From: Marek Polacek <polacek@redhat.com>
Date: Wed, 24 Jun 2026 19:59:28 +0000 (-0400)
Subject: c++/reflection: ^^ cannot define types [PR125922]
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e797f09f8bdd680620da04d925ee429ed3201e07;p=thirdparty%2Fgcc.git

c++/reflection: ^^ cannot define types [PR125922]

The reflect-expression production uses "^^ type-id" which doesn't
allow defining types (it's not defining-type-id), but we aren't
checking this.

	PR c++/125922

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_reflect_expression): Temporarily set
	parser->type_definition_forbidden_message.

gcc/testsuite/ChangeLog:

	* g++.dg/reflect/error14.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 8194106c6e9..aeff4535337 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -10147,8 +10147,13 @@ cp_parser_reflect_expression (cp_parser *parser)
   cp_parser_parse_tentatively (parser);
 
   bool type_alias_p;
-  t = cp_parser_type_id_1 (parser, CP_PARSER_FLAGS_NONE, false, false,
-			   nullptr, &type_alias_p);
+  {
+    auto tdfm =
+      make_temp_override (parser->type_definition_forbidden_message,
+			  G_("types may not be defined in %<^^%> expression"));
+    t = cp_parser_type_id_1 (parser, CP_PARSER_FLAGS_NONE, false, false,
+			     nullptr, &type_alias_p);
+  }
   if (cp_parser_parse_definitely (parser))
     {
       /* With using A = int; ^^A is a type alias but ^^const A or ^^A & or
diff --git a/gcc/testsuite/g++.dg/reflect/error14.C b/gcc/testsuite/g++.dg/reflect/error14.C
new file mode 100644
index 00000000000..e525ac92832
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/error14.C
@@ -0,0 +1,15 @@
+// PR c++/125922
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+void
+f ()
+{
+  consteval {
+    (void) ^^struct { }; // { dg-error "types may not be defined" }
+    (void) ^^struct S { }; // { dg-error "types may not be defined" }
+    (void) ^^struct A { struct B { }; }; // { dg-error "types may not be defined" }
+    (void) ^^enum E { }; // { dg-error "types may not be defined" }
+    (void) ^^union U { }; // { dg-error "types may not be defined" }
+  }
+}