解离出Runner

DoRunner/ExitNamespaceRunner.cs

@@ -0,0 +1,28 @@
+using Convention.RScript.Parser;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Convention.RScript.Runner
+{
+    public class ExitNamespaceRunner : IRSentenceRunner
+    {
+        [return: MaybeNull]
+        public object Run(ExpressionParser parser, RScriptSentence sentence, RScriptContext context)
+        {
+            // 移除当前命名空间的变量
+            foreach (var local in context.CurrentLocalSpaceVariableNames.Peek())
+            {
+                context.Variables.Remove(local);
+                parser.context.Variables.Remove(local);
+            }
+            // 还原上层命名空间的变量
+            foreach (var local in context.CurrentLocalSpaceVariableNames.Peek())
+            {
+                parser.context.Variables[local] = context.Variables[local].data;
+            }
+            context.CurrentLocalSpaceVariableNames.Pop();
+            // 弹栈
+            context.RuntimePointerStack.Pop();
+            return null;
+        }
+    }
+}