Handle empty lists ()

src/value/parse.rs

@@ -191,6 +191,10 @@ impl Value {
             }
             TokenKind::Symbol(Symbol::OpenParen) => {
                 devour_whitespace_or_comment(toks);
+                if toks.peek().unwrap().is_symbol(Symbol::CloseParen) {
+                    toks.next();
+                    return Ok(Value::List(Vec::new(), ListSeparator::Space));
+                }
                 let val = Self::from_tokens(toks, scope, super_selector)?;
                 assert_eq!(
                     toks.next().unwrap().kind,

tests/list.rs

@@ -105,3 +105,13 @@ test!(
     "a {\n  color: append((a, b), c, space);\n}\n",
     "a {\n  color: a b c;\n}\n"
 );
+test!(
+    list_separator_empty,
+    "a {\n  color: list-separator(());\n}\n",
+    "a {\n  color: space;\n}\n"
+);
+test!(
+    append_empty,
+    "a {\n  color: append((), a);\n}\n",
+    "a {\n  color: a;\n}\n"
+);

tests/meta.rs

@@ -129,6 +129,11 @@ test!(
     "a {\n  color: type-of(red)\n}\n",
     "a {\n  color: color;\n}\n"
 );
+test!(
+    type_of_empty_list,
+    "a {\n  color: type-of(())\n}\n",
+    "a {\n  color: list;\n}\n"
+);
 test!(
     type_of_spaced_list,
     "a {\n  color: type-of(1 2 3)\n}\n",