Add a test to confirm that #357 is fixed (#477)

Add a test to confirm that #357 is fixed

tests/357_untagged_enum_roundtrip.rs

@@ -0,0 +1,36 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(untagged)]
+enum MyValue {
+    Int(i64),
+    String(String),
+    Enum(Enum),
+    List(Vec<MyValue>),
+}
+
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
+enum Enum {
+    First(String),
+    Second(i64),
+}
+
+#[test]
+fn untagged_enum_not_a_list() {
+    // Contributed by @obi1kenobi in https://github.com/ron-rs/ron/issues/357
+
+    let value = MyValue::Enum(Enum::First("foo".to_string()));
+
+    let ron = ron::to_string(&value).unwrap();
+    assert_eq!(ron, "First(\"foo\")");
+
+    let de = ron::from_str(&ron).unwrap();
+
+    // This used to fail as the value was deserialised as `List([String("foo")])`
+    assert_eq!(
+        value,
+        de,
+        "Serialized as: {}",
+        ron::to_string(&value).unwrap()
+    );
+}