arginfo soft-breaks with namespaced class return type if the class name starts with N

[nielsdos]

Description

Make the following change on master to the test.stub.php file:

diff --git a/ext/zend_test/test.stub.php b/ext/zend_test/test.stub.php
index cc76a3a739..fe7a8a0ce2 100644
--- a/ext/zend_test/test.stub.php
+++ b/ext/zend_test/test.stub.php
@@ -267,6 +267,8 @@ class Foo {
         public function method(): void {}
     }
 
+    class Node {}
+
     function namespaced_func(): bool {}
 
     /** @deprecated */
@@ -280,6 +282,8 @@ function namespaced_aliased_func(): void {}
      * @alias zend_test_void_return
      */
     function namespaced_deprecated_aliased_func(): void {}
+
+    function breaks(): Node {}
 }
 
 namespace ZendTestNS2\ZendSubNS {

Now regenerate the arginfo.
Now configure using: CC=clang CXX=clang++ ./configure --enable-debug --enable-zend-test --enable-werror which is the same compiler and same --enable-werror flag that ASAN CI uses.
Now make and you'll get:

ext/zend_test/test_arginfo.h:153:86: error: incomplete universal character name; treating as '\' followed by identifier [-Werror,-Wunicode]
ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_ZendTestNS2_breaks, 0, 0, ZendTestNS2\\Node, 0)

I actually ran into this in my PR #12111 causing the ASAN build to fail.

cc @kocsismate

PHP Version

8.0+

Operating System

No response

[kocsismate]

Thank you, I'm on it!

[kocsismate]

Related to #9154. The fix is on its way :)