Upgrade TypeScript to 3.3.

frontend/lib/app-context.tsx

@@ -145,9 +145,11 @@ export const AppContext = React.createContext<AppContextType>(defaultContext);
  */
 export function withAppContext<P extends AppContextType>(Component: React.ComponentType<P>): React.ComponentType<Omit<P, keyof AppContextType>> {
   return function(props: Omit<P, keyof AppContextType>) {
+    // https://github.com/Microsoft/TypeScript/issues/28748
+    const tsIssue28748Workaround = props as any;
     return (
       <AppContext.Consumer>
-        {(context) => <Component {...props} {...context} />}
+        {(context) => <Component {...tsIssue28748Workaround} {...context} />}
       </AppContext.Consumer>
     );
   }

frontend/lib/aria.tsx

@@ -81,9 +81,11 @@ export const AriaContext = React.createContext<AriaContextType>({
 
 function withAriaContext<P extends AriaContextType>(Component: React.ComponentType<P>): React.ComponentType<Omit<P, keyof AriaContextType>> {
   return function(props: Omit<P, keyof AriaContextType>) {
+    // https://github.com/Microsoft/TypeScript/issues/28748
+    const tsIssue28748Workaround = props as any;
     return (
       <AriaContext.Consumer>
-        {(context) => <Component {...props} announce={context.announce} />}
+        {(context) => <Component {...tsIssue28748Workaround} announce={context.announce} />}
       </AriaContext.Consumer>
     );
   }

frontend/lib/faceboox-pixel.ts

@@ -32,6 +32,6 @@ declare global {
  */
 export const fbq: FacebookPixelAPI = function fbq() {
   if (typeof(window) !== 'undefined' && typeof(window.fbq) === 'function') {
-    window.fbq.apply(window, arguments);
+    window.fbq.apply(window, arguments as any);
   }
 };

frontend/lib/fetch.ts

@@ -21,12 +21,16 @@ export function dynamicallyImportFetch(): Promise<typeof fetch> {
  * Just like window.fetch(), but dynamically loads a polyfill
  * if needed.
  */
-export const awesomeFetch: typeof fetch = function(this: any) {
+export const awesomeFetch: typeof fetch = function(
+  this: any,
+  input: RequestInfo,
+  init?: RequestInit | undefined
+): Promise<Response> {
   if (typeof(fetch) === 'function') {
-    return fetch.apply(this, arguments);
+    return fetch.apply(this, [input, init]);
   }
   return dynamicallyImportFetch().then(fetch => {
-    return fetch.apply(this, arguments);
+    return fetch.apply(this, [input, init]);
   });
 };
 

frontend/lib/google-analytics.tsx

@@ -169,7 +169,12 @@ function callAnyHitCallbacks(args: unknown[]) {
  */
 export const ga: GoogleAnalyticsAPI = function ga() {
   if (typeof(window) !== 'undefined' && typeof(window.ga) === 'function') {
-    window.ga.apply(window, arguments);
+    // We're typecasting arguments as "any" here because as of TS 3.2,
+    // apply() can't fully model functions that have overloads, which is what
+    // ga() is.  However, the fact that we're returning an object that's
+    // strongly typed means that type safety is still ensured where it matters
+    // most.
+    window.ga.apply(window, arguments as any);
   } else {
     callAnyHitCallbacks(Array.from(arguments));
   }

frontend/lib/loading-page.tsx

@@ -165,7 +165,7 @@ class LoadingOverlayManagerWithoutRouter extends React.Component<LoadingOverlayM
       if (div && this.state.latestSnapshot) {
         div.innerHTML = '';
         div.appendChild(this.state.latestSnapshot.div);
-        window.scroll({ top: this.state.latestSnapshot.scroll, left: 0, behavior: 'instant' });
+        window.scroll({ top: this.state.latestSnapshot.scroll, left: 0, behavior: 'auto' });
       }
     } else if (prevState.showOverlay === true && this.state.showOverlay === false) {
       // We just stopped showing the overlay, so make sure the top of the page

frontend/lib/progress-bar.tsx

@@ -1,6 +1,6 @@
 import React from 'react';
 import autobind from "autobind-decorator";
-import { RouteComponentProps, withRouter, Route, Switch } from 'react-router';
+import { RouteComponentProps, withRouter, Route, RouteProps, Switch } from 'react-router';
 import { CSSTransition } from 'react-transition-group';
 import { TransitionContextGroup } from './transition-context';
 import classnames from 'classnames';
@@ -181,7 +181,7 @@ class RouteProgressBarWithoutRouter extends React.Component<RouteProgressBarProp
           <CSSTransition key={currStep} classNames="jf-progress-step"
            timeout={JF_PROGRESS_TRANSITION_MS} enter={isTransitionEnabled} exit={isTransitionEnabled}>
             <Switch location={location}>
-              {props.steps.map(step => <Route key={step.path} {...step} />)}
+              {props.steps.map(step => <Route<RouteProps> key={step.path} {...step} />)}
             </Switch>
           </CSSTransition>
         </TransitionContextGroup>

frontend/lib/tests/setup.ts

@@ -37,8 +37,8 @@ const originalLog = console.log;
  * Combined with the general sluggishness of Jest on Windows, I'm
  * very much regretting not using Mocha at this point.
  */
-console.log = function() {
-  originalLog.apply(this, arguments);
+console.log = function(message?: any, ...optionalParams: any[]) {
+  originalLog.apply(this, [message, ...optionalParams]);
   originalLog.call(this, chalk.green('\n ^^^ SOMETHING GOT LOGGED! ^^^\n'));
 };
 

frontend/lib/transition-context.tsx

@@ -49,9 +49,11 @@ export function TransitionContextGroup(props: TransitionContextGroupProps): JSX.
  */
 export function withTransitionContext<P extends TransitionContextType>(Component: React.ComponentType<P>): React.ComponentType<Omit<P, keyof TransitionContextType>> {
   return function(props: Omit<P, keyof TransitionContextType>) {
+    // https://github.com/Microsoft/TypeScript/issues/28748
+    const tsIssue28748Workaround = props as any;
     return (
       <TransitionContext.Consumer>
-        {(context) => <Component {...props} {...context} />}
+        {(context) => <Component {...tsIssue28748Workaround} {...context} />}
       </TransitionContext.Consumer>
     );
   }

package.json

@@ -92,7 +92,7 @@
     "smoothscroll-polyfill": "0.4.3",
     "source-map-support": "0.5.9",
     "ts-loader": "4.5.0",
-    "typescript": "3.1.6",
+    "typescript": "3.3.1",
     "uglify-js": "3.4.9",
     "webpack": "4.23.1",
     "webpack-cli": "3.1.2",