move shadow function visitors to entrance instead of exit

src/babel/transformation/transformers/internal/shadow-functions.js

@@ -89,21 +89,17 @@ export var metadata = {
   group: "builtin-trailing"
 };
 
-export var Program = {
-  exit(node, parent, scope) {
-    aliasFunction(function () {
-      return node.body;
-    }, this, scope);
-  }
-};
+export function Program(node, parent, scope) {
+  aliasFunction(function () {
+    return node.body;
+  }, this, scope);
+}
 
-export var FunctionDeclaration = {
-  exit(node, parent, scope) {
-    aliasFunction(function () {
-      t.ensureBlock(node);
-      return node.body.body;
-    }, this, scope);
-  }
-};
+export function FunctionDeclaration(node, parent, scope) {
+  aliasFunction(function () {
+    t.ensureBlock(node);
+    return node.body.body;
+  }, this, scope);
+}
 
 export { FunctionDeclaration as FunctionExpression };

test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js

@@ -11,17 +11,17 @@ function one() {
 one(1, 2);
 
 function two() {
-  var _arguments3 = arguments;
+  var _arguments2 = arguments;
 
   var inner = function inner() {
-    return _arguments3;
+    return _arguments2;
   };
 
   var another = function another() {
-    var _arguments2 = arguments;
+    var _arguments3 = arguments;
 
     var inner2 = function inner2() {
-      return _arguments2;
+      return _arguments3;
     };
   };