新增赋值操作

ExpressionElements/Assignment.cs

@@ -0,0 +1,68 @@
+using System;
+using Flee.ExpressionElements.Base;
+using Flee.ExpressionElements.MemberElements;
+using Flee.InternalTypes;
+using Flee.PublicTypes;
+
+namespace Flee.ExpressionElements
+{
+    internal class AssignmentElement : ExpressionElement
+    {
+        private readonly string _variableName;
+        private readonly ExpressionElement _valueExpression;
+        private readonly ExpressionContext _context;
+
+        public AssignmentElement(string variableName, ExpressionElement valueExpression, ExpressionContext context)
+        {
+            _variableName = variableName;
+            _valueExpression = valueExpression;
+            _context = context;
+            
+            // 检查变量是否存在
+            if (!_context.Variables.ContainsKey(_variableName))
+            {
+                this.ThrowCompileException("UndefinedVariable", CompileExceptionReason.UndefinedName, _variableName);
+            }
+        }
+
+        public override void Emit(FleeILGenerator ilg, IServiceProvider services)
+        {
+            // 首先计算右侧表达式的值
+            _valueExpression.Emit(ilg, services);
+            
+            // 获取一个临时本地变量来存储值
+            var valueType = _valueExpression.ResultType;
+            int tempIndex = ilg.GetTempLocalIndex(valueType);
+            
+            // 存储值到临时变量
+            Utility.EmitStoreLocal(ilg, tempIndex);
+            
+            // 加载变量集合 (arg 2)
+            ilg.Emit(System.Reflection.Emit.OpCodes.Ldarg_2); // 加载 VariableCollection
+            
+            // 加载变量名
+            ilg.Emit(System.Reflection.Emit.OpCodes.Ldstr, _variableName);
+            
+            // 加载要设置的值
+            Utility.EmitLoadLocal(ilg, tempIndex);
+            
+            // 如果值类型是值类型，需要装箱
+            if (valueType.IsValueType)
+            {
+                ilg.Emit(System.Reflection.Emit.OpCodes.Box, valueType);
+            }
+            
+            // 调用 Variables[string] 的 setter
+            var indexerSetter = typeof(VariableCollection).GetProperty("Item", new Type[] { typeof(string) }).GetSetMethod();
+            ilg.Emit(System.Reflection.Emit.OpCodes.Callvirt, indexerSetter);
+            
+            // 加载返回值到栈上
+            Utility.EmitLoadLocal(ilg, tempIndex);
+        }
+
+        public override Type ResultType
+        {
+            get { return _valueExpression.ResultType; }
+        }
+    }
+}