Expand upgrading note for namespaced name change

Mention the case from bug #79942.

[ci skip]

diff --git a/UPGRADING b/UPGRADING
index 15e19f27822ec09543db50744ee623127b93f6a7..c74fc585ad3c4a8c4eaf9268c4b832d9f58c733d 100644 (file)
--- a/UPGRADING
+++ b/UPGRADING
@@ -206,7 +206,9 @@ PHP 8.0 UPGRADE NOTES
     RFC: https://wiki.php.net/rfc/string_to_number_comparison
   . Namespaced names can no longer contain whitespace: While `Foo\Bar` will be
     recognized as a namespaced name, `Foo \ Bar` will not. Conversely, reserved
-    keywords are now permitted as namespace segments.
+    keywords are now permitted as namespace segments, which may also change the
+    interpretation of code: `new\x` is now the same as `constant('new\x')`, not
+    `new \x()`.
     RFC: https://wiki.php.net/rfc/namespaced_names_as_token
   . Nested ternaries now require explicit parentheses.
     RFC: https://wiki.php.net/rfc/ternary_associativity