From 86cb4a7ec793902ae70508c3a2931fa66d361e39 Mon Sep 17 00:00:00 2001
From: Nick Logan <nlogan@gmail.com>
Date: Tue, 8 Sep 2026 07:20:51 -0700
Subject: [PATCH] Backtrack explicitly across an optional namespace prefix

The optional prefix ident matches the `url` of `url(...)`, and the rule
only parses because it then backtracks to give the prefix up. That only
works because a quantifier followed by whitespace in a rule is currently
not ratcheted, which rakudo may change in the future. `?!` asks for the
backtracking explicitly, so the rule keeps parsing either way.
---
 lib/CSS/Module/CSS3/Namespaces.rakumod | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/CSS/Module/CSS3/Namespaces.rakumod b/lib/CSS/Module/CSS3/Namespaces.rakumod
index af6aa8f8..a6e36672 100644
--- a/lib/CSS/Module/CSS3/Namespaces.rakumod
+++ b/lib/CSS/Module/CSS3/Namespaces.rakumod
@@ -6,7 +6,7 @@ use v6;
 
 unit class CSS::Module::CSS3::Namespaces;
 
-rule at-decl:sym<namespace> {'@'(:i'namespace') <ns-prefix=.Ident>? [<url=.url-string>|<url>] ';' }
+rule at-decl:sym<namespace> {'@'(:i'namespace') <ns-prefix=.Ident>?! [<url=.url-string>|<url>] ';' }
 
 class Actions {
     use CSS::Grammar::Defs :CSSObject;