handle ! at toplevel

src/stylesheet.rs

@@ -295,7 +295,7 @@ impl<'a> StyleSheetParser<'a> {
                 c if c.is_control() => {
                     return Err(("expected selector.", self.lexer.next().unwrap().pos()).into());
                 }
-                ',' => {
+                ',' | '!' => {
                     return Err(("expected \"{\".", self.lexer.next().unwrap().pos()).into());
                 }
                 _ => todo!("unexpected toplevel token: {:?}", kind),

tests/error.rs

@@ -86,3 +86,7 @@ error!(
     toplevel_comma,
     "a {},", "Error: expected \"{\"."
 );
+error!(
+    toplevel_exclamation,
+    "! {}", "Error: expected \"{\"."
+);