handle maps in nth()

src/builtin/list.rs

@@ -26,6 +26,7 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
             max_args!(args, 2);
             let list = match arg!(args, 0, "list") {
                 Value::List(v, ..) => v,
+                Value::Map(m) => m.entries(),
                 v => vec![v],
             };
             let n = match arg!(args, 1, "n") {

src/value/map.rs

@@ -2,6 +2,7 @@ use std::slice::Iter;
 use std::vec::IntoIter;
 
 use super::Value;
+use crate::common::{Brackets, ListSeparator};
 use crate::error::SassResult;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -48,6 +49,13 @@ impl SassMap {
         self.0.into_iter().map(|(.., v)| v).collect()
     }
 
+    pub fn entries(self) -> Vec<Value> {
+        self.0
+            .into_iter()
+            .map(|(k, v)| Value::List(vec![k, v], ListSeparator::Space, Brackets::None))
+            .collect()
+    }
+
     pub fn insert(&mut self, key: Value, value: Value) {
         for &mut (ref k, ref mut v) in &mut self.0 {
             if k == &key {

tests/list.rs

@@ -38,6 +38,11 @@ test!(
     "a {\n  color: nth(foo, 1);\n}\n",
     "a {\n  color: foo;\n}\n"
 );
+test!(
+    nth_map,
+    "a {\n  color: nth((c: d, e: f, g: h), 2);\n}\n",
+    "a {\n  color: e f;\n}\n"
+);
 test!(
     list_separator_space_separated,
     "a {\n  color: list-separator(a b c);\n}\n",