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[130.44.146.16]) by smtp.gmail.com with ESMTPSA id q15-20020ad4434f000000b00685191beaa9sm1151013qvs.3.2024.02.02.13.05.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Feb 2024 13:05:49 -0800 (PST) Message-ID: <124440ff-6522-44b7-96a6-803a1840d4b7@redhat.com> Date: Fri, 2 Feb 2024 16:05:48 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] c++: requires-exprs and partial constraint subst [PR112769] To: Patrick Palka Cc: gcc-patches@gcc.gnu.org References: <20240202194104.317982-1-ppalka@redhat.com> <5f06be77-2314-65e4-a242-b84059bebfbe@idea> <720eaacc-cd6a-8a66-e057-752c6a21183d@idea> From: Jason Merrill In-Reply-To: <720eaacc-cd6a-8a66-e057-752c6a21183d@idea> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,RCVD_IN_SORBS_WEB,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: 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) : 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 %", 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 > +struct type > +{ > + type(T) requires requires { T{0}; }; > +}; > + > +template > +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 > +class s; > + > +template > +void constraint(s const&, int&); > + > +template > +U function(s const x) > + requires requires (U& u) { constraint(x, u); }; > + > +template > +class s > +{ > + template > + friend U function(s const x) > + requires requires (U& u) { constraint(x, u); }; > +}; > + > +int f(s q) > +{ > + return function(q); // { dg-bogus "ambiguous" } > +}