parse comma separated lists (somewhat) properly

src/value/parse.rs

@@ -92,8 +92,14 @@ impl Value {
                     Ok(x) => x,
                     Err(_) => return Ok(left),
                 };
+                if let Value::List(v, ListSeparator::Comma) = right {
+                    let mut v2 = vec![left];
+                    v2.extend(v);
+                    Ok(Value::List(v2, ListSeparator::Comma))
+                } else {
                     Ok(Value::List(vec![left, right], ListSeparator::Comma))
                 }
+            }
             TokenKind::Symbol(Symbol::Plus)
             | TokenKind::Symbol(Symbol::Minus)
             | TokenKind::Op(_)

tests/list.rs

@@ -0,0 +1,20 @@
+#![cfg(test)]
+
+#[macro_use]
+mod macros;
+
+test!(
+    length_of_list_as_var,
+    "$a: 1 2 3 4 5;a {\n  color: length($a);\n}\n",
+    "a {\n  color: 5;\n}\n"
+);
+test!(
+    length_of_list,
+    "a {\n  color: length(1 2 3 4 5);\n}\n",
+    "a {\n  color: 5;\n}\n"
+);
+test!(
+    length_of_comma_list,
+    "a {\n  color: length((1, 2, 3, 4, 5));\n}\n",
+    "a {\n  color: 5;\n}\n"
+);

tests/values.rs

@@ -463,13 +463,3 @@ test!(
     "a {\n  color: (a b) - (1 2);\n}\n",
     "a {\n  color: a b-1 2;\n}\n"
 );
-test!(
-    length_of_list_as_var,
-    "$a: 1 2 3 4 5;a {\n  color: length($a);\n}\n",
-    "a {\n  color: 5;\n}\n"
-);
-test!(
-    length_of_list,
-    "a {\n  color: length(1 2 3 4 5);\n}\n",
-    "a {\n  color: 5;\n}\n"
-);