On Sun, 29 May 2022, Jason Merrill wrote:
> On 5/29/22 22:10, Jason Merrill wrote:
> > On 5/27/22 14:05, Patrick Palka wrote:
> > > This makes us avoid substituting into the TEMPLATE_PARM_CONSTRAINT of
> > > each template parameter except as necessary for (friend) declaration
> > > matching, like we already do for the overall TEMPLATE_PARMS_CONSTRAINTS
> > > of a template parameter list.
> > >
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > > trunk and perhaps 12.2? Also tested on range-v3 and cmcstl2.
> >
> > Are there already tests that cover the friend cases?
Yes, by cpp2a/concepts-friend{2,3,7}.C I think.
>
> Also, don't you also need to handle specialization of partial instantiations?
Hmm, do you have an example? IIUC we call tsubst_friend_function and
tsubst_friend_class only from instantiate_class_template_1, which always
uses the most general template and full template argument set to
instantiate any friend declarations. So friend declarations are never
partially instantiated I think. (And IIUC non-friends are irrelevant
here since we don't ever want to substitute their constraints outside of
satisfaction.)
>
> > > PR c++/100374
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * pt.cc (tsubst_each_template_parm_constraint): Define.
> > > (tsubst_friend_function): Use it.
> > > (tsubst_friend_class): Use it.
> > > (tsubst_template_parm): Don't substitute TEMPLATE_PARM_CONSTRAINT.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * g++.dg/cpp2a/concepts-template-parm11.C: New test.
> > > ---
> > > gcc/cp/pt.cc | 35 ++++++++++++++++---
> > > .../g++.dg/cpp2a/concepts-template-parm11.C | 16 +++++++++
> > > 2 files changed, 47 insertions(+), 4 deletions(-)
> > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
> > >
> > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > > index 24bbe2f4060..ec168234325 100644
> > > --- a/gcc/cp/pt.cc
> > > +++ b/gcc/cp/pt.cc
> > > @@ -184,6 +184,7 @@ static int unify_pack_expansion (tree, tree, tree,
> > > tree, unification_kind_t, bool, bool);
> > > static tree copy_template_args (tree);
> > > static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
> > > +static void tsubst_each_template_parm_constraint (tree, tree,
> > > tsubst_flags_t);
> > > tree most_specialized_partial_spec (tree, tsubst_flags_t);
> > > static tree tsubst_aggr_type (tree, tree, tsubst_flags_t, tree, int);
> > > static tree tsubst_arg_types (tree, tree, tree, tsubst_flags_t, tree);
> > > @@ -11254,7 +11255,12 @@ tsubst_friend_function (tree decl, tree args)
> > > tree parms = DECL_TEMPLATE_PARMS (new_friend);
> > > tree treqs = TEMPLATE_PARMS_CONSTRAINTS (parms);
> > > treqs = maybe_substitute_reqs_for (treqs, new_friend);
> > > - TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
> > > + if (treqs != TEMPLATE_PARMS_CONSTRAINTS (parms))
> > > + {
> > > + TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
> > > + /* As well as each TEMPLATE_PARM_CONSTRAINT. */
> > > + tsubst_each_template_parm_constraint (parms, args,
> > > tf_warning_or_error);
> > > + }
> > > }
> > > /* The mangled name for the NEW_FRIEND is incorrect. The function
> > > @@ -11500,6 +11506,8 @@ tsubst_friend_class (tree friend_tmpl, tree args)
> > > {
> > > tree parms = tsubst_template_parms (DECL_TEMPLATE_PARMS
> > > (friend_tmpl),
> > > args, tf_warning_or_error);
> > > + tsubst_each_template_parm_constraint (parms, args,
> > > + tf_warning_or_error);
> > > location_t saved_input_location = input_location;
> > > input_location = DECL_SOURCE_LOCATION (friend_tmpl);
> > > tree cons = get_constraints (tmpl);
> > > @@ -11534,6 +11542,8 @@ tsubst_friend_class (tree friend_tmpl, tree args)
> > > DECL_FRIEND_CONTEXT (friend_tmpl));
> > > --processing_template_decl;
> > > set_constraints (tmpl, ci);
> > > + tsubst_each_template_parm_constraint (DECL_TEMPLATE_PARMS
> > > (tmpl),
> > > + args, tf_warning_or_error);
> > > }
> > > /* Inject this template into the enclosing namspace scope. */
> > > @@ -13656,7 +13666,6 @@ tsubst_template_parm (tree t, tree args,
> > > tsubst_flags_t complain)
> > > default_value = TREE_PURPOSE (t);
> > > parm_decl = TREE_VALUE (t);
> > > - tree constraint = TEMPLATE_PARM_CONSTRAINTS (t);
> > > parm_decl = tsubst (parm_decl, args, complain, NULL_TREE);
> > > if (TREE_CODE (parm_decl) == PARM_DECL
> > > @@ -13664,13 +13673,31 @@ tsubst_template_parm (tree t, tree args,
> > > tsubst_flags_t complain)
> > > parm_decl = error_mark_node;
> > > default_value = tsubst_template_arg (default_value, args,
> > > complain, NULL_TREE);
> > > - constraint = tsubst_constraint (constraint, args, complain, NULL_TREE);
> > > tree r = build_tree_list (default_value, parm_decl);
> > > - TEMPLATE_PARM_CONSTRAINTS (r) = constraint;
> > > + TEMPLATE_PARM_CONSTRAINTS (r) = TEMPLATE_PARM_CONSTRAINTS (t);
> > > return r;
> > > }
> > > +/* Substitute in-place the TEMPLATE_PARM_CONSTRAINT of each template
> > > + parameter in PARMS for sake of declaration matching. */
> > > +
> > > +static void
> > > +tsubst_each_template_parm_constraint (tree parms, tree args,
> > > + tsubst_flags_t complain)
> > > +{
> > > + ++processing_template_decl;
> > > + for (; parms; parms = TREE_CHAIN (parms))
> > > + {
> > > + tree level = TREE_VALUE (parms);
> > > + for (tree parm : tree_vec_range (level))
> > > + TEMPLATE_PARM_CONSTRAINTS (parm)
> > > + = tsubst_constraint (TEMPLATE_PARM_CONSTRAINTS (parm), args,
> > > + complain, NULL_TREE);
> > > + }
> > > + --processing_template_decl;
> > > +}
> > > +
> > > /* Substitute the ARGS into the indicated aggregate (or enumeration)
> > > type T. If T is not an aggregate or enumeration type, it is
> > > handled as if by tsubst. IN_DECL is as for tsubst. If
> > > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
> > > b/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
> > > new file mode 100644
> > > index 00000000000..f70de341a07
> > > --- /dev/null
> > > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-template-parm11.C
> > > @@ -0,0 +1,16 @@
> > > +// PR c++/100374
> > > +// { dg-do compile { target c++20 } }
> > > +
> > > +template<class T, class U>
> > > +concept C = true;
> > > +
> > > +template<class T>
> > > +struct A {
> > > + template<C<typename T::value_type> U>
> > > + void f();
> > > +
> > > + template<C<typename T::value_type> U>
> > > + struct B;
> > > +};
> > > +
> > > +template struct A<float>;
> >
>
>
