From 288e4c64f6b4806358aabc9b99b2fba72bf04bf6 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Mon, 25 Apr 2022 21:46:56 -0400 Subject: [PATCH] c++: partial ordering with dependent NTTP type [PR105289] Here ever since r11-6483-ge2e2f3f2c9400f we're rejecting and crashing on (respectively) two testcases that we used to accept in C++17 mode since r8-1437-g3da557ec145823. Both testcases declare a partial specialization of a primary template that has an NTTP with dependent type, and the validity of these partial specializations is unclear and the subject of PR86193 / CWG 455. So for now, this minimal patch just aims to fix the crash in the second testcase. During deduction, when checking whether the type of an NTTP uses still-undeduced parameters, we were incorrectly substituting into the previously substituted type instead of into its original type. In passing this patch also downgrades the "not more specialized" diagnostic from a permerror to a pedwarn. PR c++/105289 PR c++/86193 gcc/cp/ChangeLog: * pt.cc (process_partial_specialization): Downgrade "partial specialization isn't more specialized" diagnostic from permerror to an on-by-default pedwarn. (unify) : When substituting into the NTTP type a second time, use the original type not the substituted type. gcc/testsuite/ChangeLog: * g++.dg/template/partial-specialization11.C: New test. * g++.dg/template/partial-specialization12.C: New test. --- gcc/cp/pt.cc | 7 ++++--- gcc/testsuite/g++.dg/template/partial-specialization11.C | 11 +++++++++++ gcc/testsuite/g++.dg/template/partial-specialization12.C | 12 ++++++++++++ 3 files changed, 27 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/template/partial-specialization11.C create mode 100644 gcc/testsuite/g++.dg/template/partial-specialization12.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index dde62ee..7dd9e67 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -5227,8 +5227,9 @@ process_partial_specialization (tree decl) && !get_partial_spec_bindings (maintmpl, maintmpl, specargs)) { auto_diagnostic_group d; - if (permerror (input_location, "partial specialization %qD is not " - "more specialized than", decl)) + if (pedwarn (input_location, 0, + "partial specialization %qD is not more specialized than", + decl)) inform (DECL_SOURCE_LOCATION (maintmpl), "primary template %qD", maintmpl); } @@ -24299,7 +24300,7 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict, /* Now check whether the type of this parameter is still dependent, and give up if so. */ ++processing_template_decl; - tparm = tsubst (tparm, targs, tf_none, NULL_TREE); + tparm = tsubst (TREE_TYPE (parm), targs, tf_none, NULL_TREE); --processing_template_decl; if (uses_template_parms (tparm)) return unify_success (explain_p); diff --git a/gcc/testsuite/g++.dg/template/partial-specialization11.C b/gcc/testsuite/g++.dg/template/partial-specialization11.C new file mode 100644 index 0000000..556224a --- /dev/null +++ b/gcc/testsuite/g++.dg/template/partial-specialization11.C @@ -0,0 +1,11 @@ +// PR c++/86193 +// CWG 455 (active) +// { dg-options "" } // clear -pedantic-errors + +template struct value_type; + +template::type V> +struct A; + +template +struct A { }; // { dg-warning "not more specialized" } diff --git a/gcc/testsuite/g++.dg/template/partial-specialization12.C b/gcc/testsuite/g++.dg/template/partial-specialization12.C new file mode 100644 index 0000000..5f51e8a --- /dev/null +++ b/gcc/testsuite/g++.dg/template/partial-specialization12.C @@ -0,0 +1,12 @@ +// PR c++/105289 +// CWG 455 (active) +// { dg-do compile { target c++11 } } + +template +struct value_type; + +template::type Element> +struct push_front_vlist; + +template class XList, class T, T Arg, T... Vs> +struct push_front_vlist, Arg> { }; // { dg-error "not more specialized" } -- 2.7.4