From 123186003c3d4d6a6ec734dd37e699b043e8b59a Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Tue, 13 Jan 2015 01:00:35 +1100
Subject: [PATCH] add support for super instead of closures - fixes #425

---
 .../transformers/es6-classes.js               | 105 +++++++++++-------
 1 file changed, 64 insertions(+), 41 deletions(-)

diff --git a/lib/6to5/transformation/transformers/es6-classes.js b/lib/6to5/transformation/transformers/es6-classes.js
index 55d09c3c60..15f8b7addc 100644
--- a/lib/6to5/transformation/transformers/es6-classes.js
+++ b/lib/6to5/transformation/transformers/es6-classes.js
@@ -62,8 +62,8 @@ Class.prototype.run = function () {
   }
   this.constructor = constructor;
 
-  var closureArgs = [];
   var closureParams = [];
+  var closureArgs = [];
 
   //
 
@@ -229,54 +229,77 @@ Class.prototype.replaceInstanceSuperReferences = function (methodNode) {
   var method = methodNode.value;
   var self   = this;
 
-  traverse(method, {
-    enter: function (node, parent) {
-      var property;
-      var computed;
-      var args;
+  var topLevelThisReference;
 
-      if (t.isIdentifier(node, { name: "super" })) {
-        if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
-          throw self.file.errorWithNode(node, "illegal use of bare super");
+  traverse2(method, true);
+
+  if (topLevelThisReference) {
+    method.body.body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(topLevelThisReference, t.thisExpression())
+    ]));
+  }
+
+  function traverse2(node, topLevel) {
+    traverse(node, {
+      enter: function (node, parent) {
+        if (t.isFunction(node) && !t.isArrowFunctionExpression(node)) {
+          traverse2(node, false);
+          return this.skip();
         }
-      } else if (t.isCallExpression(node)) {
-        var callee = node.callee;
-        if (t.isIdentifier(callee, { name: "super" })) {
-          // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
-          property = methodNode.key;
-          computed = methodNode.computed;
-          args = node.arguments;
-        } else {
-          if (!t.isMemberExpression(callee)) return;
-          if (callee.object.name !== "super") return;
 
-          // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
-          property = callee.property;
-          computed = callee.computed;
-          args = node.arguments;
+        var property;
+        var computed;
+        var args;
+
+        if (t.isIdentifier(node, { name: "super" })) {
+          if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
+            throw self.file.errorWithNode(node, "illegal use of bare super");
+          }
+        } else if (t.isCallExpression(node)) {
+          var callee = node.callee;
+          if (t.isIdentifier(callee, { name: "super" })) {
+            // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
+            property = methodNode.key;
+            computed = methodNode.computed;
+            args = node.arguments;
+          } else {
+            if (!t.isMemberExpression(callee)) return;
+            if (callee.object.name !== "super") return;
+
+            // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
+            property = callee.property;
+            computed = callee.computed;
+            args = node.arguments;
+          }
+        } else if (t.isMemberExpression(node)) {
+          if (!t.isIdentifier(node.object, { name: "super" })) return;
+
+          // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
+          property = node.property;
+          computed = node.computed;
         }
-      } else if (t.isMemberExpression(node)) {
-        if (!t.isIdentifier(node.object, { name: "super" })) return;
 
-        // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
-        property = node.property;
-        computed = node.computed;
-      }
+        if (property) {
+          var thisReference;
+          if (topLevel) {
+            thisReference = t.thisExpression();
+          } else {
+            topLevelThisReference = thisReference = topLevelThisReference || self.file.generateUidIdentifier("this");
+          }
 
-      if (property) {
-        var thisExpression = t.thisExpression();
-        var superProperty = self.superProperty(property, methodNode.static, computed, thisExpression);
-        if (args) {
-          return t.callExpression(
-            t.memberExpression(superProperty, t.identifier("call"), false),
-            [thisExpression].concat(args)
-          );
-        } else {
-          return superProperty;
+          var superProperty = self.superProperty(property, methodNode.static, computed, thisReference);
+          if (args) {
+            return t.callExpression(
+              t.memberExpression(superProperty, t.identifier("call"), false),
+              [thisReference].concat(args)
+            );
+          } else {
+            return superProperty;
+          }
         }
       }
-    }
-  });
+    });
+  }
 };
 
 /**