解离出Runner

DoRunner/EnterNamespaceRunner.cs

@@ -0,0 +1,23 @@
+using Convention.RScript.Parser;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Convention.RScript.Runner
+{
+    public class EnterNamespaceRunner : IRSentenceRunner
+    {
+        [return: MaybeNull]
+        public object Run(ExpressionParser parser, RScriptSentence sentence, RScriptContext context)
+        {
+            // 准备记录当前命名空间中定义的变量, 清空上层命名空间的变量
+            context.CurrentLocalSpaceVariableNames.Push(new());
+            // 更新变量值
+            foreach (var (varName, varValue) in parser.context.Variables)
+            {
+                context.Variables.SetValue(varName, varValue);
+            }
+            // 压栈
+            context.RuntimePointerStack.Push(context.CurrentRuntimePointer);
+            return null;
+        }
+    }
+}