From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1734) id A52A8385842D; Fri, 17 Dec 2021 18:08:41 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A52A8385842D MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Marek Polacek To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-6049] c++: Improve diagnostic for class tmpl/class redecl [PR103749] X-Act-Checkin: gcc X-Git-Author: Marek Polacek X-Git-Refname: refs/heads/trunk X-Git-Oldrev: 87ae8d7613a8b15d0d729b38ffd49153f1314799 X-Git-Newrev: fae016862631da70e6482fe3173a111248f8b9bc Message-Id: <20211217180841.A52A8385842D@sourceware.org> Date: Fri, 17 Dec 2021 18:08:41 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Dec 2021 18:08:41 -0000 https://gcc.gnu.org/g:fae016862631da70e6482fe3173a111248f8b9bc commit r12-6049-gfae016862631da70e6482fe3173a111248f8b9bc Author: Marek Polacek Date: Thu Dec 16 14:57:07 2021 -0500 c++: Improve diagnostic for class tmpl/class redecl [PR103749] For code like template struct bar; struct bar { int baz; }; bar var; we emit a fairly misleading and unwieldy diagnostic: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ g++ -c u.cc u.cc:6:8: error: template argument required for 'struct bar' 6 | struct bar { | ^~~ u.cc:10:5: error: class template argument deduction failed: 10 | bar var; | ^~~ u.cc:10:5: error: no matching function for call to 'bar()' u.cc:3:17: note: candidate: 'template bar()-> bar< >' 3 | friend struct bar; | ^~~ u.cc:3:17: note: template argument deduction/substitution failed: u.cc:10:5: note: couldn't deduce template parameter '' 10 | bar var; | ^~~ u.cc:3:17: note: candidate: 'template bar(bar< >)-> bar< >' 3 | friend struct bar; | ^~~ u.cc:3:17: note: template argument deduction/substitution failed: u.cc:10:5: note: candidate expects 1 argument, 0 provided 10 | bar var; | ^~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ but with this patch we get: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ z.C:4:10: error: class template 'bar' redeclared as non-template 4 | struct bar { | ^~~ z.C:2:10: note: previous declaration here 2 | struct bar; | ^~~ z.C:8:7: error: 'bar<...auto...> var' has incomplete type 8 | bar var; | ^~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ which is clearer about what the problem is. I thought it'd be nice to avoid printing the messages about failed CTAD, too. To that end, I'm using CLASSTYPE_ERRONEOUS to suppress CTAD. Not sure if that's entirely kosher. The other direction (first a non-template class declaration followed by a class template definition) we handle quite well: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ z.C:11:8: error: 'bar' is not a template 11 | struct bar {}; | ^~~ z.C:8:8: note: previous declaration here 8 | struct bar; | ^~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PR c++/103749 gcc/cp/ChangeLog: * decl.c (lookup_and_check_tag): Give an error when a class was declared as template but no template header has been provided. * pt.c (do_class_deduction): Don't deduce CLASSTYPE_ERRONEOUS types. gcc/testsuite/ChangeLog: * g++.dg/template/redecl4.C: Adjust dg-error. * g++.dg/diagnostic/redeclaration-2.C: New test. Diff: --- gcc/cp/decl.c | 10 ++++++++++ gcc/cp/pt.c | 7 +++++++ gcc/testsuite/g++.dg/diagnostic/redeclaration-2.C | 19 +++++++++++++++++++ gcc/testsuite/g++.dg/template/redecl4.C | 2 +- 4 files changed, 37 insertions(+), 1 deletion(-) diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 7ca8770bd02..982fca8983d 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -15438,6 +15438,16 @@ lookup_and_check_tag (enum tag_types tag_code, tree name, return error_mark_node; } + if (DECL_CLASS_TEMPLATE_P (decl) + && !template_header_p + && how == TAG_how::CURRENT_ONLY) + { + error ("class template %qD redeclared as non-template", name); + inform (location_of (decl), "previous declaration here"); + CLASSTYPE_ERRONEOUS (TREE_TYPE (decl)) = true; + return error_mark_node; + } + if (DECL_CLASS_TEMPLATE_P (decl) /* If scope is TAG_how::CURRENT_ONLY we're defining a class, so ignore a template template parameter. */ diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 18c6f118ae6..4f0ae6d5851 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -29601,6 +29601,13 @@ do_class_deduction (tree ptype, tree tmpl, tree init, if (DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl)) return ptype; + /* If the class was erroneous, don't try to deduce, because that + can generate a lot of diagnostic. */ + if (TREE_TYPE (tmpl) + && TYPE_LANG_SPECIFIC (TREE_TYPE (tmpl)) + && CLASSTYPE_ERRONEOUS (TREE_TYPE (tmpl))) + return ptype; + /* Wait until the enclosing scope is non-dependent. */ if (DECL_CLASS_SCOPE_P (tmpl) && dependent_type_p (DECL_CONTEXT (tmpl))) diff --git a/gcc/testsuite/g++.dg/diagnostic/redeclaration-2.C b/gcc/testsuite/g++.dg/diagnostic/redeclaration-2.C new file mode 100644 index 00000000000..4423e12b0b1 --- /dev/null +++ b/gcc/testsuite/g++.dg/diagnostic/redeclaration-2.C @@ -0,0 +1,19 @@ +// PR c++/103749 + +struct foo { + template + friend struct bar; +}; + +struct bar { // { dg-error "redeclared as non-template" } + int baz; +}; + +template +struct T; // { dg-message "previous" } + +struct T { // { dg-error "redeclared as non-template" } +}; + +bar var; // { dg-error "" } +T t; // { dg-error "" } diff --git a/gcc/testsuite/g++.dg/template/redecl4.C b/gcc/testsuite/g++.dg/template/redecl4.C index 5638bde413d..c9282cde860 100644 --- a/gcc/testsuite/g++.dg/template/redecl4.C +++ b/gcc/testsuite/g++.dg/template/redecl4.C @@ -2,4 +2,4 @@ // { dg-do compile } template union A; // { dg-message "previous" } -struct A; // { dg-error "non-template" } +struct A; // { dg-error "redeclared as non-template" }