[PATCH] c++: don't substitute TEMPLATE_PARM_CONSTRAINT [PR100374]
Jason Merrill
jason@redhat.com
Tue May 31 19:02:42 GMT 2022
On 5/31/22 08:56, Patrick Palka wrote:
> 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.)
From C++20 CA104:
template <class T> struct A {
template <class U> U f(U) requires C<typename T::type>;
template <class U> U f(U) requires C<T>;
};
// Substitute int for T in above requirements to find match.
template <> template <class U> U A<int>::f(U) requires C<int> { }
>>>> 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>;
>>>
>>
More information about the Gcc-patches
mailing list