get that TYPE_DECL back. */
> > -
> > - if (t == error_mark_node)
> > - return t;
> > - }
> > - else if (TREE_CODE (template_type) == ENUMERAL_TYPE)
> > + if (TREE_CODE (template_type) == ENUMERAL_TYPE)
> > {
> > if (!is_dependent_type)
> > {
> > @@ -10301,8 +10302,7 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > }
> > }
> > - if (OVERLOAD_TYPE_P (t)
> > - && !DECL_ALIAS_TEMPLATE_P (gen_tmpl))
> > + if (OVERLOAD_TYPE_P (t))
> > {
> > static const char *tags[] = {"abi_tag", "may_alias"};
> > @@ -10369,7 +10369,7 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > {
> > TREE_VEC_LENGTH (arglist)--;
> > ++processing_template_decl;
> > - tree tinfo = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (TREE_TYPE (gen_tmpl));
> > + tree tinfo = TYPE_TEMPLATE_INFO (TREE_TYPE (gen_tmpl));
> > tree partial_inst_args =
> > tsubst (INNERMOST_TEMPLATE_ARGS (TI_ARGS (tinfo)),
> > arglist, complain, NULL_TREE);
> > @@ -10407,17 +10407,9 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > TEMPLATE_PARM_LEVEL. */
> > found = tsubst (gen_tmpl, arglist, tf_none, NULL_TREE);
> > TREE_VEC_LENGTH (arglist)++;
> > - /* FOUND is either a proper class type, or an alias
> > - template specialization. In the later case, it's a
> > - TYPE_DECL, resulting from the substituting of arguments
> > - for parameters in the TYPE_DECL of the alias template
> > - done earlier. So be careful while getting the template
> > - of FOUND. */
> > found = (TREE_CODE (found) == TEMPLATE_DECL
> > ? found
> > - : (TREE_CODE (found) == TYPE_DECL
> > - ? DECL_TI_TEMPLATE (found)
> > - : CLASSTYPE_TI_TEMPLATE (found)));
> > + : CLASSTYPE_TI_TEMPLATE (found));
> > if (DECL_CLASS_TEMPLATE_P (found)
> > && CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_TYPE (found)))
> > @@ -10447,8 +10439,7 @@ lookup_template_class (tree d1, tree arglist, tree
> > in_decl, tree context,
> > DECL_TEMPLATE_INSTANTIATIONS (found));
> > if (TREE_CODE (template_type) == ENUMERAL_TYPE
> > - && !uses_template_parms (current_nonlambda_scope ())
> > - && !DECL_ALIAS_TEMPLATE_P (gen_tmpl))
> > + && !uses_template_parms (current_nonlambda_scope ()))
> > /* Now that the type has been registered on the instantiations
> > list, we set up the enumerators. Because the enumeration
> > constants may involve the enumeration type itself, we make
> > @@ -31578,8 +31569,8 @@ get_mergeable_specialization_flags (tree tmpl, tree
> > decl)
> > get_mergeable_specialization_flags. */
> > void
> > -add_mergeable_specialization (bool decl_p, bool alias_p, spec_entry *elt,
> > - tree decl, unsigned flags)
> > +add_mergeable_specialization (bool decl_p, spec_entry *elt, tree decl,
> > + unsigned flags)
> > {
> > hashval_t hash = spec_hasher::hash (elt);
> > if (decl_p)
> > @@ -31590,15 +31581,8 @@ add_mergeable_specialization (bool decl_p, bool
> > alias_p, spec_entry *elt,
> > auto entry = ggc_alloc<spec_entry> ();
> > *entry = *elt;
> > *slot = entry;
> > -
> > - if (alias_p)
> > - {
> > - elt->spec = TREE_TYPE (elt->spec);
> > - gcc_checking_assert (elt->spec);
> > - }
> > }
> > -
> > - if (!decl_p || alias_p)
> > + else
> > {
> > auto *slot = type_specializations->find_slot_with_hash (elt, hash,
> > INSERT);
> > diff --git a/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
> > b/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
> > index 53d28b4ef5e..e75b3129dd3 100644
> > --- a/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
> > +++ b/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
> > @@ -15,5 +15,5 @@ inline void widget (Cont parm)
> > ssize (parm);
> > }
> > -// { dg-final { scan-lang-dump {Read:-[0-9]*'s alias spec merge key
> > \(new\) type_decl:'::make_signed_t'\n ... Read:-[0-9]*'s type spec merge
> > key \(new\) type_decl:'::make_signed'\n Read:-[0-9]*'s named merge key
> > \(matched\) template_decl:'::template ssize'} module } }
> > +// { dg-final { scan-lang-dump {Read:-[0-9]*'s decl spec merge key \(new\)
> > type_decl:'::make_signed_t'\n ... Read:-[0-9]*'s type spec merge key
> > \(new\) type_decl:'::make_signed'\n Read:-[0-9]*'s named merge key
> > \(matched\) template_decl:'::template ssize'} module } }
> > diff --git a/gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H
> > b/gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H
> > index 37002ee9ae1..14a25be586f 100644
> > --- a/gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H
> > +++ b/gcc/testsuite/g++.dg/modules/tpl-alias-1_a.H
> > @@ -6,4 +6,4 @@
> > // { dg-final { scan-lang-dump {Writing decl tmpl spec:-[0-9]*
> > template_decl:'::allocator_traits<::allocator<long int>>::template
> > rebind_alloc<_Up>'} module } }
> > // { dg-final { scan-lang-dump {Writing decl tmpl spec:-[0-9]*
> > type_decl:'::allocator_traits<::allocator<long int>>::template
> > rebind_alloc<_Up>'} module } }
> > -// { dg-final { scan-lang-dump {Writing:-[0-9]*'s alias spec merge key
> > \(specialization\) type_decl:'::allocator_traits<::allocator<long
> > int>>::rebind_alloc<long int>'} module } }
> > +// { dg-final { scan-lang-dump {Writing:-[0-9]*'s decl spec merge key
> > \(specialization\) type_decl:'::allocator_traits<::allocator<long
> > int>>::rebind_alloc<long int>'} module } }
> > diff --git a/gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H
> > b/gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H
> > new file mode 100644
> > index 00000000000..76917f778e0
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/tpl-alias-2_a.H
> > @@ -0,0 +1,15 @@
> > +// PR c++/103994
> > +// { dg-additional-options -fmodule-header }
> > +// { dg-module-cmi {} }
> > +
> > +template<class>
> > +struct A {
> > + template<class> using key_arg = int;
> > +};
> > +
> > +struct B {
> > + template<class T>
> > + void f() {
> > + using type = A<B>::key_arg<T>;
> > + }
> > +};
> > diff --git a/gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C
> > b/gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C
> > new file mode 100644
> > index 00000000000..44fa5f42757
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/tpl-alias-2_b.C
> > @@ -0,0 +1,9 @@
> > +// PR c++/103994
> > +// { dg-additional-options -fmodules-ts }
> > +
> > +import "tpl-alias-2_a.H";
> > +
> > +int main() {
> > + B b;
> > + b.f<int>();
> > +}
>
>
