move super reference into closure

lib/6to5/transformation/transformers/es6-classes.js

@@ -58,15 +58,23 @@ Class.prototype.run = function () {
     t.variableDeclarator(className, constructor)
   ]));
 
+  var closureArgs = [];
+  var closureParams = [];
+
   //
 
   if (superName) {
-    // so we're only evaluating it once
-    var superRef = this.scope.generateUidBasedOnNode(superName, this.file);
-    body.unshift(t.variableDeclaration("var", [
-      t.variableDeclarator(superRef, superName)
-    ]));
-    superName = superRef;
+    closureArgs.push(superName);
+
+    if (!t.isIdentifier(superName)) {
+      var superRef = this.scope.generateUidBasedOnNode(superName, this.file);
+      body.unshift(t.variableDeclaration("var", [
+        t.variableDeclarator(superRef, superName)
+      ]));
+      superName = superRef;
+    }
+
+    closureParams.push(superName);
 
     this.superName = superName;
     body.push(t.expressionStatement(t.callExpression(file.addHelper("inherits"), [className, superName])));
@@ -84,8 +92,8 @@ Class.prototype.run = function () {
   } else {
     body.push(t.returnStatement(className));
     init = t.callExpression(
-      t.functionExpression(null, [], t.blockStatement(body)),
-      []
+      t.functionExpression(null, closureParams, t.blockStatement(body)),
+      closureArgs
     );
   }
 
@@ -212,25 +220,12 @@ Class.prototype.superProperty = function (property, isStatic, isComputed) {
     this.file.addHelper("get"),
     [
       t.callExpression(
-        t.memberExpression(
-          t.identifier("Object"),
-          t.identifier("getPrototypeOf"),
-          false
-        ),
+        t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
         [
-          isStatic ?
-            this.className :
-            t.memberExpression(
-              this.className,
-              t.identifier("prototype"),
-              false
-            )
+          isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
         ]
       ),
-      isComputed ?
-        property :
-        t.literal(property.name),
-      t.thisExpression()
+      isComputed ? property : t.literal(property.name), t.thisExpression()
     ]
   );
 };