Fixed the struct map interaction with serial_name. Added a separarte JSON test for serial_name.

tests/json_struct.rs

@@ -0,0 +1,31 @@
+#![feature(phase)]
+
+extern crate serde;
+#[phase(plugin)]
+extern crate serde_macros;
+
+#[deriving(PartialEq, Show)]
+#[deriving_serializable]
+#[deriving_deserializable]
+struct Test {
+    #[serial_name = "$schema"]
+    schema: String,
+    title: String,
+    #[serial_name = "type"]
+    ty: int
+}
+
+#[test]
+fn test_json_struct() {
+    let input = Test {
+        schema: "a".to_string(),
+        title: "b".to_string(),
+        ty: 3,
+    };
+
+    let s = serde::json::to_string(&input).unwrap();
+    assert_eq!(s.as_slice(), r#"{"$schema":"a","title":"b","type":3}"#);
+
+    let output: Test = serde::json::from_str(s.as_slice()).unwrap();
+    assert_eq!(input, output);
+}