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[130.44.146.16]) by smtp.gmail.com with ESMTPSA id kv2-20020a056214534200b006869485d9eesm1088613qvb.82.2024.02.02.11.55.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Feb 2024 11:55:53 -0800 (PST) Message-ID: Date: Fri, 2 Feb 2024 14:55:52 -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 , gcc-patches@gcc.gnu.org References: <20240202194104.317982-1-ppalka@redhat.com> From: Jason Merrill In-Reply-To: <20240202194104.317982-1-ppalka@redhat.com> 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=-13.3 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_H2,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 14:41, Patrick Palka wrote: > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this > look OK for trunk? OK. > -- >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. > > PR c++/112769 > PR c++/110006 > > gcc/cp/ChangeLog: > > * constraint.cc (tsubst_simple_requirement): Return a > substituted _REQ node when processing_template_decl. > (tsubst_type_requirement): Likewise. > (tsubst_compound_requirement): Likewise. > (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_baselink): Use tsubst_aggr_type with > entring_scope=true instead of tsubst to substitute > qualifying_scope. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/class-deduction-alias18.C: New test. > * g++.dg/cpp2a/concepts-friend16.C: New test. > --- > gcc/cp/constraint.cc | 38 +++++++++++++++++-- > gcc/cp/pt.cc | 3 +- > .../g++.dg/cpp2a/class-deduction-alias18.C | 13 +++++++ > .../g++.dg/cpp2a/concepts-friend16.C | 25 ++++++++++++ > 4 files changed, 74 insertions(+), 5 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..450ae548f9a 100644 > --- a/gcc/cp/constraint.cc > +++ b/gcc/cp/constraint.cc > @@ -2028,6 +2028,8 @@ 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; > } > > @@ -2068,6 +2070,8 @@ 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; > } > > @@ -2182,6 +2186,9 @@ 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; > } > > @@ -2190,6 +2197,15 @@ tsubst_compound_requirement (tree t, tree args, sat_info info) > static tree > tsubst_nested_requirement (tree t, tree args, sat_info info) > { > + 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 (tf_none, info.in_decl); > tree result = constraint_satisfaction_value (t, args, quiet); > if (result == boolean_true_node) > @@ -2330,18 +2346,25 @@ 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 +2372,13 @@ 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 +2386,11 @@ 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..17ecd4b9c5a 100644 > --- a/gcc/cp/pt.cc > +++ b/gcc/cp/pt.cc > @@ -17065,7 +17065,8 @@ tsubst_baselink (tree baselink, tree object_type, > { > bool qualified_p = BASELINK_QUALIFIED_P (baselink); > tree qualifying_scope = BINFO_TYPE (BASELINK_ACCESS_BINFO (baselink)); > - qualifying_scope = tsubst (qualifying_scope, args, complain, in_decl); > + qualifying_scope = tsubst_aggr_type (qualifying_scope, args, complain, in_decl, > + /*entering_scope=*/true); > > tree optype = BASELINK_OPTYPE (baselink); > optype = tsubst (optype, args, complain, in_decl); > 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" } > +}