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[130.44.159.43]) by smtp.gmail.com with ESMTPSA id y5-20020a37f605000000b0069ffe63228fsm9609197qkj.121.2022.05.31.12.02.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 May 2022 12:02:43 -0700 (PDT) Message-ID: <1fe00521-20fb-5673-7a00-1d3dc28def56@redhat.com> Date: Tue, 31 May 2022 15:02:42 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] c++: don't substitute TEMPLATE_PARM_CONSTRAINT [PR100374] To: Patrick Palka Cc: gcc-patches@gcc.gnu.org References: <20220527180543.2908762-1-ppalka@redhat.com> <89dc1f48-0c65-a4e7-8791-3d541e074bb7@redhat.com> <9366f773-368b-2957-c3ff-0fb8d17c240d@idea> From: Jason Merrill In-Reply-To: <9366f773-368b-2957-c3ff-0fb8d17c240d@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: 8bit X-Spam-Status: No, score=-12.5 required=5.0 tests=BAYES_00, BODY_8BITS, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, 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 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 31 May 2022 19:02:55 -0000 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 struct A { template U f(U) requires C; template U f(U) requires C; }; // Substitute int for T in above requirements to find match. template <> template U A::f(U) requires C { } >>>>     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 >>>> +concept C = true; >>>> + >>>> +template >>>> +struct A { >>>> +  template U> >>>> +  void f(); >>>> + >>>> +  template U> >>>> +  struct B; >>>> +}; >>>> + >>>> +template struct A; >>> >>