diff --git a/lib/Accessibility.js b/lib/Accessibility.js
index 9f005a06b2e35..204fec701e932 100644
--- a/lib/Accessibility.js
+++ b/lib/Accessibility.js
@@ -329,7 +329,9 @@ class AXNode {
       role: this._role
     };
 
-    /** @type {!Array<keyof SerializedAXNode>} */
+    /** @enum {'name'|'value'|'description'|'keyshortcuts'|'roledescription'|'valuetext'} */
+    let UserStringProperties; // eslint-disable-line no-unused-vars
+    /** @type {!Array<UserStringProperties>} */
     const userStringProperties = [
       'name',
       'value',
@@ -338,13 +340,21 @@ class AXNode {
       'roledescription',
       'valuetext',
     ];
+    /**
+     * @param {UserStringProperties} key
+     */
+    const getUserStringPropertyValue = key => /** @type string */(properties.get(key));
+
     for (const userStringProperty of userStringProperties) {
       if (!properties.has(userStringProperty))
         continue;
-      node[userStringProperty] = properties.get(userStringProperty);
+
+      node[userStringProperty] = getUserStringPropertyValue(userStringProperty);
     }
 
-    /** @type {!Array<keyof SerializedAXNode>} */
+    /** @enum {'disabled'|'expanded'|'focused'|'modal'|'multiline'|'multiselectable'|'readonly'|'required'|'selected'} */
+    let BooleanProperties; // eslint-disable-line no-unused-vars
+    /** @type {!Array<BooleanProperties>} */
     const booleanProperties = [
       'disabled',
       'expanded',
@@ -356,18 +366,25 @@ class AXNode {
       'required',
       'selected',
     ];
+    /**
+     * @param {BooleanProperties} key
+     */
+    const getBooleanPropertyValue = key => /** @type boolean */(properties.get(key));
+
     for (const booleanProperty of booleanProperties) {
       // WebArea's treat focus differently than other nodes. They report whether their frame  has focus,
       // not whether focus is specifically on the root node.
       if (booleanProperty === 'focused' && this._role === 'WebArea')
         continue;
-      const value = properties.get(booleanProperty);
+      const value = getBooleanPropertyValue(booleanProperty);
       if (!value)
         continue;
-      node[booleanProperty] = value;
+      node[booleanProperty] = getBooleanPropertyValue(booleanProperty);
     }
 
-    /** @type {!Array<keyof SerializedAXNode>} */
+    /** @enum {'checked'|'pressed'} */
+    let TristateProperties; // eslint-disable-line no-unused-vars
+    /** @type {!Array<TristateProperties>} */
     const tristateProperties = [
       'checked',
       'pressed',
@@ -378,29 +395,45 @@ class AXNode {
       const value = properties.get(tristateProperty);
       node[tristateProperty] = value === 'mixed' ? 'mixed' : value === 'true' ? true : false;
     }
-    /** @type {!Array<keyof SerializedAXNode>} */
+
+
+    /** @enum {'level'|'valuemax'|'valuemin'} */
+    let NumericalProperties; // eslint-disable-line no-unused-vars
+    /** @type {!Array<NumericalProperties>} */
     const numericalProperties = [
       'level',
       'valuemax',
       'valuemin',
     ];
+    /**
+     * @param {NumericalProperties} key
+     */
+    const getNumericalPropertyValue = key => /** @type number */(properties.get(key));
     for (const numericalProperty of numericalProperties) {
       if (!properties.has(numericalProperty))
         continue;
-      node[numericalProperty] = properties.get(numericalProperty);
+      node[numericalProperty] = getNumericalPropertyValue(numericalProperty);
     }
-    /** @type {!Array<keyof SerializedAXNode>} */
+
+
+    /** @enum {'autocomplete'|'haspopup'|'invalid'|'orientation'} */
+    let TokenProperties; // eslint-disable-line no-unused-vars
+    /** @type {!Array<TokenProperties>} */
     const tokenProperties = [
       'autocomplete',
       'haspopup',
       'invalid',
       'orientation',
     ];
+    /**
+     * @param {TokenProperties} key
+     */
+    const getTokenPropertyValue = key => /** @type string */(properties.get(key));
     for (const tokenProperty of tokenProperties) {
-      const value = properties.get(tokenProperty);
+      const value = getTokenPropertyValue(tokenProperty);
       if (!value || value === 'false')
         continue;
-      node[tokenProperty] = value;
+      node[tokenProperty] = getTokenPropertyValue(tokenProperty);
     }
     return node;
   }
diff --git a/lib/Page.js b/lib/Page.js
index 317b9fca996e3..abe1d428d2b55 100644
--- a/lib/Page.js
+++ b/lib/Page.js
@@ -444,8 +444,10 @@ class Page extends EventEmitter {
     await Promise.all(this.frames().map(frame => frame.evaluate(expression).catch(debugError)));
 
     function addPageBinding(bindingName) {
-      const binding = window[bindingName];
-      window[bindingName] = (...args) => {
+      const win = /** @type * */ (window);
+      const binding = /** @type function(string):* */ (win[bindingName]);
+
+      win[bindingName] = (...args) => {
         const me = window[bindingName];
         let callbacks = me['callbacks'];
         if (!callbacks) {
@@ -677,10 +679,12 @@ class Page extends EventEmitter {
    * @return {!Promise<?Puppeteer.Response>}
    */
   async reload(options) {
-    const [response] = await Promise.all([
+    const result = await Promise.all([
       this.waitForNavigation(options),
       this._client.send('Page.reload')
     ]);
+
+    const response = /** @type Puppeteer.Response */ (result[0]);
     return response;
   }
 
@@ -759,10 +763,11 @@ class Page extends EventEmitter {
     const entry = history.entries[history.currentIndex + delta];
     if (!entry)
       return null;
-    const [response] = await Promise.all([
+    const result = await Promise.all([
       this.waitForNavigation(options),
       this._client.send('Page.navigateToHistoryEntry', {entryId: entry.id}),
     ]);
+    const response = /** @type Puppeteer.Response */ (result[0]);
     return response;
   }
 
diff --git a/package.json b/package.json
index 3b354bfccb92f..578cdf5e252e8 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,7 @@
     "lint": "([ \"$CI\" = true ] && eslint --quiet -f codeframe . || eslint .) && npm run tsc && npm run doc",
     "doc": "node utils/doclint/cli.js",
     "coverage": "cross-env COVERAGE=true npm run unit",
-    "tsc": "tsc -p .",
+    "tsc": "tsc --version && tsc -p .",
     "apply-next-version": "node utils/apply_next_version.js",
     "bundle": "npx browserify -r ./index.js:puppeteer -o utils/browser/puppeteer-web.js",
     "test-types": "node utils/doclint/generate_types && npx -p typescript@3.2 tsc -p utils/doclint/generate_types/test/",
@@ -61,7 +61,7 @@
     "pixelmatch": "^4.0.2",
     "pngjs": "^3.3.3",
     "text-diff": "^1.0.1",
-    "typescript": "3.2.2"
+    "typescript": "3.5.3"
   },
   "browser": {
     "./lib/BrowserFetcher.js": false,
diff --git a/utils/doclint/check_public_api/JSBuilder.js b/utils/doclint/check_public_api/JSBuilder.js
index 4892166385afc..d56e4381a63d6 100644
--- a/utils/doclint/check_public_api/JSBuilder.js
+++ b/utils/doclint/check_public_api/JSBuilder.js
@@ -98,7 +98,7 @@ function checkSources(sources) {
   function serializeSymbol(symbol, circular = []) {
     const type = checker.getTypeOfSymbolAtLocation(symbol, symbol.valueDeclaration);
     const name = symbol.getName();
-    if (symbol.valueDeclaration.dotDotDotToken) {
+    if (symbol.valueDeclaration && symbol.valueDeclaration.dotDotDotToken) {
       const innerType = serializeType(type.typeArguments[0], circular);
       innerType.name = '...' + innerType.name;
       return Documentation.Member.createProperty('...' + name, innerType);
@@ -120,6 +120,12 @@ function checkSources(sources) {
       return false;
     if (type.getCallSignatures().length)
       return false;
+    if (type.isLiteral())
+      return false;
+    if (type.isUnion())
+      return false;
+
+
     return true;
   }