Support use of super inside instance setter.

lib/6to5/file.js

@@ -39,7 +39,8 @@ File.helpers = [
   "interop-require-wildcard",
   "typeof",
   "extends",
-  "get"
+  "get",
+  "set"
 ];
 
 File.excludeHelpersFromRuntime = [

lib/6to5/transformation/helpers/replace-supers.js

@@ -24,6 +24,36 @@ function ReplaceSupers(methodNode, className, superName, isLoose, file) {
   this.file                  = file;
 }
 
+/**
+ * Sets a super class value of the named property.
+ *
+ * @example
+ *
+ *   _set(Object.getPrototypeOf(CLASS.prototype), "METHOD", "VALUE", this)
+ *
+ * @param {Node} property
+ * @param {boolean} isStatic
+ * @param {boolean} isComputed
+ *
+ * @returns {Node}
+ */
+ReplaceSupers.prototype.setSuperProperty = function (property, value, isStatic, isComputed, thisExpression) {
+  return t.callExpression(
+    this.file.addHelper("set"),
+    [
+      t.callExpression(
+        t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
+        [
+          isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+        ]
+      ),
+      isComputed ? property : t.literal(property.name),
+      t.identifier(value.name),
+      thisExpression
+    ]
+  );
+};
+
 /**
  * Gets a node representing the super class value of the named property.
  *
@@ -194,6 +224,7 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
   var property;
   var computed;
   var args;
+  var thisReference;
 
   if (t.isIdentifier(node, { name: "super" })) {
     if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
@@ -221,11 +252,18 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
     // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
     property = node.property;
     computed = node.computed;
+  } else if (t.isAssignmentExpression(node)) {
+    if (!t.isIdentifier(node.left.object, { name: "super" })) return;
+    if (methodNode.kind !== 'set') return;
+
+    thisReference = getThisReference();
+    // super.name = "val"; -> _set(Object.getPrototypeOf(ClassName.prototype), "name", this);
+    return this.setSuperProperty(node.left.property, node.right, methodNode.static, node.left.computed, thisReference);
   }
 
   if (!property) return;
 
-  var thisReference = getThisReference();
+  thisReference = getThisReference();
   var superProperty = this.superProperty(property, methodNode.static, computed, thisReference);
   if (args) {
     if (args.length === 1 && t.isSpreadElement(args[0])) {

lib/6to5/transformation/templates/set.js

@@ -0,0 +1,24 @@
+(function set(object, property, value, receiver) {
+  var desc = Object.getOwnPropertyDescriptor(object, property);
+
+  if (desc === undefined) {
+    var parent = Object.getPrototypeOf(object);
+
+    if (parent === null) {
+      return;
+    } else {
+      return set(parent, property, value, receiver);
+    }
+  } else if ("value" in desc && desc.writable) {
+    desc.value = value;
+    return;
+  } else {
+    var setter = desc.set;
+
+    if (setter === undefined) {
+      return;
+    }
+
+    return setter.call(receiver, value);
+  }
+});