Compare updated template evaluator (#4092)

src/Sdk/Expressions/Data/ExpressionData.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace GitHub.Actions.Expressions.Data
+{
+    /// <summary>
+    /// Base class for all template tokens
+    /// </summary>
+    [DataContract]
+    [JsonConverter(typeof(ExpressionDataJsonConverter))]
+    public abstract class ExpressionData
+    {
+        protected ExpressionData(Int32 type)
+        {
+            Type = type;
+        }
+
+        [DataMember(Name = "t", EmitDefaultValue = false)]
+        internal Int32 Type { get; }
+
+        public abstract ExpressionData Clone();
+
+        public abstract JToken ToJToken();
+    }
+}