Fixed XML encoding, add equality comparisons to Optional<T>

DataTypes/Optional.cs

@@ -1,4 +1,6 @@
-namespace RobloxFiles.DataTypes
+using System;
+
+namespace RobloxFiles.DataTypes
 {
     // Optional represents a value that can be explicitly
     // marked as an optional variant to a specified type.
@@ -19,6 +21,29 @@
             return Value?.ToString() ?? "null";
         }
 
+        public override int GetHashCode()
+        {
+            if (HasValue)
+                return Value.GetHashCode();
+
+            var T = typeof(T);
+            return T.GetHashCode();
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is Optional<T> optional))
+                return false;
+
+            if (HasValue != optional.HasValue)
+                return false;
+
+            if (HasValue)
+                return Value.Equals(optional.Value);
+
+            return true; // Both have no value.
+        }
+
         public static implicit operator T(Optional<T> optional)
         {
             if (optional.HasValue)

Tree/Instance.cs

@@ -644,6 +644,14 @@ namespace RobloxFiles
                             xmlToken = "CoordinateFrame";
                             break;
                         }
+                        case "Optional`1":
+                        {
+                            // TODO: If more optional types are added,
+                            //       this needs disambiguation.
+
+                            xmlToken = "OptionalCoordinateFrame";
+                            break;
+                        }
                     }
 
                     if (!props.ContainsKey(fieldName))