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[69.125.73.58]) by smtp.gmail.com with ESMTPSA id bk7sm182467qkb.72.2021.11.10.08.53.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Nov 2021 08:53:11 -0800 (PST) To: gcc-patches@gcc.gnu.org Subject: [PATCH] c++: template-id ADL and partial instantiation [PR99911] Date: Wed, 10 Nov 2021 11:53:07 -0500 Message-Id: <20211110165307.4079746-1-ppalka@redhat.com> X-Mailer: git-send-email 2.34.0.rc1.14.g88d915a634 In-Reply-To: <20211103160419.1472321-1-ppalka@redhat.com> References: <20211103160419.1472321-1-ppalka@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-16.0 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_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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-Patchwork-Original-From: Patrick Palka via Gcc-patches From: Patrick Palka Reply-To: Patrick Palka Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" Here when partially instantiating the call get(T{}) with T=N::A (for which earlier unqualified name lookup for 'get' found nothing) the arguments after substitution are no longer dependent but the callee still is, so perform_koenig_lookup postpones ADL. But then we go on to diagnose the unresolved template name anyway, as if ADL was already performed and failed. This patch fixes this by avoiding the error path in question when the template arguments of an unresolved template-id are dependent, which mirrors the dependence check in perform_koenig_lookup. In passing, this patch also disables the -fpermissive fallback that performs a second unqualified lookup in the template-id ADL case; this fallback seems to be intended for legacy code and shouldn't be used for C++20 template-id ADL. Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk and perhaps 11? PR c++/99911 gcc/cp/ChangeLog: * pt.c (tsubst_copy_and_build) : Don't diagnose name lookup failure if the arguments to an unresolved template name are still dependent. Disable the -fpermissive fallback for template-id ADL. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/fn-template24.C: New test. --- gcc/cp/pt.c | 6 ++++-- gcc/testsuite/g++.dg/cpp2a/fn-template24.C | 16 ++++++++++++++++ 2 files changed, 20 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/fn-template24.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 991a20a85d4..4beddf9caf8 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -20427,12 +20427,14 @@ tsubst_copy_and_build (tree t, if (function != NULL_TREE && (identifier_p (function) || (TREE_CODE (function) == TEMPLATE_ID_EXPR - && identifier_p (TREE_OPERAND (function, 0)))) + && identifier_p (TREE_OPERAND (function, 0)) + && !any_dependent_template_arguments_p (TREE_OPERAND + (function, 1)))) && !any_type_dependent_arguments_p (call_args)) { if (TREE_CODE (function) == TEMPLATE_ID_EXPR) function = TREE_OPERAND (function, 0); - if (koenig_p && (complain & tf_warning_or_error)) + else if (koenig_p && (complain & tf_warning_or_error)) { /* For backwards compatibility and good diagnostics, try the unqualified lookup again if we aren't in SFINAE diff --git a/gcc/testsuite/g++.dg/cpp2a/fn-template24.C b/gcc/testsuite/g++.dg/cpp2a/fn-template24.C new file mode 100644 index 00000000000..b444ac6a273 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/fn-template24.C @@ -0,0 +1,16 @@ +// PR c++/99911 +// { dg-do compile { target c++20 } } + +namespace N { + struct A { }; + template void get(A); +}; + +template +auto f() { + return [](U) { get(T{}); }; +} + +int main() { + f()(0); +}