{"id":2221615,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2221615/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260410002735.1424952-1-polacek@redhat.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.1/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null},"msgid":"<20260410002735.1424952-1-polacek@redhat.com>","date":"2026-04-10T00:27:35","name":"c++/reflection: fn call with splice in decltype rejected [PR124835]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"9dde63f88309a8b7ea7004f4c63422ba2232f236","submitter":{"id":14370,"url":"http://patchwork.ozlabs.org/api/1.1/people/14370/?format=json","name":"Marek Polacek","email":"polacek@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260410002735.1424952-1-polacek@redhat.com/mbox/","series":[{"id":499372,"url":"http://patchwork.ozlabs.org/api/1.1/series/499372/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=499372","date":"2026-04-10T00:27:35","name":"c++/reflection: fn call with splice in decltype rejected [PR124835]","version":1,"mbox":"http://patchwork.ozlabs.org/series/499372/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2221615/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2221615/checks/","tags":{},"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=OR8wA7lq;\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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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1775780865;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:mime-version:mime-version:content-type:content-type:\n content-transfer-encoding:content-transfer-encoding;\n bh=W4Ln+THW6aTWToF9QslA0M1uajkJvBgJlmS+COluNfg=;\n b=OR8wA7lqFRZJQgZglW8OI50iiGRDbYSDLZI6Wj9fM689zO2X6rj/jU/kYlD8n91TiLtWH+\n SadLTaIHL7U8etOJL0G8pzrsqWW95nV7TrUuOhsHGyH9TLautVfWlmVgIF4cDkoNwbbvAy\n JBsugESrGionaXahd4J0t1VphyELyKY=","X-MC-Unique":"v16PGviRNrm9_KMKoc0uIw-1","X-Mimecast-MFC-AGG-ID":"v16PGviRNrm9_KMKoc0uIw_1775780861","From":"Marek Polacek ","To":"GCC Patches ,\n\tJason Merrill ","Subject":"[PATCH] c++/reflection: fn call with splice in decltype rejected\n [PR124835]","Date":"Thu, 9 Apr 2026 20:27:35 -0400","Message-ID":"<20260410002735.1424952-1-polacek@redhat.com>","MIME-Version":"1.0","X-Scanned-By":"MIMEDefang 3.4.1 on 10.30.177.93","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"mqxIb-oBqryMKvdguLwFkZO4wWD6sxeiI8TYn2tOsLM_1775780861","X-Mimecast-Originator":"redhat.com","Content-Transfer-Encoding":"8bit","content-type":"text/plain; charset=\"US-ASCII\"; x-default=true","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"I found this while working on the mangling patch and this bug\nblocks that patch.\n\nBootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?\n\n-- >8 --\nHere we reject the valid\n\n decltype([:^^foo:](42))\n\nsaying that a ')' is expected. [dcl.type.decltype] says \"if E is an\nunparenthesized splice-expression, decltype(E) is...\" and we handle it\nby calling _splice_expression and setting id_expression_or_member_access_p.\n\nBut for the code above we shouldn't do this, because the [: :] isn't\nthe sole operand of decltype. _nth_token_starts_splice_without_nns_p\nchecks that there's no :: after the :] but here we want to check that\nthe [: :] is followed by a ')'.\n\n\tPR c++/124835\n\ngcc/cp/ChangeLog:\n\n\t* parser.cc (cp_parser_decltype_expr): Check that [: :] is\n\tfollowed by a ')' before declaring it an unparenthesized\n\tsplice-expression.\n\ngcc/testsuite/ChangeLog:\n\n\t* g++.dg/reflect/decltype2.C: New test.\n---\n gcc/cp/parser.cc | 11 ++++++++++-\n gcc/testsuite/g++.dg/reflect/decltype2.C | 12 ++++++++++++\n 2 files changed, 22 insertions(+), 1 deletion(-)\n create mode 100644 gcc/testsuite/g++.dg/reflect/decltype2.C\n\n\nbase-commit: 9772e8d3c2dd45195ec6d0d0c00f533d976ac249","diff":"diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc\nindex fe27a15a283..6493a26a149 100644\n--- a/gcc/cp/parser.cc\n+++ b/gcc/cp/parser.cc\n@@ -19387,7 +19387,16 @@ cp_parser_decltype_expr (cp_parser *parser,\n /* [dcl.type.decltype] \"if E is an unparenthesized splice-expression,\n \t decltype(E) is the type of the entity, object, or value designated\n \t by the splice-specifier of E\" */\n- if (cp_parser_nth_token_starts_splice_without_nns_p (parser, 1))\n+ const bool unparenthesized_splice_expr_p = [&] {\n+\t/* The next token must be '[:'. */\n+\tif (cp_lexer_next_token_is_not (parser->lexer, CPP_OPEN_SPLICE))\n+\t return false;\n+\t/* Skip to the end of the ':]' and see if the closing ')' follows. */\n+\tsaved_token_sentinel toks (parser->lexer, STS_ROLLBACK);\n+\treturn (cp_parser_skip_entire_splice_expr (parser)\n+\t\t&& cp_lexer_next_token_is (parser->lexer, CPP_CLOSE_PAREN));\n+ } ();\n+ if (unparenthesized_splice_expr_p)\n \t{\n \t cp_id_kind idk;\n \t expr = cp_parser_splice_expression (parser, /*template_p=*/false,\ndiff --git a/gcc/testsuite/g++.dg/reflect/decltype2.C b/gcc/testsuite/g++.dg/reflect/decltype2.C\nnew file mode 100644\nindex 00000000000..cc5532c7957\n--- /dev/null\n+++ b/gcc/testsuite/g++.dg/reflect/decltype2.C\n@@ -0,0 +1,12 @@\n+// PR c++/124835\n+// { dg-do compile { target c++26 } }\n+// { dg-additional-options \"-freflection\" }\n+\n+template\n+constexpr T foo (T t) { return t; }\n+\n+int bar (int);\n+\n+static_assert ([:^^foo:](42) == 42);\n+decltype([:^^foo:](42)) a = 42;\n+decltype([:^^foo:]) &b = bar;\n","prefixes":[]}