[Compiler UT] Ut readonly property (#984)

* add property method test

* format

* Update tests/Neo.Compiler.CSharp.TestContracts/Contract_PropertyMethod.cs

* update UT

* fix readonly set

* update comments

* add document reference

* fix comments

* remvoe static set. Its not supported by C#

* format

* remove constructor check as syntax analyzer will handle it.

---------

Co-authored-by: Shargon <shargon@gmail.com>

src/Neo.Compiler.CSharp/MethodConvert/Expression/AssignmentExpression.SimpleAssignment.cs

@@ -15,6 +15,7 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Neo.VM;
 using System;
+using System.Linq;
 using System.Runtime.InteropServices;
 
 namespace Neo.Compiler;
@@ -139,8 +140,34 @@ private void ConvertIdentifierNameAssignment(SemanticModel model, IdentifierName
                 AccessSlot(OpCode.STARG, _parameters[parameter]);
                 break;
             case IPropertySymbol property:
-                if (!property.IsStatic) AddInstruction(OpCode.LDARG0);
-                Call(model, property.SetMethod!, CallingConvention.Cdecl);
+                // Check if the property is within a constructor and is readonly
+                // C# document here https://learn.microsoft.com/en-us/dotnet/csharp/properties
+                // example of this syntax:
+                // public class Person
+                // {
+                //     public Person(string firstName) => FirstName = firstName;
+                //     // Readonly property
+                //     public string FirstName { get; }
+                // }
+                if (property.SetMethod == null)
+                {
+                    IFieldSymbol[] fields = property.ContainingType.GetAllMembers().OfType<IFieldSymbol>().ToArray();
+                    fields = fields.Where(p => !p.IsStatic).ToArray();
+                    int backingFieldIndex = Array.FindIndex(fields, p => SymbolEqualityComparer.Default.Equals(p.AssociatedSymbol, property));
+                    AccessSlot(OpCode.LDARG, 0);
+                    Push(backingFieldIndex);
+                    AddInstruction(OpCode.ROT);
+                    AddInstruction(OpCode.SETITEM);
+                }
+                else if (property.SetMethod != null)
+                {
+                    if (!property.IsStatic) AddInstruction(OpCode.LDARG0);
+                    Call(model, property.SetMethod, CallingConvention.Cdecl);
+                }
+                else
+                {
+                    throw new CompilationException(left, DiagnosticId.SyntaxNotSupported, $"Property is readonly and not within a constructor: {property.Name}");
+                }
                 break;
             default:
                 throw new CompilationException(left, DiagnosticId.SyntaxNotSupported, $"Unsupported symbol: {symbol}");

tests/Neo.Compiler.CSharp.TestContracts/Contract_PropertyMethod.cs

@@ -0,0 +1,27 @@
+namespace Neo.Compiler.CSharp.UnitTests.TestClasses;
+
+public class Contract_PropertyMethod : SmartContract.Framework.SmartContract
+{
+    public static (string, int) testProperty()
+    {
+        var p = new Person("NEO3", 10);
+        return (p.Name, p.Age);
+    }
+
+    public static void testProperty2()
+    {
+        var p = new Person("NEO3", 10);
+    }
+
+    public class Person
+    {
+        public string Name { get; set; }
+        public int Age { get; }
+
+        public Person(string name, int age)
+        {
+            Name = name;
+            Age = age;
+        }
+    }
+}

tests/Neo.Compiler.CSharp.UnitTests/UnitTest_Property_Method.cs

@@ -0,0 +1,39 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.SmartContract.TestEngine;
+using Neo.VM;
+using Neo.VM.Types;
+
+namespace Neo.Compiler.CSharp.UnitTests
+{
+    [TestClass]
+    public class UnitTest_Property_Method
+    {
+        private TestEngine testEngine;
+
+        [TestInitialize]
+        public void Init()
+        {
+            testEngine = new TestEngine();
+            testEngine.AddNoOptimizeEntryScript(Utils.Extensions.TestContractRoot + "Contract_PropertyMethod.cs");
+        }
+
+        [TestMethod]
+        public void TestPropertyMethod()
+        {
+            testEngine.Reset();
+            var res = testEngine.ExecuteTestCaseStandard("testProperty");
+            Assert.AreEqual(testEngine.State, VMState.HALT);
+            var arr = (Array)res.Pop();
+            Assert.AreEqual(arr[0].GetString(), "NEO3");
+            Assert.AreEqual(arr[1].GetInteger(), 10);
+        }
+
+        [TestMethod]
+        public void TestPropertyMethod2()
+        {
+            testEngine.Reset();
+            var res = testEngine.ExecuteTestCaseStandard("testProperty2");
+            Assert.AreEqual(testEngine.State, VMState.HALT);
+        }
+    }
+}