[Fix] StackItem.GetHashCode for CompoundType (#3549)

* Fixed #3544

* Fixed SubItems of CompoundType

* Reused `Unsafe.HashBytes` for hashing function in compoundtype

* Fixed test

* simple hashcode for compoundtype

* Test circular reference

* Fixed compoundType

* Add one more test case

* Fixed test

* changed to use subclass

* add comment

* Add more to GetHashCode for CompoundType

* Clean code

---------

Co-authored-by: Jimmy <[email protected]>
Co-authored-by: Fernando Diaz Toledano <[email protected]>
Co-authored-by: NGD Admin <[email protected]>

src/Neo.VM/Types/CompoundType.cs

@@ -60,12 +60,32 @@ public sealed override bool GetBoolean()
         }
 
         /// <summary>
-        /// The operation is not supported. Always throw <see cref="NotSupportedException"/>.
+        ///
+        /// This method provides a hash code for the <see cref="CompoundType"/> based on its item's span.
+        /// It is used for efficient storage and retrieval in hash-based collections.
+        ///
+        /// Use this method when you need a hash code for a <see cref="CompoundType"/>.
         /// </summary>
-        /// <exception cref="NotSupportedException">This method always throws the exception.</exception>
+        /// <returns>The hash code for the <see cref="CompoundType"/>.</returns>
         public override int GetHashCode()
         {
-            throw new NotSupportedException();
+            var h = new HashCode();
+            h.Add(Count);
+            h.Add(Type);
+            foreach (var item in SubItems)
+            {
+                // This isn't prefect and leaves somethings unsolved.
+                if (item is CompoundType cItem)
+                {
+                    h.Add(cItem.Count);
+                    h.Add(cItem.Type);
+                }
+                else
+                {
+                    h.Add(item.GetHashCode());
+                }
+            }
+            return h.ToHashCode();
         }
 
         public override string ToString()

tests/Neo.VM.Tests/UT_StackItem.cs

@@ -19,6 +19,21 @@ namespace Neo.Test
     [TestClass]
     public class UT_StackItem
     {
+        [TestMethod]
+        public void TestCircularReference()
+        {
+            var itemA = new Struct { true, false };
+            var itemB = new Struct { true, false };
+            var itemC = new Struct { false, false };
+
+            itemA[1] = itemA;
+            itemB[1] = itemB;
+            itemC[1] = itemC;
+
+            Assert.AreEqual(itemA.GetHashCode(), itemB.GetHashCode());
+            Assert.AreNotEqual(itemA.GetHashCode(), itemC.GetHashCode());
+        }
+
         [TestMethod]
         public void TestHashCode()
         {
@@ -62,17 +77,35 @@ public void TestHashCode()
 
             Assert.IsTrue(itemA.GetHashCode() == itemB.GetHashCode());
 
-            itemA = new VM.Types.Array();
+            itemA = new Array { true, false, 0 };
+            itemB = new Array { true, false, 0 };
+            itemC = new Array { true, false, 1 };
+
+            Assert.IsTrue(itemA.GetHashCode() == itemB.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() != itemC.GetHashCode());
+
+            itemA = new Struct { true, false, 0 };
+            itemB = new Struct { true, false, 0 };
+            itemC = new Struct { true, false, 1 };
 
-            Assert.ThrowsException<System.NotSupportedException>(() => itemA.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() == itemB.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() != itemC.GetHashCode());
 
-            itemA = new Struct();
+            itemA = new Map { [true] = false, [0] = 1 };
+            itemB = new Map { [true] = false, [0] = 1 };
+            itemC = new Map { [true] = false, [0] = 2 };
 
-            Assert.ThrowsException<System.NotSupportedException>(() => itemA.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() == itemB.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() != itemC.GetHashCode());
 
-            itemA = new Map();
+            // Test CompoundType GetHashCode for subitems
+            var junk = new Array { true, false, 0 };
+            itemA = new Map { [true] = junk, [0] = junk };
+            itemB = new Map { [true] = junk, [0] = junk };
+            itemC = new Map { [true] = junk, [0] = 2 };
 
-            Assert.ThrowsException<System.NotSupportedException>(() => itemA.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() == itemB.GetHashCode());
+            Assert.IsTrue(itemA.GetHashCode() != itemC.GetHashCode());
 
             itemA = new InteropInterface(123);
             itemB = new InteropInterface(123);