diff --git a/lib/legacy/class.html b/lib/legacy/class.html
index 10cf73b449..d2e0fc1110 100644
--- a/lib/legacy/class.html
+++ b/lib/legacy/class.html
@@ -42,7 +42,8 @@
      */
     function mixinBehaviors(behaviors, klass) {
       if (!behaviors) {
-        return /** @type {HTMLElement} */(klass);
+        klass = /** @type {HTMLElement} */(klass); // eslint-disable-line no-self-assign
+        return klass;
       }
       // NOTE: ensure the behavior is extending a class with
       // legacy element api. This is necessary since behaviors expect to be able
diff --git a/lib/legacy/legacy-element-mixin.html b/lib/legacy/legacy-element-mixin.html
index faceefe9e7..742bbf9907 100644
--- a/lib/legacy/legacy-element-mixin.html
+++ b/lib/legacy/legacy-element-mixin.html
@@ -479,7 +479,8 @@
        * @return {Array<Node>} List of effective child nodes.
        */
       getEffectiveChildNodes() {
-        return /** @type {Polymer.DomApi} */ (Polymer.dom(this)).getEffectiveChildNodes();
+        const domApi = /** @type {Polymer.DomApi} */(Polymer.dom(this));
+        return domApi.getEffectiveChildNodes();
       }
 
       /**
@@ -491,7 +492,8 @@
        * @return {Array<Node>} List of distributed elements that match selector.
        */
       queryDistributedElements(selector) {
-        return /** @type {Polymer.DomApi} */ (Polymer.dom(this)).queryDistributedElements(selector);
+        const domApi = /** @type {Polymer.DomApi} */(Polymer.dom(this));
+        return domApi.queryDistributedElements(selector);
       }
 
       /**
@@ -581,9 +583,10 @@
        * @suppress {invalidCasts}
        */
       getContentChildren(slctr) {
-        return /** @type {Array<HTMLElement>} */(this.getContentChildNodes(slctr).filter(function(n) {
+        let children = /** @type {Array<HTMLElement>} */(this.getContentChildNodes(slctr).filter(function(n) {
           return (n.nodeType === Node.ELEMENT_NODE);
         }));
+        return children;
       }
 
       /**
diff --git a/lib/legacy/mutable-data-behavior.html b/lib/legacy/mutable-data-behavior.html
index 4fb70cb53c..850edf185b 100644
--- a/lib/legacy/mutable-data-behavior.html
+++ b/lib/legacy/mutable-data-behavior.html
@@ -15,9 +15,8 @@
   'use strict';
 
   let mutablePropertyChange;
-  (
-    /** @suppress {missingProperties} */
-    function() {
+  /** @suppress {missingProperties} */
+  (() => {
     mutablePropertyChange = Polymer.MutableData._mutablePropertyChange;
   })();
 
diff --git a/lib/legacy/polymer.dom.html b/lib/legacy/polymer.dom.html
index c15820c430..f86596b1e9 100644
--- a/lib/legacy/polymer.dom.html
+++ b/lib/legacy/polymer.dom.html
@@ -205,7 +205,8 @@
       let name = properties[i];
       Object.defineProperty(proto, name, {
         get: function() {
-          return /** @type {DomApi} */ (this).node[name];
+          const domApi = /** @type {DomApi} */(this);
+          return domApi.node[name];
         },
         configurable: true
       });
@@ -217,7 +218,8 @@
       let name = properties[i];
       Object.defineProperty(proto, name, {
         get: function() {
-          return /** @type {DomApi} */ (this).node[name];
+          const domApi = /** @type {DomApi} */(this);
+          return domApi.node[name];
         },
         set: function(value) {
           /** @type {DomApi} */ (this).node[name] = value;
diff --git a/lib/mixins/property-accessors.html b/lib/mixins/property-accessors.html
index 3851a1e426..15900ab7bc 100644
--- a/lib/mixins/property-accessors.html
+++ b/lib/mixins/property-accessors.html
@@ -605,12 +605,8 @@
        * @protected
        */
       _shouldPropertyChange(property, value, old) {
-        return (
-          // Strict equality check
-          (old !== value &&
-           // This ensures (old==NaN, value==NaN) always returns false
-           (old === old || value === value))
-        );
+        // check equality, and ensure (old == NaN, value == NaN) always returns false
+        return old !== value && (old === old || value === value);
       }
 
     }
diff --git a/lib/mixins/template-stamp.html b/lib/mixins/template-stamp.html
index f277ff6a6b..aed815c46f 100644
--- a/lib/mixins/template-stamp.html
+++ b/lib/mixins/template-stamp.html
@@ -429,7 +429,8 @@
           applyTemplateContent(this, node, info);
           applyEventListener(this, node, info);
         }
-        return /** @type {!StampedTemplate} */(dom);
+        dom = /** @type {!StampedTemplate} */(dom); // eslint-disable-line no-self-assign
+        return dom;
       }
 
       /**
diff --git a/lib/utils/flattened-nodes-observer.html b/lib/utils/flattened-nodes-observer.html
index 78742e3578..5ea0085a4e 100644
--- a/lib/utils/flattened-nodes-observer.html
+++ b/lib/utils/flattened-nodes-observer.html
@@ -64,11 +64,13 @@
     */
     static getFlattenedNodes(node) {
       if (isSlot(node)) {
-        return /** @type {HTMLSlotElement} */ (node).assignedNodes({flatten: true});
+        node = /** @type {HTMLSlotElement} */(node); // eslint-disable-line no-self-assign
+        return node.assignedNodes({flatten: true});
       } else {
-        return Array.from(node.childNodes).map(node => {
+        return Array.from(node.childNodes).map((node) => {
           if (isSlot(node)) {
-            return /** @type {HTMLSlotElement} */ (node).assignedNodes({flatten: true});
+            node = /** @type {HTMLSlotElement} */(node); // eslint-disable-line no-self-assign
+            return node.assignedNodes({flatten: true});
           } else {
             return [node];
           }
diff --git a/lib/utils/gestures.html b/lib/utils/gestures.html
index ea2e29c4be..b741455a9d 100644
--- a/lib/utils/gestures.html
+++ b/lib/utils/gestures.html
@@ -311,7 +311,8 @@
     _findOriginalTarget: function(ev) {
       // shadowdom
       if (ev.composedPath) {
-        return /** @type {EventTarget} */(ev.composedPath()[0]);
+        const target = /** @type {EventTarget} */(ev.composedPath()[0]);
+        return target;
       }
       // shadydom
       return ev.target;
diff --git a/lib/utils/templatize.html b/lib/utils/templatize.html
index ef7eead5be..8723f9c9b5 100644
--- a/lib/utils/templatize.html
+++ b/lib/utils/templatize.html
@@ -466,7 +466,8 @@
         klass.prototype.__dataHost = template;
         klass.prototype.__templatizeOwner = owner;
         klass.prototype.__hostProps = templateInfo.hostProps;
-        return /** @type {function(new:TemplateInstanceBase)} */(klass);
+        klass = /** @type {function(new:TemplateInstanceBase)} */(klass); //eslint-disable-line no-self-assign
+        return klass;
       },
 
       /**