[{"id":3679980,"web_url":"http://patchwork.ozlabs.org/comment/3679980/","msgid":"","list_archive_url":null,"date":"2026-04-21T16:53:38","subject":"Re: [PATCH] c++: Parse splice-type-specifier in\n cp_parser_mem_initializer_id [PR124944]","submitter":{"id":4337,"url":"http://patchwork.ozlabs.org/api/people/4337/","name":"Jason Merrill","email":"jason@redhat.com"},"content":"On 4/21/26 2:21 AM, Jakub Jelinek wrote:\n> Hi!\n> \n> The grammar has:\n> mem-initializer-id:\n> \tclass-or-decltype\n> \tidentifier\n> class-or-decltype:\n> \tnested-name-specifier[opt] type-name\n> \tnested-name-specifier template simple-template-id\n> \tcomputed-type-specifier\n> computed-type-specifier:\n> \tdecltype-specifier\n> \tpack-index-specifier\n> \tsplice-type-specifier\n> but we weren't parsing splice-type-specifier in there, just in\n> cp_parser_base_specifier. So, the following patch defers\n> similarly to cp_parser_base_specifier the typename diagnostics\n> because we don't know whether typename [: will be valid or not\n> - it could be splice-scope-specifier and in that case typename\n> is not valid, or splice-type-specifier, in which case it is valid\n> but not required. And calls cp_parser_splice_type_specifier too\n> when nested-name-specifier nor :: don't appear.\n> \n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\nOK.\n\n> 2026-04-21 Jakub Jelinek \n> \n> \tPR c++/124944\n> \t* parser.cc (cp_parser_mem_initializer_id): Parse\n> \tsplice-type-specifier.\n> \n> \t* g++.dg/reflect/splice13.C: New test.\n> \t* g++.dg/reflect/splice14.C: New test.\n> \n> --- gcc/cp/parser.cc.jj\t2026-04-16 18:56:51.665066851 +0200\n> +++ gcc/cp/parser.cc\t2026-04-20 20:14:17.454246322 +0200\n> @@ -19974,14 +19974,17 @@ cp_parser_mem_initializer_id (cp_parser*\n> bool template_p = false;\n> tree id;\n> \n> - cp_token *token = cp_lexer_peek_token (parser->lexer);\n> + cp_token *typename_token = nullptr, *splice_token = nullptr;\n> \n> - /* `typename' is not allowed in this context ([temp.res]). */\n> + /* `typename' is not allowed in this context ([temp.res]), unless\n> + it is part of splice-type-specifier. Defer diagnostics for now\n> + because it needs to be diagnosed if followed by splice-scope-specifier\n> + but not when followed by splice-type-specifier. */\n> if (cp_lexer_next_token_is_keyword (parser->lexer, RID_TYPENAME))\n> {\n> - error_at (token->location,\n> -\t\t\"keyword % not allowed in this context (a qualified \"\n> -\t\t\"member initializer is implicitly a type)\");\n> + typename_token = cp_lexer_peek_token (parser->lexer);\n> + if (cp_parser_next_tokens_start_splice_type_spec_p (parser, true))\n> +\tsplice_token = cp_lexer_peek_nth_token (parser->lexer, 2);\n> cp_lexer_consume_token (parser->lexer);\n> }\n> /* Look for the optional `::' operator. */\n> @@ -20008,6 +20011,12 @@ cp_parser_mem_initializer_id (cp_parser*\n> \t\t\t\t\t /*type_p=*/true,\n> \t\t\t\t\t /*is_declaration=*/true)\n> != NULL_TREE);\n> + if (typename_token && cp_lexer_peek_token (parser->lexer) != splice_token)\n> + /* Emit deferred diagnostics for invalid typename keyword if\n> + cp_parser_nested_name_specifier_opt parsed splice-scope-specifier. */\n> + error_at (typename_token->location,\n> +\t \"keyword % not allowed in this context (a qualified \"\n> +\t \"member initializer is implicitly a type)\");\n> if (nested_name_specifier_p)\n> template_p = cp_parser_optional_template_keyword (parser);\n> /* If there is a `::' operator or a nested-name-specifier, then we\n> @@ -20020,6 +20029,14 @@ cp_parser_mem_initializer_id (cp_parser*\n> \t\t\t\t /*check_dependency_p=*/true,\n> \t\t\t\t /*class_head_p=*/false,\n> \t\t\t\t /*is_declaration=*/true);\n> + else if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_SPLICE))\n> + {\n> + /* Parse C++26 splice-type-specifier. */\n> + id = cp_parser_splice_type_specifier (parser);\n> + if (id == NULL_TREE)\n> +\treturn error_mark_node;\n> + return id;\n> + }\n> /* Otherwise, we could also be looking for an ordinary identifier. */\n> cp_parser_parse_tentatively (parser);\n> if (cp_lexer_next_token_is_decltype (parser->lexer))\n> --- gcc/testsuite/g++.dg/reflect/splice13.C.jj\t2026-04-20 20:17:23.199120525 +0200\n> +++ gcc/testsuite/g++.dg/reflect/splice13.C\t2026-04-20 20:16:47.095728081 +0200\n> @@ -0,0 +1,23 @@\n> +// PR c++/124944\n> +// { dg-do compile { target c++26 } }\n> +// { dg-additional-options \"-freflection\" }\n> +\n> +struct A {};\n> +constexpr auto x = ^^A;\n> +\n> +struct B : [: x :] {\n> + B () : typename [: x :] () {}\n> +};\n> +\n> +struct C : [: x :] {\n> + C () : [: x :] () {}\n> +};\n> +\n> +namespace D {\n> + struct E {};\n> +}\n> +constexpr auto y = ^^D;\n> +\n> +struct F : [: y :]::E {\n> + F () : [: y :]::E () {}\n> +};\n> --- gcc/testsuite/g++.dg/reflect/splice14.C.jj\t2026-04-20 20:17:30.732993744 +0200\n> +++ gcc/testsuite/g++.dg/reflect/splice14.C\t2026-04-20 20:20:51.386617097 +0200\n> @@ -0,0 +1,12 @@\n> +// PR c++/124944\n> +// { dg-do compile { target c++26 } }\n> +// { dg-additional-options \"-freflection\" }\n> +\n> +namespace D {\n> + struct E {};\n> +}\n> +constexpr auto y = ^^D;\n> +\n> +struct F : [: y :]::E {\n> + F () : typename [: y :]::E () {}\t// { dg-error \"keyword 'typename' not allowed in this context \\\\\\(a qualified member initializer is implicitly a type\\\\\\)\" }\n> +};\n> \n> \tJakub\n>","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=ECj/FNXq;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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