diff --git a/lib/mixins/dir-mixin.js b/lib/mixins/dir-mixin.js
index 0b2326fdc4..1957bb489c 100644
--- a/lib/mixins/dir-mixin.js
+++ b/lib/mixins/dir-mixin.js
@@ -83,6 +83,9 @@ function takeRecords() {
  * @mixinFunction
  * @polymer
  * @appliesMixin PropertyAccessors
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const DirMixin = dedupingMixin((base) => {
 
diff --git a/lib/mixins/disable-upgrade-mixin.js b/lib/mixins/disable-upgrade-mixin.js
index 7cb9e894fa..8b2022a6eb 100644
--- a/lib/mixins/disable-upgrade-mixin.js
+++ b/lib/mixins/disable-upgrade-mixin.js
@@ -38,6 +38,9 @@ const DISABLED_ATTR = 'disable-upgrade';
  * @mixinFunction
  * @polymer
  * @appliesMixin ElementMixin
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const DisableUpgradeMixin = dedupingMixin((base) => {
   /**
diff --git a/lib/mixins/element-mixin.js b/lib/mixins/element-mixin.js
index ab10624cc2..522914b33b 100644
--- a/lib/mixins/element-mixin.js
+++ b/lib/mixins/element-mixin.js
@@ -95,6 +95,9 @@ const builtCSS = window.ShadyCSS && window.ShadyCSS['cssBuild'];
  *   import strategies.
  * @summary Element class mixin that provides the core API for Polymer's
  * meta-programming features.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const ElementMixin = dedupingMixin(base => {
   /**
diff --git a/lib/mixins/gesture-event-listeners.js b/lib/mixins/gesture-event-listeners.js
index 04dc14fd89..71a4577ff7 100644
--- a/lib/mixins/gesture-event-listeners.js
+++ b/lib/mixins/gesture-event-listeners.js
@@ -24,65 +24,48 @@ import { addListener, removeListener } from '../utils/gestures.js';
  * @mixinFunction
  * @polymer
  * @summary Element class mixin that provides API for adding Polymer's
- *   cross-platform
- * gesture events to nodes
+ *   cross-platform gesture events to nodes
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
-const GestureEventListeners = dedupingMixin(
+export const GestureEventListeners = dedupingMixin((superClass) => {
+  /**
+   * @polymer
+   * @mixinClass
+   * @implements {Polymer_GestureEventListeners}
+   */
+  class GestureEventListeners extends superClass {
     /**
-     * @template T
-     * @param {function(new:T)} superClass Class to apply mixin to.
-     * @return {function(new:T)} superClass with mixin applied.
+     * Add the event listener to the node if it is a gestures event.
+     *
+     * @param {!EventTarget} node Node to add event listener to
+     * @param {string} eventName Name of event
+     * @param {function(!Event):void} handler Listener function to add
+     * @return {void}
+     * @override
      */
-    (superClass) => {
-      /**
-       * @polymer
-       * @mixinClass
-       * @implements {Polymer_GestureEventListeners}
-       */
-      class GestureEventListeners extends superClass {
-        /**
-         * Add the event listener to the node if it is a gestures event.
-         *
-         * @param {!EventTarget} node Node to add event listener to
-         * @param {string} eventName Name of event
-         * @param {function(!Event):void} handler Listener function to add
-         * @return {void}
-         * @override
-         */
-        _addEventListenerToNode(node, eventName, handler) {
-          if (!addListener(node, eventName, handler)) {
-            super._addEventListenerToNode(node, eventName, handler);
-          }
-        }
-
-        /**
-         * Remove the event listener to the node if it is a gestures event.
-         *
-         * @param {!EventTarget} node Node to remove event listener from
-         * @param {string} eventName Name of event
-         * @param {function(!Event):void} handler Listener function to remove
-         * @return {void}
-         * @override
-         */
-        _removeEventListenerFromNode(node, eventName, handler) {
-          if (!removeListener(node, eventName, handler)) {
-            super._removeEventListenerFromNode(node, eventName, handler);
-          }
-        }
+    _addEventListenerToNode(node, eventName, handler) {
+      if (!addListener(node, eventName, handler)) {
+        super._addEventListenerToNode(node, eventName, handler);
       }
+    }
 
-      return GestureEventListeners;
-    });
-
-// Somehow GestureEventListeners is incorrectly typed as *. For now add this
-// cast.
-/**
- * @template T
- * @param {function(new:T)} superClass Class to apply mixin to.
- * @return {function(new:T)} superClass with mixin applied.
- */
-const _GestureEventListeners = function(superClass) {
-  return GestureEventListeners(superClass);
-};
+    /**
+     * Remove the event listener to the node if it is a gestures event.
+     *
+     * @param {!EventTarget} node Node to remove event listener from
+     * @param {string} eventName Name of event
+     * @param {function(!Event):void} handler Listener function to remove
+     * @return {void}
+     * @override
+     */
+    _removeEventListenerFromNode(node, eventName, handler) {
+      if (!removeListener(node, eventName, handler)) {
+        super._removeEventListenerFromNode(node, eventName, handler);
+      }
+    }
+  }
 
-export {_GestureEventListeners as GestureEventListeners};
+  return GestureEventListeners;
+});
diff --git a/lib/mixins/mutable-data.js b/lib/mixins/mutable-data.js
index d38b5119b9..12072ac47a 100644
--- a/lib/mixins/mutable-data.js
+++ b/lib/mixins/mutable-data.js
@@ -67,6 +67,9 @@ function mutablePropertyChange(inst, property, value, old, mutableData) {
  * @polymer
  * @summary Element class mixin to skip strict dirty-checking for objects
  *   and arrays
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const MutableData = dedupingMixin(superClass => {
 
diff --git a/lib/mixins/properties-changed.js b/lib/mixins/properties-changed.js
index 363138b1ac..ff49a5746b 100644
--- a/lib/mixins/properties-changed.js
+++ b/lib/mixins/properties-changed.js
@@ -33,6 +33,9 @@ const microtask = microTask;
  * @polymer
  * @summary Element class mixin for reacting to property changes from
  *   generated property accessors.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const PropertiesChanged = dedupingMixin(
     /**
diff --git a/lib/mixins/properties-mixin.js b/lib/mixins/properties-mixin.js
index d450cfd299..06fe449d38 100644
--- a/lib/mixins/properties-mixin.js
+++ b/lib/mixins/properties-mixin.js
@@ -47,6 +47,9 @@ function normalizeProperties(props) {
  * @appliesMixin PropertiesChanged
  * @summary Mixin that provides a minimal starting point for using
  * the PropertiesChanged mixin by providing a declarative `properties` object.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const PropertiesMixin = dedupingMixin(superClass => {
 
diff --git a/lib/mixins/property-accessors.js b/lib/mixins/property-accessors.js
index 16d039ef82..2590165c03 100644
--- a/lib/mixins/property-accessors.js
+++ b/lib/mixins/property-accessors.js
@@ -91,6 +91,9 @@ function saveAccessorValue(model, property) {
  * @appliesMixin PropertiesChanged
  * @summary Element class mixin for reacting to property changes from
  *   generated property accessors.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const PropertyAccessors = dedupingMixin(superClass => {
 
diff --git a/lib/mixins/property-effects.js b/lib/mixins/property-effects.js
index 3affb2661b..af8968606a 100644
--- a/lib/mixins/property-effects.js
+++ b/lib/mixins/property-effects.js
@@ -1079,6 +1079,9 @@ function upper(name) {
  * @appliesMixin PropertyAccessors
  * @summary Element class mixin that provides meta-programming for Polymer's
  * template binding and data observation system.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const PropertyEffects = dedupingMixin(superClass => {
 
diff --git a/lib/mixins/strict-binding-parser.js b/lib/mixins/strict-binding-parser.js
index 924c69c70f..6027fee112 100644
--- a/lib/mixins/strict-binding-parser.js
+++ b/lib/mixins/strict-binding-parser.js
@@ -115,6 +115,9 @@ function storeMethodNumber(bindingData, text, i) {
  * @appliesMixin PropertyEffects
  * @polymer
  * @summary Mixin that parses binding expressions and generates corresponding metadata.
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 const StrictBindingParser = dedupingMixin((base) => {
 
diff --git a/lib/mixins/template-stamp.js b/lib/mixins/template-stamp.js
index 99313a1165..e7a576ec2a 100644
--- a/lib/mixins/template-stamp.js
+++ b/lib/mixins/template-stamp.js
@@ -104,6 +104,9 @@ function createNodeEventHandler(context, eventName, methodName) {
  * @mixinFunction
  * @polymer
  * @summary Element class mixin that provides basic template parsing and stamping
+ * @template T
+ * @param {function(new:T)} superClass Class to apply mixin to.
+ * @return {function(new:T)} superClass with mixin applied.
  */
 export const TemplateStamp = dedupingMixin(
     /**