From: Jason Merrill <jason@redhat.com>
To: Patrick Palka <ppalka@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH 1/2] c++: requires-exprs and partial constraint subst [PR112769]
Date: Fri, 2 Feb 2024 16:05:48 -0500 [thread overview]
Message-ID: <124440ff-6522-44b7-96a6-803a1840d4b7@redhat.com> (raw)
In-Reply-To: <720eaacc-cd6a-8a66-e057-752c6a21183d@idea>
On 2/2/24 15:57, Patrick Palka wrote:
> On Fri, 2 Feb 2024, Patrick Palka wrote:
>
>> On Fri, 2 Feb 2024, Jason Merrill wrote:
>>
>>> On 2/2/24 14:41, Patrick Palka wrote:
>>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this
>>>> look OK for trunk?
>>>>
>>>> -- >8 --
>>>>
>>>> In r11-3261-gb28b621ac67bee we made tsubst_requires_expr never partially
>>>> substitute into a requires-expression so as to avoid checking its
>>>> requirements out of order during e.g. generic lambda regeneration.
>>>>
>>>> Unfortunately we still do need to partially substitute into a
>>>> requires-expression in rare cases, in particular when it's used in
>>>> associated constraints that we are directly substituting for sake of
>>>> declaration matching or dguide constraint rewriting. We can identify
>>>> this situation by checking processing_constraint_expression_p, so this
>>>> patch uses this predicate to control whether we defer substitution or
>>>> partially substitute. The entering_scope=true change in tsubst_baselink
>>>> is needed to avoid ICEing from tsubst_baselink during name lookup when
>>>> rewriting std::ranges::ref_view's dguide constraints.
>>>
>>> Actually, I don't think we want to enter the scope when rewriting constraints.
>>> Would tsubst_scope work instead?
>>
>> Oops yes, because of the maybe_dependent_member_ref stuff, the handling
>> for which doesn't trigger here for some reason. Ah, I think it's
>> because the tf_dguide flag gets dropped during tsubst_requires_expr
>> since it uses tf_none rather than complain & ~tf_warning_or_error
>> which would preserve special tsubst flags such as tf_dguide. I'll fix...
>
> Like so? Lightly tested so far, bootstrap+regtest in progress.
OK, thanks.
> -- >8 --
>
> Subject: [PATCH v2] c++: requires-exprs and partial constraint subst [PR112769]
>
> In r11-3261-gb28b621ac67bee we made tsubst_requires_expr never partially
> substitute into a requires-expression so as to avoid checking its
> requirements out of order during e.g. generic lambda regeneration.
>
> Unfortunately we still do need to partially substitute into a
> requires-expression in rare cases, in particular when it's used in
> associated constraints that we are directly substituting for sake of
> declaration matching or dguide constraint rewriting. We can identify
> this situation by checking processing_constraint_expression_p, so this
> patch uses this predicate to control whether we defer substitution or
> partially substitute.
>
> In turn, tsubst_requires_expr now needs to propagate semantic tsubst flags
> rather than just using tf_none, in particular for dguide constraint rewriting
> which sets tf_dguide.
>
> PR c++/112769
> PR c++/110006
>
> gcc/cp/ChangeLog:
>
> * constraint.cc (subst_info::quiet): Accomodate non-diagnostic
> tsubst flags.
> (tsubst_valid_expression_requirement): Likewise.
> (tsubst_simple_requirement): Likewise. Return a substituted _REQ
> node when processing_template_decl.
> (tsubst_type_requirement_1): Accomodate non-diagnostic tsubst
> flags.
> (tsubst_type_requirement): Return a substituted _REQ node when
> processing_template_decl.
> (tsubst_compound_requirement): Likewise. Accomodate non-diagnostic
> tsubst flags.
> (tsubst_nested_requirement): Likewise.
> (tsubst_requires_expr): Don't defer partial substitution when
> processing_constraint_expression_p is true, in which case return
> a substituted REQUIRES_EXPR.
> * pt.cc (tsubst_expr) <case REQUIRES_EXPR>: Accomodate
> non-diagnostic tsubst flags.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/class-deduction-alias18.C: New test.
> * g++.dg/cpp2a/concepts-friend16.C: New test.
> ---
> gcc/cp/constraint.cc | 56 +++++++++++++++----
> gcc/cp/pt.cc | 3 +-
> .../g++.dg/cpp2a/class-deduction-alias18.C | 13 +++++
> .../g++.dg/cpp2a/concepts-friend16.C | 25 +++++++++
> 4 files changed, 84 insertions(+), 13 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
>
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index fef68cf7ab2..d9569013bd3 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -85,7 +85,7 @@ struct subst_info
> /* True if we should not diagnose errors. */
> bool quiet() const
> {
> - return complain == tf_none;
> + return !(complain & tf_warning_or_error);
> }
>
> /* True if we should diagnose errors. */
> @@ -1991,8 +1991,9 @@ hash_placeholder_constraint (tree c)
> static tree
> tsubst_valid_expression_requirement (tree t, tree args, sat_info info)
> {
> - tree r = tsubst_expr (t, args, tf_none, info.in_decl);
> - if (convert_to_void (r, ICV_STATEMENT, tf_none) != error_mark_node)
> + tsubst_flags_t quiet = info.complain & ~tf_warning_or_error;
> + tree r = tsubst_expr (t, args, quiet, info.in_decl);
> + if (convert_to_void (r, ICV_STATEMENT, quiet) != error_mark_node)
> return r;
>
> if (info.diagnose_unsatisfaction_p ())
> @@ -2028,6 +2029,8 @@ tsubst_simple_requirement (tree t, tree args, sat_info info)
> tree expr = tsubst_valid_expression_requirement (t0, args, info);
> if (expr == error_mark_node)
> return error_mark_node;
> + if (processing_template_decl)
> + return finish_simple_requirement (EXPR_LOCATION (t), expr);
> return boolean_true_node;
> }
>
> @@ -2037,7 +2040,8 @@ tsubst_simple_requirement (tree t, tree args, sat_info info)
> static tree
> tsubst_type_requirement_1 (tree t, tree args, sat_info info, location_t loc)
> {
> - tree r = tsubst (t, args, tf_none, info.in_decl);
> + tsubst_flags_t quiet = info.complain & ~tf_warning_or_error;
> + tree r = tsubst (t, args, quiet, info.in_decl);
> if (r != error_mark_node)
> return r;
>
> @@ -2068,6 +2072,8 @@ tsubst_type_requirement (tree t, tree args, sat_info info)
> tree type = tsubst_type_requirement_1 (t0, args, info, EXPR_LOCATION (t));
> if (type == error_mark_node)
> return error_mark_node;
> + if (processing_template_decl)
> + return finish_type_requirement (EXPR_LOCATION (t), type);
> return boolean_true_node;
> }
>
> @@ -2124,9 +2130,11 @@ tsubst_compound_requirement (tree t, tree args, sat_info info)
>
> location_t loc = cp_expr_loc_or_input_loc (expr);
>
> + subst_info quiet (info.complain & ~tf_warning_or_error, info.in_decl);
> +
> /* Check the noexcept condition. */
> bool noexcept_p = COMPOUND_REQ_NOEXCEPT_P (t);
> - if (noexcept_p && !expr_noexcept_p (expr, tf_none))
> + if (noexcept_p && !expr_noexcept_p (expr, quiet.complain))
> {
> if (info.diagnose_unsatisfaction_p ())
> inform (loc, "%qE is not %<noexcept%>", expr);
> @@ -2139,8 +2147,6 @@ tsubst_compound_requirement (tree t, tree args, sat_info info)
> if (type == error_mark_node)
> return error_mark_node;
>
> - subst_info quiet (tf_none, info.in_decl);
> -
> /* Check expression against the result type. */
> if (type)
> {
> @@ -2182,6 +2188,9 @@ tsubst_compound_requirement (tree t, tree args, sat_info info)
> }
> }
>
> + if (processing_template_decl)
> + return finish_compound_requirement (EXPR_LOCATION (t),
> + expr, type, noexcept_p);
> return boolean_true_node;
> }
>
> @@ -2190,7 +2199,16 @@ tsubst_compound_requirement (tree t, tree args, sat_info info)
> static tree
> tsubst_nested_requirement (tree t, tree args, sat_info info)
> {
> - sat_info quiet (tf_none, info.in_decl);
> + if (processing_template_decl)
> + {
> + tree req = TREE_OPERAND (t, 0);
> + req = tsubst_constraint (req, args, info.complain, info.in_decl);
> + if (req == error_mark_node)
> + return error_mark_node;
> + return finish_nested_requirement (EXPR_LOCATION (t), req);
> + }
> +
> + sat_info quiet (info.complain & ~tf_warning_or_error, info.in_decl);
> tree result = constraint_satisfaction_value (t, args, quiet);
> if (result == boolean_true_node)
> return boolean_true_node;
> @@ -2330,18 +2348,25 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
>
> args = add_extra_args (REQUIRES_EXPR_EXTRA_ARGS (t), args,
> info.complain, info.in_decl);
> - if (processing_template_decl)
> + if (processing_template_decl
> + && !processing_constraint_expression_p ())
> {
> /* We're partially instantiating a generic lambda. Substituting into
> this requires-expression now may cause its requirements to get
> checked out of order, so instead just remember the template
> - arguments and wait until we can substitute them all at once. */
> + arguments and wait until we can substitute them all at once.
> +
> + Except if this requires-expr is part of associated constraints
> + that we're substituting into directly (for e.g. declaration
> + matching or dguide constraint rewriting), in which case we need
> + to partially substitute. */
> t = copy_node (t);
> REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
> return t;
> }
>
> - if (tree parms = REQUIRES_EXPR_PARMS (t))
> + tree parms = REQUIRES_EXPR_PARMS (t);
> + if (parms)
> {
> parms = tsubst_constraint_variables (parms, args, info);
> if (parms == error_mark_node)
> @@ -2349,10 +2374,13 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
> }
>
> tree result = boolean_true_node;
> + if (processing_template_decl)
> + result = NULL_TREE;
> for (tree reqs = REQUIRES_EXPR_REQS (t); reqs; reqs = TREE_CHAIN (reqs))
> {
> tree req = TREE_VALUE (reqs);
> - if (tsubst_requirement (req, args, info) == error_mark_node)
> + req = tsubst_requirement (req, args, info);
> + if (req == error_mark_node)
> {
> result = boolean_false_node;
> if (info.diagnose_unsatisfaction_p ())
> @@ -2360,7 +2388,11 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
> else
> break;
> }
> + else if (processing_template_decl)
> + result = tree_cons (NULL_TREE, req, result);
> }
> + if (processing_template_decl && result != boolean_false_node)
> + result = finish_requires_expr (EXPR_LOCATION (t), parms, nreverse (result));
> return result;
> }
>
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 9d30a271713..7dcdb5aaf7d 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -21705,7 +21705,8 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>
> case REQUIRES_EXPR:
> {
> - tree r = tsubst_requires_expr (t, args, tf_none, in_decl);
> + complain &= ~tf_warning_or_error;
> + tree r = tsubst_requires_expr (t, args, complain, in_decl);
> RETURN (r);
> }
>
> diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
> new file mode 100644
> index 00000000000..0bb11bb944c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
> @@ -0,0 +1,13 @@
> +// PR c++/112769
> +// { dg-do compile { target c++20 } }
> +
> +template<int I, typename T>
> +struct type
> +{
> + type(T) requires requires { T{0}; };
> +};
> +
> +template <typename T>
> +using alias = type<0, T>;
> +
> +alias foo{123};
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C b/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
> new file mode 100644
> index 00000000000..18974eeb172
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
> @@ -0,0 +1,25 @@
> +// PR c++/110006
> +// { dg-do compile { target c++20 } }
> +
> +template<typename T>
> +class s;
> +
> +template<typename T>
> +void constraint(s<T> const&, int&);
> +
> +template<typename U, typename T2>
> +U function(s<T2> const x)
> + requires requires (U& u) { constraint(x, u); };
> +
> +template<typename T>
> +class s
> +{
> + template<typename U, typename T2>
> + friend U function(s<T2> const x)
> + requires requires (U& u) { constraint(x, u); };
> +};
> +
> +int f(s<int> q)
> +{
> + return function<int>(q); // { dg-bogus "ambiguous" }
> +}
prev parent reply other threads:[~2024-02-02 21:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-02 19:41 Patrick Palka
2024-02-02 19:41 ` [PATCH 2/2] c++: remove lookup_template_class's entering_scope flag Patrick Palka
2024-05-01 19:41 ` Patrick Palka
2024-05-01 20:22 ` Jason Merrill
2024-05-01 20:40 ` Patrick Palka
2024-05-01 20:52 ` Jason Merrill
2024-05-02 17:49 ` Patrick Palka
2024-05-02 18:11 ` Jason Merrill
2024-02-02 19:55 ` [PATCH 1/2] c++: requires-exprs and partial constraint subst [PR112769] Jason Merrill
2024-02-02 20:01 ` Jason Merrill
2024-02-02 20:36 ` Patrick Palka
2024-02-02 20:57 ` Patrick Palka
2024-02-02 21:05 ` Jason Merrill [this message]
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