diff --git a/lib/legacy/class.js b/lib/legacy/class.js
index 73f59dd1ac..bb4326e370 100644
--- a/lib/legacy/class.js
+++ b/lib/legacy/class.js
@@ -180,7 +180,7 @@ function flattenBehaviors(behaviors, list, exclude) {
 /**
  * @param {!PolymerInit} info Polymer info object
  * @param {function(new:HTMLElement)} Base base class to extend with info object
- * @param {Object} behaviors behaviors to copy into the element
+ * @param {Object=} behaviors behaviors to copy into the element
  * @return {function(new:HTMLElement)} Generated class
  * @suppress {checkTypes}
  * @private
@@ -197,7 +197,7 @@ function GenerateClassFromInfo(info, Base, behaviors) {
     // explicitly not calling super._finalizeClass
     static _finalizeClass() {
       // if calling via a subclass that hasn't been generated, pass through to super
-      if (!this.hasOwnProperty(window.JSCompiler_renameProperty('generatedFrom', this))) {
+      if (!this.hasOwnProperty(JSCompiler_renameProperty('generatedFrom', this))) {
         super._finalizeClass();
       } else {
         // interleave properties and observers per behavior and `info`
diff --git a/lib/legacy/legacy-data-mixin.js b/lib/legacy/legacy-data-mixin.js
index 0788e4a3c6..b2a255386d 100644
--- a/lib/legacy/legacy-data-mixin.js
+++ b/lib/legacy/legacy-data-mixin.js
@@ -151,12 +151,31 @@ Polymer.Class = (info, mixin) => Class(info,
 
 // Apply LegacyDataMixin to Templatizer instances as well, and defer
 // runtime switch to the root's host (_methodHost)
-templatize.mixin = 
-  dedupingMixin(superClass => class extends LegacyDataMixin(superClass) {
-    get _legacyUndefinedCheck() {
-      return this._methodHost && this._methodHost._legacyUndefinedCheck;
+/**
+ * @mixinFunction
+ * @polymer
+ */
+const TemplatizeMixin =
+  dedupingMixin(superClass => {
+    /**
+     * @constructor
+     * @extends {HTMLElement}
+     */
+    const legacyBase = LegacyDataMixin(superClass);
+    /**
+     * @private
+     */
+    class TemplateLegacy extends legacyBase {
+      get _legacyUndefinedCheck() {
+        return this._methodHost && this._methodHost._legacyUndefinedCheck;
+      }
     }
+    /** @type {!Polymer_PropertyEffects} */
+    TemplateLegacy.prototype._methodHost;
+    return TemplateLegacy;
   });
 
+templatize.mixin = TemplatizeMixin;
+
 console.info('LegacyDataMixin will be applied to all legacy elements.\n' +
               'Set `_legacyUndefinedCheck: true` on element class to enable.');
diff --git a/lib/legacy/legacy-element-mixin.js b/lib/legacy/legacy-element-mixin.js
index a32ada9d21..2ea2866a2c 100644
--- a/lib/legacy/legacy-element-mixin.js
+++ b/lib/legacy/legacy-element-mixin.js
@@ -530,7 +530,7 @@ export const LegacyElementMixin = dedupingMixin((base) => {
      */
     distributeContent() {
       const thisEl = /** @type {Element} */ (this);
-      const domApi = /** @type {DomApi} */(dom(thisEl));
+      const domApi = /** @type {PolymerDomApi} */(dom(thisEl));
       if (window.ShadyDOM && domApi.shadowRoot) {
         ShadyDOM.flush();
       }
@@ -879,9 +879,9 @@ export const LegacyElementMixin = dedupingMixin((base) => {
      * @override
      */
     toggleAttribute(name, bool) {
-      let node = /** @type {Element} */ this;
+      let node = /** @type {Element} */(this);
       if (arguments.length === 3) {
-        node = /** @type {Element} */ arguments[2];
+        node = /** @type {Element} */(arguments[2]);
       }
       if (arguments.length == 1) {
         bool = !node.hasAttribute(name);
diff --git a/lib/legacy/polymer.dom.js b/lib/legacy/polymer.dom.js
index c7f2b04693..442d428147 100644
--- a/lib/legacy/polymer.dom.js
+++ b/lib/legacy/polymer.dom.js
@@ -42,7 +42,7 @@ export const matchesSelector = function(node, selector) {
  * @implements {PolymerDomApi}
  * @unrestricted
  */
-let DomApi = class {
+class DomApiNative {
 
   /**
    * @param {Node} node Node for which to create a Polymer.dom helper object.
@@ -197,20 +197,20 @@ let DomApi = class {
    * For shadow roots, returns the currently focused element within this
    * shadow root.
    *
-   * @return {Node|undefined} Currently focused element
+   * return {Node|undefined} Currently focused element
    * @override
    */
   get activeElement() {
     let node = this.node;
     return node._activeElement !== undefined ? node._activeElement : node.activeElement;
   }
-};
+}
 
 function forwardMethods(proto, methods) {
   for (let i=0; i < methods.length; i++) {
     let method = methods[i];
     /* eslint-disable valid-jsdoc */
-    proto[method] = /** @this {DomApi} */ function() {
+    proto[method] = /** @this {DomApiNative} */ function() {
       return this.node[method].apply(this.node, arguments);
     };
     /* eslint-enable */
@@ -222,7 +222,7 @@ function forwardReadOnlyProperties(proto, properties) {
     let name = properties[i];
     Object.defineProperty(proto, name, {
       get: function() {
-        const domApi = /** @type {DomApi} */(this);
+        const domApi = /** @type {DomApiNative} */(this);
         return domApi.node[name];
       },
       configurable: true
@@ -235,14 +235,14 @@ function forwardProperties(proto, properties) {
     let name = properties[i];
     Object.defineProperty(proto, name, {
       /**
-       * @this {DomApi}
+       * @this {DomApiNative}
        * @return {*} .
        */
       get: function() {
         return this.node[name];
       },
       /**
-       * @this {DomApi}
+       * @this {DomApiNative}
        * @param {*} value .
        */
       set: function(value) {
@@ -295,90 +295,90 @@ export class EventApi {
  * @param {boolean=} deep
  * @return {!Node}
  */
-DomApi.prototype.cloneNode;
+DomApiNative.prototype.cloneNode;
 /**
  * @function
  * @param {!Node} node
  * @return {!Node}
  */
-DomApi.prototype.appendChild;
+DomApiNative.prototype.appendChild;
 /**
  * @function
  * @param {!Node} newChild
  * @param {Node} refChild
  * @return {!Node}
  */
-DomApi.prototype.insertBefore;
+DomApiNative.prototype.insertBefore;
 /**
  * @function
  * @param {!Node} node
  * @return {!Node}
  */
-DomApi.prototype.removeChild;
+DomApiNative.prototype.removeChild;
 /**
  * @function
  * @param {!Node} oldChild
  * @param {!Node} newChild
  * @return {!Node}
  */
-DomApi.prototype.replaceChild;
+DomApiNative.prototype.replaceChild;
 /**
  * @function
  * @param {string} name
  * @param {string} value
  * @return {void}
  */
-DomApi.prototype.setAttribute;
+DomApiNative.prototype.setAttribute;
 /**
  * @function
  * @param {string} name
  * @return {void}
  */
-DomApi.prototype.removeAttribute;
+DomApiNative.prototype.removeAttribute;
 /**
  * @function
  * @param {string} selector
  * @return {?Element}
  */
-DomApi.prototype.querySelector;
+DomApiNative.prototype.querySelector;
 /**
  * @function
  * @param {string} selector
  * @return {!NodeList<!Element>}
  */
-DomApi.prototype.querySelectorAll;
+DomApiNative.prototype.querySelectorAll;
 
 /** @type {?Node} */
-DomApi.prototype.parentNode;
+DomApiNative.prototype.parentNode;
 /** @type {?Node} */
-DomApi.prototype.firstChild;
+DomApiNative.prototype.firstChild;
 /** @type {?Node} */
-DomApi.prototype.lastChild;
+DomApiNative.prototype.lastChild;
 /** @type {?Node} */
-DomApi.prototype.nextSibling;
+DomApiNative.prototype.nextSibling;
 /** @type {?Node} */
-DomApi.prototype.previousSibling;
+DomApiNative.prototype.previousSibling;
 /** @type {?HTMLElement} */
-DomApi.prototype.firstElementChild;
+DomApiNative.prototype.firstElementChild;
 /** @type {?HTMLElement} */
-DomApi.prototype.lastElementChild;
+DomApiNative.prototype.lastElementChild;
 /** @type {?HTMLElement} */
-DomApi.prototype.nextElementSibling;
+DomApiNative.prototype.nextElementSibling;
 /** @type {?HTMLElement} */
-DomApi.prototype.previousElementSibling;
+DomApiNative.prototype.previousElementSibling;
 /** @type {!Array<!Node>} */
-DomApi.prototype.childNodes;
+DomApiNative.prototype.childNodes;
 /** @type {!Array<!HTMLElement>} */
-DomApi.prototype.children;
+DomApiNative.prototype.children;
 /** @type {?DOMTokenList} */
-DomApi.prototype.classList;
+DomApiNative.prototype.classList;
 
 /** @type {string} */
-DomApi.prototype.textContent;
+DomApiNative.prototype.textContent;
 /** @type {string} */
-DomApi.prototype.innerHTML;
+DomApiNative.prototype.innerHTML;
 
-export {DomApi};
+let DomApiImpl = DomApiNative;
 
 if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noPatch'] && window['ShadyDOM']['Wrapper']) {
 
@@ -389,13 +389,13 @@ if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noP
   class Wrapper extends window['ShadyDOM']['Wrapper'] {}
 
   // copy bespoke API onto wrapper
-  Object.getOwnPropertyNames(DomApi.prototype).forEach((prop) => {
+  Object.getOwnPropertyNames(DomApiNative.prototype).forEach((prop) => {
     if (prop != 'activeElement') {
-      Wrapper.prototype[prop] = DomApi.prototype[prop];
+      Wrapper.prototype[prop] = DomApiNative.prototype[prop];
     }
   });
 
-  DomApi = Wrapper;
+  DomApiImpl = Wrapper;
 
   Object.defineProperties(EventApi.prototype, {
 
@@ -416,24 +416,26 @@ if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noP
 
 } else {
 
-  forwardMethods(DomApi.prototype, [
+  forwardMethods(DomApiNative.prototype, [
     'cloneNode', 'appendChild', 'insertBefore', 'removeChild',
     'replaceChild', 'setAttribute', 'removeAttribute',
     'querySelector', 'querySelectorAll'
   ]);
 
-  forwardReadOnlyProperties(DomApi.prototype, [
+  forwardReadOnlyProperties(DomApiNative.prototype, [
     'parentNode', 'firstChild', 'lastChild',
     'nextSibling', 'previousSibling', 'firstElementChild',
     'lastElementChild', 'nextElementSibling', 'previousElementSibling',
     'childNodes', 'children', 'classList'
   ]);
 
-  forwardProperties(DomApi.prototype, [
+  forwardProperties(DomApiNative.prototype, [
     'textContent', 'innerHTML'
   ]);
 }
 
+export const DomApi = DomApiImpl;
+
 /**
  * Legacy DOM and Event manipulation API wrapper factory used to abstract
  * differences between native Shadow DOM and "Shady DOM" when polyfilling on
@@ -445,12 +447,12 @@ if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noP
  *
  * @summary Legacy DOM and Event manipulation API wrapper factory used to
  * abstract differences between native Shadow DOM and "Shady DOM."
- * @param {(Node|Event|DomApi|EventApi)=} obj Node or event to operate on
- * @return {!DomApi|!EventApi} Wrapper providing either node API or event API
+ * @param {(Node|Event|DomApiNative|EventApi)=} obj Node or event to operate on
+ * @return {!DomApiNative|!EventApi} Wrapper providing either node API or event API
  */
 export const dom = function(obj) {
   obj = obj || document;
-  if (obj instanceof DomApi) {
+  if (obj instanceof DomApiImpl) {
     return /** @type {!DomApi} */(obj);
   }
   if (obj instanceof EventApi) {
@@ -461,7 +463,7 @@ export const dom = function(obj) {
     if (obj instanceof Event) {
       helper = new EventApi(obj);
     } else {
-      helper = new DomApi(/** @type {Node} */(obj));
+      helper = new DomApiImpl(/** @type {Node} */(obj));
     }
     obj['__domApi'] = helper;
   }
diff --git a/lib/mixins/dir-mixin.js b/lib/mixins/dir-mixin.js
index ffab79705e..3237511791 100644
--- a/lib/mixins/dir-mixin.js
+++ b/lib/mixins/dir-mixin.js
@@ -1,13 +1,14 @@
 /**
+ * @fileoverview
  * @suppress {checkPrototypalTypes}
-@license
-Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
-This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
-The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
-The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
-Code distributed by Google as part of the polymer project is also
-subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-*/
+ * @license Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at
+ * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
+ * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
+ * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
+ * Google as part of the polymer project is also subject to an additional IP
+ * rights grant found at http://polymer.github.io/PATENTS.txt
+ */
 import { PropertyAccessors } from './property-accessors.js';
 
 import { dedupingMixin } from '../utils/mixin.js';
diff --git a/lib/mixins/disable-upgrade-mixin.js b/lib/mixins/disable-upgrade-mixin.js
index 9830907a6e..a97aa9e9ba 100644
--- a/lib/mixins/disable-upgrade-mixin.js
+++ b/lib/mixins/disable-upgrade-mixin.js
@@ -1,13 +1,14 @@
 /**
+ * @fileoverview
  * @suppress {checkPrototypalTypes}
-@license
-Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
-This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
-The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
-The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
-Code distributed by Google as part of the polymer project is also
-subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-*/
+ * @license Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at
+ * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
+ * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
+ * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
+ * Google as part of the polymer project is also subject to an additional IP
+ * rights grant found at http://polymer.github.io/PATENTS.txt
+ */
 import { ElementMixin } from './element-mixin.js';
 
 import { dedupingMixin } from '../utils/mixin.js';
diff --git a/lib/mixins/element-mixin.js b/lib/mixins/element-mixin.js
index e4756ecfd3..c931fb7fc0 100644
--- a/lib/mixins/element-mixin.js
+++ b/lib/mixins/element-mixin.js
@@ -1,13 +1,14 @@
 /**
+ * @fileoverview
  * @suppress {checkPrototypalTypes}
-@license
-Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
-This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
-The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
-The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
-Code distributed by Google as part of the polymer project is also
-subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-*/
+ * @license Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at
+ * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
+ * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
+ * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
+ * Google as part of the polymer project is also subject to an additional IP
+ * rights grant found at http://polymer.github.io/PATENTS.txt
+ */
 import '../utils/boot.js';
 
 import { rootPath, strictTemplatePolicy, allowTemplateFromDomModule, legacyOptimizations, syncInitialRender } from '../utils/settings.js';
@@ -325,7 +326,7 @@ export const ElementMixin = dedupingMixin(base => {
    */
   class PolymerElement extends polymerElementBase {
 
-        /**
+    /**
      * Current Polymer version in Semver notation.
      * @type {string} Semver notation of the current version of Polymer.
      */
@@ -765,6 +766,7 @@ export const ElementMixin = dedupingMixin(base => {
      * @param {Object=} effect Effect metadata object
      * @return {void}
      * @protected
+     * @suppress {missingProperties} Interfaces in closure do not inherit statics, but classes do
      */
     static _addTemplatePropertyEffect(templateInfo, prop, effect) {
       // Warn if properties are used in template without being declared.
diff --git a/lib/mixins/properties-changed.js b/lib/mixins/properties-changed.js
index e70959d251..78ec739ae2 100644
--- a/lib/mixins/properties-changed.js
+++ b/lib/mixins/properties-changed.js
@@ -498,7 +498,7 @@ export const PropertiesChanged = dedupingMixin(
         node.removeAttribute(attribute);
       } else {
         if (attribute === 'class' || attribute === 'name' || attribute === 'slot') {
-          node = wrap(node);
+          node = /** @type {?Element} */(wrap(node));
         }
         node.setAttribute(attribute, str);
       }
diff --git a/lib/mixins/property-accessors.js b/lib/mixins/property-accessors.js
index 074abdea74..bfa7f33a7e 100644
--- a/lib/mixins/property-accessors.js
+++ b/lib/mixins/property-accessors.js
@@ -164,7 +164,7 @@ export const PropertyAccessors = dedupingMixin(superClass => {
      * setter at instance time.  This method is provided as an override
      * point for customizing or providing more efficient initialization.
      *
-     * @param {!Object} props Bag of property values that were overwritten
+     * @param {Object} props Bag of property values that were overwritten
      *   when creating property accessors.
      * @return {void}
      * @protected
diff --git a/lib/mixins/property-effects.js b/lib/mixins/property-effects.js
index a58111b8e9..c92bea3fa6 100644
--- a/lib/mixins/property-effects.js
+++ b/lib/mixins/property-effects.js
@@ -1,13 +1,14 @@
 /**
+ * @fileoverview
  * @suppress {checkPrototypalTypes}
-@license
-Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
-This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
-The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
-The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
-Code distributed by Google as part of the polymer project is also
-subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-*/
+ * @license Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at
+ * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
+ * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
+ * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
+ * Google as part of the polymer project is also subject to an additional IP
+ * rights grant found at http://polymer.github.io/PATENTS.txt
+ */
 
 import '../utils/boot.js';
 import { wrap } from '../utils/wrap.js';
@@ -1172,7 +1173,7 @@ export const PropertyEffects = dedupingMixin(superClass => {
      * the prototype on the instance.
      *
      * @override
-     * @param {!Object} props Properties to initialize on the prototype
+     * @param {Object} props Properties to initialize on the prototype
      * @return {void}
      */
     _initializeProtoProperties(props) {
diff --git a/lib/utils/gestures.js b/lib/utils/gestures.js
index ac529bd2c5..54b2173717 100644
--- a/lib/utils/gestures.js
+++ b/lib/utils/gestures.js
@@ -660,7 +660,7 @@ export function setTouchAction(node, value) {
 function _fire(target, type, detail) {
   let ev = new Event(type, { bubbles: true, cancelable: true, composed: true });
   ev.detail = detail;
-  wrap(target).dispatchEvent(ev);
+  wrap(/** @type {!Node} */(target)).dispatchEvent(ev);
   // forward `preventDefault` in a clean way
   if (ev.defaultPrevented) {
     let preventer = detail.preventer || detail.sourceEvent;
diff --git a/lib/utils/telemetry.js b/lib/utils/telemetry.js
index e28ff54808..5e12c3e5fb 100644
--- a/lib/utils/telemetry.js
+++ b/lib/utils/telemetry.js
@@ -29,7 +29,7 @@ export const registrations = [];
  * @private
  */
 function _regLog(prototype) {
-  console.log('[' + prototype.is + ']: registered');
+  console.log('[' + /** @type {?} */(prototype).is + ']: registered');
 }
 
 /**
diff --git a/lib/utils/templatize.js b/lib/utils/templatize.js
index 4d32535e34..9f05135470 100644
--- a/lib/utils/templatize.js
+++ b/lib/utils/templatize.js
@@ -340,7 +340,7 @@ function createTemplatizerClass(template, templateInfo, options) {
    */
   let templatizerBase = options.mutableData ?
     MutableTemplateInstanceBase : TemplateInstanceBase;
-  
+
   // Affordance for global mixins onto TemplatizeInstance
   if (templatize.mixin) {
     templatizerBase = templatize.mixin(templatizerBase);