Prefer type to interface and add an ESLint rule

.eslintrc.js

@@ -95,6 +95,36 @@ const rules = {
 
   // Upgrade from a warning
   '@typescript-eslint/explicit-module-boundary-types': 'error',
+
+  'no-restricted-syntax': [
+    'error',
+    {
+      selector: 'TSInterfaceDeclaration',
+      message:
+        'Prefer `type`. Interfaces are mutable and less powerful, so we prefer `type` for simplicity.',
+    },
+    // Defaults
+    {
+      selector: 'ForInStatement',
+      message:
+        'for..in loops iterate over the entire prototype chain, which is virtually never what you want. Use Object.{keys,values,entries}, and iterate over the resulting array.',
+    },
+    {
+      selector: 'ForOfStatement',
+      message:
+        'iterators/generators require regenerator-runtime, which is too heavyweight for this guide to allow them. Separately, loops should be avoided in favor of array iterations.',
+    },
+    {
+      selector: 'LabeledStatement',
+      message:
+        'Labels are a form of GOTO; using them makes code confusing and hard to maintain and understand.',
+    },
+    {
+      selector: 'WithStatement',
+      message:
+        '`with` is disallowed in strict mode because it makes code impossible to predict and optimize.',
+    },
+  ],
 };
 
 module.exports = {

sticker-creator/root.tsx

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { hot } from 'react-hot-loader/root';
@@ -11,6 +11,8 @@ import { store } from './store';
 import { I18n } from './util/i18n';
 
 declare global {
+  // We want to extend `window` here.
+  // eslint-disable-next-line no-restricted-syntax
   interface Window {
     localeMessages: { [key: string]: { message: string } };
   }

sticker-creator/store/ducks/stickers.ts

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable no-param-reassign */
@@ -56,15 +56,15 @@ export const minStickers = 1;
 export const maxStickers = 200;
 export const maxByteSize = 300 * 1024;
 
-interface StateStickerData {
+type StateStickerData = {
   readonly imageData?: StickerImageData;
   readonly emoji?: EmojiPickDataType;
-}
+};
 
-interface StateToastData {
+type StateToastData = {
   key: string;
   subs?: Array<number | string>;
-}
+};
 
 export type State = {
   readonly order: Array<string>;

sticker-creator/util/preload.ts

@@ -1,9 +1,11 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { Metadata } from 'sharp';
 
 declare global {
+  // We want to extend `window`'s properties, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Window {
     processStickerImage: ProcessStickerImageFn;
     encryptAndUpload: EncryptAndUploadFn;

ts/components/Avatar.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as React from 'react';
@@ -37,10 +37,10 @@ export type Props = {
   i18n: LocalizerType;
 } & Pick<React.HTMLProps<HTMLDivElement>, 'className'>;
 
-interface State {
+type State = {
-  imageBroken: boolean;
+  readonly imageBroken: boolean;
-  lastAvatarPath?: string;
+  readonly lastAvatarPath?: string;
-}
+};
 
 export class Avatar extends React.Component<Props, State> {
   public handleImageErrorBound: () => void;

ts/components/CallManager.tsx

@@ -39,11 +39,11 @@ import {
 import { LocalizerType } from '../types/Util';
 import { missingCaseError } from '../util/missingCaseError';
 
-interface MeType extends ConversationType {
+type MeType = ConversationType & {
   uuid: string;
-}
+};
 
-export interface PropsType {
+export type PropsType = {
   activeCall?: ActiveCallType;
   availableCameras: Array<MediaDeviceInfo>;
   cancelCall: (_: CancelCallType) => void;
@@ -74,11 +74,11 @@ export interface PropsType {
   togglePip: () => void;
   toggleSettings: () => void;
   toggleSpeakerView: () => void;
-}
+};
 
-interface ActiveCallManagerPropsType extends PropsType {
+type ActiveCallManagerPropsType = PropsType & {
   activeCall: ActiveCallType;
-}
+};
 
 const ActiveCallManager: React.FC<ActiveCallManagerPropsType> = ({
   activeCall,

ts/components/CallNeedPermissionScreen.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React, { useRef, useEffect } from 'react';
@@ -8,7 +8,7 @@ import { Intl } from './Intl';
 import { ContactName } from './conversation/ContactName';
 import { ColorType } from '../types/Colors';
 
-interface Props {
+type Props = {
   conversation: {
     avatarPath?: string;
     color?: ColorType;
@@ -19,7 +19,7 @@ interface Props {
   };
   i18n: LocalizerType;
   close: () => void;
-}
+};
 
 const AUTO_CLOSE_MS = 10000;
 

ts/components/CallScreen.stories.tsx

@@ -41,24 +41,24 @@ const conversation = {
   lastUpdated: Date.now(),
 };
 
-interface OverridePropsBase {
+type OverridePropsBase = {
   hasLocalAudio?: boolean;
   hasLocalVideo?: boolean;
   isInSpeakerView?: boolean;
-}
+};
 
-interface DirectCallOverrideProps extends OverridePropsBase {
+type DirectCallOverrideProps = OverridePropsBase & {
   callMode: CallMode.Direct;
   callState?: CallState;
   hasRemoteVideo?: boolean;
-}
+};
 
-interface GroupCallOverrideProps extends OverridePropsBase {
+type GroupCallOverrideProps = OverridePropsBase & {
   callMode: CallMode.Group;
   connectionState?: GroupCallConnectionState;
   peekedParticipants?: Array<ConversationType>;
   remoteParticipants?: Array<GroupCallRemoteParticipantType>;
-}
+};
 
 const createActiveDirectCallProp = (
   overrideProps: DirectCallOverrideProps

ts/components/CallingParticipantsList.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable react/no-array-index-key */
@@ -12,10 +12,10 @@ import { LocalizerType } from '../types/Util';
 import { sortByTitle } from '../util/sortByTitle';
 import { ConversationType } from '../state/ducks/conversations';
 
-interface ParticipantType extends ConversationType {
+type ParticipantType = ConversationType & {
   hasAudio?: boolean;
   hasVideo?: boolean;
-}
+};
 
 export type PropsType = {
   readonly i18n: LocalizerType;

ts/components/CallingPip.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -42,14 +42,14 @@ type PositionState =
       offsetX: number;
     };
 
-interface SnapCandidate {
+type SnapCandidate = {
   mode:
     | PositionMode.SnapToBottom
     | PositionMode.SnapToLeft
     | PositionMode.SnapToRight
     | PositionMode.SnapToTop;
   distanceToEdge: number;
-}
+};
 
 export type PropsType = {
   activeCall: ActiveCallType;

ts/components/CallingPipRemoteVideo.tsx

@@ -61,13 +61,13 @@ const NoVideo = ({
   );
 };
 
-export interface PropsType {
+export type PropsType = {
   activeCall: ActiveCallType;
   getGroupCallVideoFrameSource: (demuxId: number) => VideoFrameSource;
   i18n: LocalizerType;
   setGroupCallVideoRequest: (_: Array<GroupCallVideoRequest>) => void;
   setRendererCanvas: (_: SetRendererCanvasType) => void;
-}
+};
 
 export const CallingPipRemoteVideo = ({
   activeCall,

ts/components/CaptionEditor.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -8,18 +8,18 @@ import { AttachmentType } from '../types/Attachment';
 
 import { LocalizerType } from '../types/Util';
 
-export interface Props {
+export type Props = {
   attachment: AttachmentType;
   i18n: LocalizerType;
   url: string;
   caption?: string;
   onSave?: (caption: string) => void;
   close?: () => void;
-}
+};
 
-interface State {
+type State = {
   caption: string;
-}
+};
 
 export class CaptionEditor extends React.Component<Props, State> {
   private readonly handleKeyDownBound: (

ts/components/CompositionInput.tsx

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as React from 'react';
@@ -42,20 +42,20 @@ Quill.register('modules/emojiCompletion', EmojiCompletion);
 Quill.register('modules/mentionCompletion', MentionCompletion);
 Quill.register('modules/signalClipboard', SignalClipboard);
 
-interface HistoryStatic {
+type HistoryStatic = {
   undo(): void;
   clear(): void;
-}
+};
 
-export interface InputApi {
+export type InputApi = {
   focus: () => void;
   insertEmoji: (e: EmojiPickDataType) => void;
   reset: () => void;
   resetEmojiResults: () => void;
   submit: () => void;
-}
+};
 
-export interface Props {
+export type Props = {
   readonly i18n: LocalizerType;
   readonly disabled?: boolean;
   readonly large?: boolean;
@@ -75,7 +75,7 @@ export interface Props {
   onSubmit(message: string, mentions: Array<BodyRangeType>): unknown;
   getQuotedMessage(): unknown;
   clearQuotedMessage(): unknown;
-}
+};
 
 const MAX_LENGTH = 64 * 1024;
 

ts/components/ContactListItem.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -11,7 +11,7 @@ import { InContactsIcon } from './InContactsIcon';
 import { LocalizerType } from '../types/Util';
 import { ColorType } from '../types/Colors';
 
-interface Props {
+type Props = {
   avatarPath?: string;
   color?: ColorType;
   i18n: LocalizerType;
@@ -23,7 +23,7 @@ interface Props {
   phoneNumber?: string;
   profileName?: string;
   title: string;
-}
+};
 
 export class ContactListItem extends React.Component<Props> {
   public renderAvatar(): JSX.Element {

ts/components/Countdown.tsx

@@ -1,16 +1,16 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
 
-export interface Props {
+export type Props = {
   duration: number;
   expiresAt: number;
   onComplete?: () => unknown;
-}
+};
-interface State {
+type State = {
   ratio: number;
-}
+};
 
 const CIRCUMFERENCE = 11.013 * 2 * Math.PI;
 

ts/components/DirectCallRemoteParticipant.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React, { useRef, useEffect } from 'react';
@@ -8,12 +8,12 @@ import { ColorType } from '../types/Colors';
 import { LocalizerType } from '../types/Util';
 import { Avatar } from './Avatar';
 
-interface PropsType {
+type PropsType = {
   conversation: ConversationType;
   hasRemoteVideo: boolean;
   i18n: LocalizerType;
   setRendererCanvas: (_: SetRendererCanvasType) => void;
-}
+};
 
 export const DirectCallRemoteParticipant: React.FC<PropsType> = ({
   conversation,

ts/components/ExpiredBuildDialog.tsx

@@ -1,14 +1,14 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
 
 import { LocalizerType } from '../types/Util';
 
-interface PropsType {
+type PropsType = {
   hasExpired: boolean;
   i18n: LocalizerType;
-}
+};
 
 export const ExpiredBuildDialog = ({
   hasExpired,

ts/components/GroupCallOverflowArea.tsx

@@ -16,12 +16,12 @@ const OVERFLOW_SCROLL_BUTTON_RATIO = 0.75;
 // This should be an integer, as sub-pixel widths can cause performance issues.
 export const OVERFLOW_PARTICIPANT_WIDTH = 140;
 
-interface PropsType {
+type PropsType = {
   getFrameBuffer: () => ArrayBuffer;
   getGroupCallVideoFrameSource: (demuxId: number) => VideoFrameSource;
   i18n: LocalizerType;
   overflowedParticipants: ReadonlyArray<GroupCallRemoteParticipantType>;
-}
+};
 
 export const GroupCallOverflowArea: FC<PropsType> = ({
   getFrameBuffer,

ts/components/GroupCallRemoteParticipant.tsx

@@ -24,27 +24,27 @@ import { ContactName } from './conversation/ContactName';
 import { useIntersectionObserver } from '../util/hooks';
 import { MAX_FRAME_SIZE } from '../calling/constants';
 
-interface BasePropsType {
+type BasePropsType = {
   getFrameBuffer: () => ArrayBuffer;
   getGroupCallVideoFrameSource: (demuxId: number) => VideoFrameSource;
   i18n: LocalizerType;
   remoteParticipant: GroupCallRemoteParticipantType;
-}
+};
 
-interface InPipPropsType {
+type InPipPropsType = {
   isInPip: true;
-}
+};
 
-interface InOverflowAreaPropsType {
+type InOverflowAreaPropsType = {
   height: number;
   isInPip?: false;
   width: number;
-}
+};
 
-interface InGridPropsType extends InOverflowAreaPropsType {
+type InGridPropsType = InOverflowAreaPropsType & {
   left: number;
   top: number;
-}
+};
 
 export type PropsType = BasePropsType &
   (InPipPropsType | InOverflowAreaPropsType | InGridPropsType);

ts/components/GroupCallRemoteParticipants.tsx

@@ -25,23 +25,23 @@ const PARTICIPANT_MARGIN = 10;
 // We scale our video requests down for performance. This number is somewhat arbitrary.
 const VIDEO_REQUEST_SCALAR = 0.75;
 
-interface Dimensions {
+type Dimensions = {
   width: number;
   height: number;
-}
+};
 
-interface GridArrangement {
+type GridArrangement = {
   rows: Array<Array<GroupCallRemoteParticipantType>>;
   scalar: number;
-}
+};
 
-interface PropsType {
+type PropsType = {
   getGroupCallVideoFrameSource: (demuxId: number) => VideoFrameSource;
   i18n: LocalizerType;
   isInSpeakerView: boolean;
   remoteParticipants: ReadonlyArray<GroupCallRemoteParticipantType>;
   setGroupCallVideoRequest: (_: Array<GroupCallVideoRequest>) => void;
-}
+};
 
 // This component lays out group call remote participants. It uses a custom layout
 //   algorithm (in other words, nothing that the browser provides, like flexbox) in

ts/components/GroupCallToastManager.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React, { useState, useEffect } from 'react';
@@ -6,10 +6,10 @@ import classNames from 'classnames';
 import { GroupCallConnectionState } from '../types/Calling';
 import { LocalizerType } from '../types/Util';
 
-interface PropsType {
+type PropsType = {
   connectionState: GroupCallConnectionState;
   i18n: LocalizerType;
-}
+};
 
 // In the future, this component should show toasts when users join or leave. See
 //   DESKTOP-902.

ts/components/Intl.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -8,13 +8,13 @@ import { ReplacementValuesType } from '../types/I18N';
 
 export type FullJSXType = Array<JSX.Element | string> | JSX.Element | string;
 
-export interface Props {
+export type Props = {
   /** The translation string id */
   id: string;
   i18n: LocalizerType;
   components?: Array<FullJSXType> | ReplacementValuesType<FullJSXType>;
   renderText?: RenderTextCallbackType;
-}
+};
 
 export class Intl extends React.Component<Props> {
   public static defaultProps: Partial<Props> = {

ts/components/LeftPane.tsx

@@ -17,7 +17,7 @@ import {
 import { LocalizerType } from '../types/Util';
 import { cleanId } from './_util';
 
-export interface PropsType {
+export type PropsType = {
   conversations?: Array<ConversationListItemPropsType>;
   archivedConversations?: Array<ConversationListItemPropsType>;
   pinnedConversations?: Array<ConversationListItemPropsType>;
@@ -43,7 +43,7 @@ export interface PropsType {
   renderNetworkStatus: () => JSX.Element;
   renderRelinkDialog: () => JSX.Element;
   renderUpdateDialog: () => JSX.Element;
-}
+};
 
 // from https://github.com/bvaughn/react-virtualized/blob/fb3484ed5dcc41bffae8eab029126c0fb8f7abc0/source/List/types.js#L5
 type RowRendererParamsType = {
@@ -69,26 +69,26 @@ export enum HeaderType {
   Chats,
 }
 
-interface ArchiveButtonRow {
+type ArchiveButtonRow = {
   type: RowType.ArchiveButton;
-}
+};
 
-interface ConversationRow {
+type ConversationRow = {
   index: number;
   type:
     | RowType.ArchivedConversation
     | RowType.Conversation
     | RowType.PinnedConversation;
-}
+};
 
-interface HeaderRow {
+type HeaderRow = {
   headerType: HeaderType;
   type: RowType.Header;
-}
+};
 
-interface UndefinedRow {
+type UndefinedRow = {
   type: RowType.Undefined;
-}
+};
 
 type Row = ArchiveButtonRow | ConversationRow | HeaderRow | UndefinedRow;
 

ts/components/Lightbox.tsx

@@ -24,7 +24,7 @@ const colorSVG = (url: string, color: string) => {
   };
 };
 
-export interface Props {
+export type Props = {
   close: () => void;
   contentType: MIME.MIMEType | undefined;
   i18n: LocalizerType;
@@ -34,10 +34,10 @@ export interface Props {
   onNext?: () => void;
   onPrevious?: () => void;
   onSave?: () => void;
-}
+};
-interface State {
+type State = {
   videoTime?: number;
-}
+};
 
 const CONTROLS_WIDTH = 50;
 const CONTROLS_SPACING = 10;
@@ -158,12 +158,12 @@ const styles = {
   },
 };
 
-interface IconButtonProps {
+type IconButtonProps = {
   i18n: LocalizerType;
   onClick?: () => void;
   style?: React.CSSProperties;
   type: 'save' | 'close' | 'previous' | 'next';
-}
+};
 
 const IconButton = ({ i18n, onClick, style, type }: IconButtonProps) => {
   const clickHandler = (event: React.MouseEvent<HTMLButtonElement>): void => {

ts/components/LightboxGallery.tsx

@@ -10,16 +10,16 @@ import { Message } from './conversation/media-gallery/types/Message';
 import { AttachmentType } from '../types/Attachment';
 import { LocalizerType } from '../types/Util';
 
-export interface MediaItemType {
+export type MediaItemType = {
   objectURL?: string;
   thumbnailObjectUrl?: string;
   contentType?: MIME.MIMEType;
   index: number;
   attachment: AttachmentType;
   message: Message;
-}
+};
 
-export interface Props {
+export type Props = {
   close: () => void;
   i18n: LocalizerType;
   media: Array<MediaItemType>;
@@ -29,11 +29,11 @@ export interface Props {
     index: number;
   }) => void;
   selectedIndex: number;
-}
+};
 
-interface State {
+type State = {
   selectedIndex: number;
-}
+};
 
 export class LightboxGallery extends React.Component<Props, State> {
   public static defaultProps: Partial<Props> = {

ts/components/MainHeader.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -13,7 +13,7 @@ import { AvatarPopup } from './AvatarPopup';
 import { LocalizerType } from '../types/Util';
 import { ColorType } from '../types/Colors';
 
-export interface PropsType {
+export type PropsType = {
   searchTerm: string;
   searchConversationName?: string;
   searchConversationId?: string;
@@ -58,12 +58,12 @@ export interface PropsType {
   clearSearch: () => void;
 
   showArchivedConversations: () => void;
-}
+};
 
-interface StateType {
+type StateType = {
   showingAvatarPopup: boolean;
   popperRoot: HTMLDivElement | null;
-}
+};
 
 export class MainHeader extends React.Component<PropsType, StateType> {
   private readonly inputRef: React.RefObject<HTMLInputElement>;

ts/components/MessageBodyHighlight.tsx

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -11,10 +11,10 @@ import { SizeClassType } from './emoji/lib';
 
 import { LocalizerType, RenderTextCallbackType } from '../types/Util';
 
-export interface Props {
+export type Props = {
   text: string;
   i18n: LocalizerType;
-}
+};
 
 const renderNewLines: RenderTextCallbackType = ({ text, key }) => (
   <AddNewLines key={key} text={text} />

ts/components/NetworkStatus.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -8,11 +8,11 @@ import { NetworkStateType } from '../state/ducks/network';
 
 const FIVE_SECONDS = 5 * 1000;
 
-export interface PropsType extends NetworkStateType {
+export type PropsType = NetworkStateType & {
   hasNetworkDialog: boolean;
   i18n: LocalizerType;
   manualReconnect: () => void;
-}
+};
 
 type RenderDialogTypes = {
   title: string;

ts/components/RelinkDialog.tsx

@@ -1,15 +1,15 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
 
 import { LocalizerType } from '../types/Util';
 
-export interface PropsType {
+export type PropsType = {
   i18n: LocalizerType;
   isRegistrationDone: boolean;
   relinkDevice: () => void;
-}
+};
 
 export const RelinkDialog = ({
   i18n,

ts/components/Spinner.tsx

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -15,11 +15,11 @@ export const SpinnerDirections = [
 ] as const;
 export type SpinnerDirection = typeof SpinnerDirections[number];
 
-export interface Props {
+export type Props = {
   size?: string;
   svgSize: SpinnerSvgSize;
   direction?: SpinnerDirection;
-}
+};
 
 export const Spinner = ({ size, svgSize, direction }: Props): JSX.Element => (
   <div

ts/components/StartNewConversation.tsx

@@ -7,11 +7,11 @@ import { Avatar } from './Avatar';
 
 import { LocalizerType } from '../types/Util';
 
-export interface Props {
+export type Props = {
   phoneNumber: string;
   i18n: LocalizerType;
   onClick: () => void;
-}
+};
 
 export class StartNewConversation extends React.PureComponent<Props> {
   public render(): JSX.Element {

ts/components/Tooltip.tsx

@@ -7,10 +7,10 @@ import { noop } from 'lodash';
 import { Manager, Reference, Popper } from 'react-popper';
 import { Theme, themeClassName } from '../util/theme';
 
-interface EventWrapperPropsType {
+type EventWrapperPropsType = {
   children: React.ReactNode;
   onHoverChanged: (_: boolean) => void;
-}
+};
 
 // React doesn't reliably fire `onMouseLeave` or `onMouseOut` events if wrapping a
 //   disabled button. This uses native browser events to avoid that.

ts/components/UpdateDialog.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -7,7 +7,7 @@ import { Dialogs } from '../types/Dialogs';
 import { Intl } from './Intl';
 import { LocalizerType } from '../types/Util';
 
-export interface PropsType {
+export type PropsType = {
   ackRender: () => void;
   dialogType: Dialogs;
   didSnooze: boolean;
@@ -17,7 +17,7 @@ export interface PropsType {
   showEventsCount: number;
   snoozeUpdate: () => void;
   startUpdate: () => void;
-}
+};
 
 export const UpdateDialog = ({
   ackRender,

ts/components/conversation/AddNewLines.tsx

@@ -5,11 +5,11 @@ import React from 'react';
 
 import { RenderTextCallbackType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   text: string;
   /** Allows you to customize now non-newlines are rendered. Simplest is just a <span>. */
   renderNonNewLine?: RenderTextCallbackType;
-}
+};
 
 export class AddNewLines extends React.Component<Props> {
   public static defaultProps: Partial<Props> = {

ts/components/conversation/AttachmentList.tsx

@@ -15,14 +15,14 @@ import {
   isVideoAttachment,
 } from '../../types/Attachment';
 
-export interface Props {
+export type Props = {
   attachments: Array<AttachmentType>;
   i18n: LocalizerType;
   onClickAttachment: (attachment: AttachmentType) => void;
   onCloseAttachment: (attachment: AttachmentType) => void;
   onAddAttachment: () => void;
   onClose: () => void;
-}
+};
 
 const IMAGE_WIDTH = 120;
 const IMAGE_HEIGHT = 120;

ts/components/conversation/CallingNotification.tsx

@@ -14,14 +14,14 @@ import {
 import { missingCaseError } from '../../util/missingCaseError';
 import { Tooltip, TooltipPlacement } from '../Tooltip';
 
-export interface PropsActionsType {
+export type PropsActionsType = {
   messageSizeChanged: (messageId: string, conversationId: string) => void;
   returnToActiveCall: () => void;
   startCallingLobby: (_: {
     conversationId: string;
     isVideoCall: boolean;
   }) => void;
-}
+};
 
 type PropsHousekeeping = {
   i18n: LocalizerType;

ts/components/conversation/ContactDetail.tsx

@@ -21,12 +21,12 @@ import {
 
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   contact: ContactType;
   hasSignalAccount: boolean;
   i18n: LocalizerType;
   onSendMessage: () => void;
-}
+};
 
 function getLabelForEmail(method: Email, i18n: LocalizerType): string {
   switch (method.type) {

ts/components/conversation/ContactName.tsx

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
@@ -6,14 +6,14 @@ import React from 'react';
 import { LocalizerType } from '../../types/Util';
 import { Emojify } from './Emojify';
 
-export interface PropsType {
+export type PropsType = {
   i18n: LocalizerType;
   title: string;
   module?: string;
   name?: string;
   phoneNumber?: string;
   profileName?: string;
-}
+};
 
 export const ContactName = ({ module, title }: PropsType): JSX.Element => {
   const prefix = module || 'module-contact-name';

ts/components/conversation/ConversationHeader.tsx

@@ -32,7 +32,7 @@ export enum OutgoingCallButtonStyle {
   Join,
 }
 
-export interface PropsDataType {
+export type PropsDataType = {
   id: string;
   name?: string;
 
@@ -58,9 +58,9 @@ export interface PropsDataType {
 
   showBackButton?: boolean;
   outgoingCallButtonStyle: OutgoingCallButtonStyle;
-}
+};
 
-export interface PropsActionsType {
+export type PropsActionsType = {
   onSetMuteNotifications: (seconds: number) => void;
   onSetDisappearingMessages: (seconds: number) => void;
   onDeleteMessages: () => void;
@@ -78,11 +78,11 @@ export interface PropsActionsType {
   onArchive: () => void;
   onMarkUnread: () => void;
   onMoveToInbox: () => void;
-}
+};
 
-export interface PropsHousekeepingType {
+export type PropsHousekeepingType = {
   i18n: LocalizerType;
-}
+};
 
 export type PropsType = PropsDataType &
   PropsActionsType &

ts/components/conversation/EmbeddedContact.tsx

@@ -13,7 +13,7 @@ import {
   renderName,
 } from './_contactUtil';
 
-export interface Props {
+export type Props = {
   contact: ContactType;
   i18n: LocalizerType;
   isIncoming: boolean;
@@ -21,7 +21,7 @@ export interface Props {
   withContentBelow: boolean;
   tabIndex: number;
   onClick?: () => void;
-}
+};
 
 export class EmbeddedContact extends React.Component<Props> {
   public render(): JSX.Element {

ts/components/conversation/Emojify.tsx

@@ -40,13 +40,13 @@ function getImageTag({
   );
 }
 
-export interface Props {
+export type Props = {
   text: string;
   /** A class name to be added to the generated emoji images */
   sizeClass?: SizeClassType;
   /** Allows you to customize now non-newlines are rendered. Simplest is just a <span>. */
   renderNonEmoji?: RenderTextCallbackType;
-}
+};
 
 export class Emojify extends React.Component<Props> {
   public static defaultProps: Partial<Props> = {

ts/components/conversation/ExpireTimer.tsx

@@ -6,14 +6,14 @@ import classNames from 'classnames';
 
 import { getIncrement, getTimerBucket } from '../../util/timer';
 
-export interface Props {
+export type Props = {
   withImageNoCaption?: boolean;
   withSticker?: boolean;
   withTapToViewExpired?: boolean;
   expirationLength: number;
   expirationTimestamp: number;
   direction?: 'incoming' | 'outgoing';
-}
+};
 
 export class ExpireTimer extends React.Component<Props> {
   private interval: NodeJS.Timeout | null;

ts/components/conversation/GroupNotification.tsx

@@ -10,21 +10,21 @@ import { LocalizerType } from '../../types/Util';
 
 import { missingCaseError } from '../../util/missingCaseError';
 
-interface Contact {
+type Contact = {
   phoneNumber?: string;
   profileName?: string;
   name?: string;
   title: string;
   isMe?: boolean;
-}
+};
 
 export type ChangeType = 'add' | 'remove' | 'name' | 'avatar' | 'general';
 
-interface Change {
+type Change = {
   type: ChangeType;
   newName?: string;
   contacts?: Array<Contact>;
-}
+};
 
 export type PropsData = {
   from: Contact;

ts/components/conversation/Image.tsx

@@ -9,7 +9,7 @@ import { Spinner } from '../Spinner';
 import { LocalizerType } from '../../types/Util';
 import { AttachmentType } from '../../types/Attachment';
 
-export interface Props {
+export type Props = {
   alt: string;
   attachment: AttachmentType;
   url: string;
@@ -40,7 +40,7 @@ export interface Props {
   onClick?: (attachment: AttachmentType) => void;
   onClickClose?: (attachment: AttachmentType) => void;
   onError?: () => void;
-}
+};
 
 export class Image extends React.Component<Props> {
   private canClick() {

ts/components/conversation/ImageGrid.tsx

@@ -18,7 +18,7 @@ import { Image } from './Image';
 
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   attachments: Array<AttachmentType>;
   withContentAbove?: boolean;
   withContentBelow?: boolean;
@@ -31,7 +31,7 @@ export interface Props {
 
   onError: () => void;
   onClick?: (attachment: AttachmentType) => void;
-}
+};
 
 export const ImageGrid = ({
   attachments,

ts/components/conversation/LinkPreviewDate.tsx

@@ -5,10 +5,10 @@ import * as React from 'react';
 import moment, { Moment } from 'moment';
 import { isLinkPreviewDateValid } from '../../linkPreviews/isLinkPreviewDateValid';
 
-interface Props {
+type Props = {
   date: null | number;
   className?: string;
-}
+};
 
 export const LinkPreviewDate: React.FC<Props> = ({
   date,

ts/components/conversation/Linkify.tsx

@@ -36,11 +36,11 @@ const linkify = LinkifyIt()
     'travel',
   ]);
 
-export interface Props {
+export type Props = {
   text: string;
   /** Allows you to customize now non-links are rendered. Simplest is just a <span>. */
   renderNonLink?: RenderTextCallbackType;
-}
+};
 
 const SUPPORTED_PROTOCOLS = /^(http|https):/i;
 

ts/components/conversation/Message.tsx

@@ -52,9 +52,9 @@ import { createRefMerger } from '../_util';
 import { emojiToData } from '../emoji/lib';
 import { SmartReactionPicker } from '../../state/smart/ReactionPicker';
 
-interface Trigger {
+type Trigger = {
   handleContextClick: (event: React.MouseEvent<HTMLDivElement>) => void;
-}
+};
 
 const STICKER_SIZE = 200;
 const SELECTED_TIMEOUT = 1000;
@@ -190,7 +190,7 @@ export type Props = PropsData &
   PropsActions &
   Pick<ReactionPickerProps, 'renderEmojiPicker'>;
 
-interface State {
+type State = {
   expiring: boolean;
   expired: boolean;
   imageBroken: boolean;
@@ -205,7 +205,7 @@ interface State {
 
   containerWidth: number;
   canDeleteForEveryone: boolean;
-}
+};
 
 const EXPIRATION_CHECK_MINIMUM = 2000;
 const EXPIRED_DELAY = 600;

ts/components/conversation/MessageBody.tsx

@@ -20,7 +20,7 @@ type OpenConversationActionType = (
   messageId?: string
 ) => void;
 
-export interface Props {
+export type Props = {
   direction?: 'incoming' | 'outgoing';
   text: string;
   textPending?: boolean;
@@ -31,7 +31,7 @@ export interface Props {
   i18n: LocalizerType;
   bodyRanges?: BodyRangesType;
   openConversation?: OpenConversationActionType;
-}
+};
 
 const renderEmoji = ({
   text,

ts/components/conversation/MessageDetail.tsx

@@ -11,7 +11,7 @@ import { Message, MessageStatusType, Props as MessageProps } from './Message';
 import { LocalizerType } from '../../types/Util';
 import { ColorType } from '../../types/Colors';
 
-interface Contact {
+type Contact = {
   status: MessageStatusType;
 
   title: string;
@@ -27,9 +27,9 @@ interface Contact {
 
   onSendAnyway: () => void;
   onShowSafetyNumber: () => void;
-}
+};
 
-export interface Props {
+export type Props = {
   sentAt: number;
   receivedAt: number;
 
@@ -38,7 +38,7 @@ export interface Props {
   contacts: Array<Contact>;
 
   i18n: LocalizerType;
-}
+};
 
 const _keyForError = (error: Error): string => {
   return `${error.name}-${error.message}`;

ts/components/conversation/ProfileChangeNotification.tsx

@@ -11,11 +11,11 @@ import {
   ProfileNameChangeType,
 } from '../../util/getStringForProfileChange';
 
-export interface PropsType {
+export type PropsType = {
   change: ProfileNameChangeType;
   changedContact: ConversationType;
   i18n: LocalizerType;
-}
+};
 
 export function ProfileChangeNotification(props: PropsType): JSX.Element {
   const { change, changedContact, i18n } = props;

ts/components/conversation/Quote.tsx

@@ -13,7 +13,7 @@ import { ColorType } from '../../types/Colors';
 import { ContactName } from './ContactName';
 import { getTextWithMentions } from '../../util/getTextWithMentions';
 
-export interface Props {
+export type Props = {
   attachment?: QuotedAttachmentType;
   authorTitle: string;
   authorPhoneNumber?: string;
@@ -29,25 +29,25 @@ export interface Props {
   onClose?: () => void;
   text: string;
   referencedMessageNotFound: boolean;
-}
+};
 
-interface State {
+type State = {
   imageBroken: boolean;
-}
+};
 
-export interface QuotedAttachmentType {
+export type QuotedAttachmentType = {
   contentType: MIME.MIMEType;
   fileName: string;
   /** Not included in protobuf */
   isVoiceMessage: boolean;
   thumbnail?: Attachment;
-}
+};
 
-interface Attachment {
+type Attachment = {
   contentType: MIME.MIMEType;
   /** Not included in protobuf, and is loaded asynchronously */
   objectUrl?: string;
-}
+};
 
 function validateQuote(quote: Props): boolean {
   if (quote.text) {

ts/components/conversation/ReactionViewer.tsx

@@ -46,12 +46,12 @@ const DEFAULT_EMOJI_ORDER = [
   'rage',
 ];
 
-interface ReactionCategory {
+type ReactionCategory = {
   count: number;
   emoji?: string;
   id: string;
   index: number;
-}
+};
 
 type ReactionWithEmojiData = Reaction & EmojiData;
 

ts/components/conversation/ResetSessionNotification.tsx

@@ -5,9 +5,9 @@ import React from 'react';
 
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   i18n: LocalizerType;
-}
+};
 
 export const ResetSessionNotification = ({ i18n }: Props): JSX.Element => (
   <div className="module-reset-session-notification">

ts/components/conversation/SafetyNumberNotification.tsx

@@ -7,13 +7,13 @@ import { ContactName } from './ContactName';
 import { Intl } from '../Intl';
 import { LocalizerType } from '../../types/Util';
 
-export interface ContactType {
+export type ContactType = {
   id: string;
   phoneNumber?: string;
   profileName?: string;
   title: string;
   name?: string;
-}
+};
 
 export type PropsData = {
   isGroup: boolean;

ts/components/conversation/StagedGenericAttachment.tsx

@@ -6,11 +6,11 @@ import React from 'react';
 import { AttachmentType, getExtensionForDisplay } from '../../types/Attachment';
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   attachment: AttachmentType;
   onClose: (attachment: AttachmentType) => void;
   i18n: LocalizerType;
-}
+};
 
 export const StagedGenericAttachment = ({
   attachment,

ts/components/conversation/StagedLinkPreview.tsx

@@ -10,7 +10,7 @@ import { LinkPreviewDate } from './LinkPreviewDate';
 import { AttachmentType, isImageAttachment } from '../../types/Attachment';
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   isLoaded: boolean;
   title: string;
   description: null | string;
@@ -20,7 +20,7 @@ export interface Props {
 
   i18n: LocalizerType;
   onClose?: () => void;
-}
+};
 
 export const StagedLinkPreview: React.FC<Props> = ({
   isLoaded,

ts/components/conversation/StagedPlaceholderAttachment.tsx

@@ -1,13 +1,13 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
 import { LocalizerType } from '../../types/Util';
 
-interface Props {
+type Props = {
   onClick: () => void;
   i18n: LocalizerType;
-}
+};
 
 export const StagedPlaceholderAttachment = ({
   i18n,

ts/components/conversation/Timestamp.tsx

@@ -9,7 +9,7 @@ import { formatRelativeTime } from '../../util/formatRelativeTime';
 
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   timestamp?: number;
   extended?: boolean;
   module?: string;
@@ -19,7 +19,7 @@ export interface Props {
   withUnread?: boolean;
   direction?: 'incoming' | 'outgoing';
   i18n: LocalizerType;
-}
+};
 
 const UPDATE_FREQUENCY = 60 * 1000;
 

ts/components/conversation/TypingAnimation.tsx

@@ -6,10 +6,10 @@ import classNames from 'classnames';
 
 import { LocalizerType } from '../../types/Util';
 
-export interface Props {
+export type Props = {
   i18n: LocalizerType;
   color?: string;
-}
+};
 
 export const TypingAnimation = ({ i18n, color }: Props): JSX.Element => (
   <div className="module-typing-animation" title={i18n('typingAlt')}>

ts/components/conversation/TypingBubble.tsx

@@ -10,7 +10,7 @@ import { Avatar } from '../Avatar';
 import { LocalizerType } from '../../types/Util';
 import { ColorType } from '../../types/Colors';
 
-export interface Props {
+export type Props = {
   avatarPath?: string;
   color: ColorType;
   name?: string;
@@ -19,7 +19,7 @@ export interface Props {
   title: string;
   conversationType: 'group' | 'direct';
   i18n: LocalizerType;
-}
+};
 
 export class TypingBubble extends React.PureComponent<Props> {
   public renderAvatar(): JSX.Element | null {

ts/components/conversation/UnsupportedMessage.tsx

@@ -8,14 +8,14 @@ import { ContactName } from './ContactName';
 import { Intl } from '../Intl';
 import { LocalizerType } from '../../types/Util';
 
-export interface ContactType {
+export type ContactType = {
   id: string;
   phoneNumber?: string;
   profileName?: string;
   title: string;
   name?: string;
   isMe: boolean;
-}
+};
 
 export type PropsData = {
   canProcessNow: boolean;

ts/components/conversation/VerificationNotification.tsx

@@ -10,12 +10,12 @@ import { LocalizerType } from '../../types/Util';
 
 import { missingCaseError } from '../../util/missingCaseError';
 
-interface Contact {
+type Contact = {
   phoneNumber?: string;
   profileName?: string;
   name?: string;
   title: string;
-}
+};
 
 export type PropsData = {
   type: 'markVerified' | 'markNotVerified';

ts/components/conversation/media-gallery/AttachmentSection.tsx

@@ -10,13 +10,13 @@ import { MediaItemType } from '../../LightboxGallery';
 import { missingCaseError } from '../../../util/missingCaseError';
 import { LocalizerType } from '../../../types/Util';
 
-export interface Props {
+export type Props = {
   i18n: LocalizerType;
   header?: string;
   type: 'media' | 'documents';
   mediaItems: Array<MediaItemType>;
   onItemClick?: (event: ItemClickEvent) => void;
-}
+};
 
 export class AttachmentSection extends React.Component<Props> {
   public render(): JSX.Element {

ts/components/conversation/media-gallery/DocumentListItem.tsx

@@ -7,7 +7,7 @@ import classNames from 'classnames';
 import moment from 'moment';
 import formatFileSize from 'filesize';
 
-interface Props {
+type Props = {
   // Required
   timestamp: number;
 
@@ -16,7 +16,7 @@ interface Props {
   fileSize?: number;
   onClick?: () => void;
   shouldShowSeparator?: boolean;
-}
+};
 
 export class DocumentListItem extends React.Component<Props> {
   public static defaultProps: Partial<Props> = {

ts/components/conversation/media-gallery/EmptyState.tsx

@@ -3,9 +3,9 @@
 
 import React from 'react';
 
-interface Props {
+type Props = {
   label: string;
-}
+};
 
 export const EmptyState = ({ label }: Props): JSX.Element => (
   <div className="module-empty-state">{label}</div>

ts/components/conversation/media-gallery/MediaGallery.tsx

@@ -15,23 +15,23 @@ import { LocalizerType } from '../../../types/Util';
 
 import { MediaItemType } from '../../LightboxGallery';
 
-export interface Props {
+export type Props = {
   documents: Array<MediaItemType>;
   i18n: LocalizerType;
   media: Array<MediaItemType>;
 
   onItemClick?: (event: ItemClickEvent) => void;
-}
+};
 
-interface State {
+type State = {
   selectedTab: 'media' | 'documents';
-}
+};
 
 const MONTH_FORMAT = 'MMMM YYYY';
 
-interface TabSelectEvent {
+type TabSelectEvent = {
   type: 'media' | 'documents';
-}
+};
 
 const Tab = ({
   isSelected,

ts/components/conversation/media-gallery/MediaGridItem.tsx

@@ -11,15 +11,15 @@ import {
 import { LocalizerType } from '../../../types/Util';
 import { MediaItemType } from '../../LightboxGallery';
 
-export interface Props {
+export type Props = {
   mediaItem: MediaItemType;
   onClick?: () => void;
   i18n: LocalizerType;
-}
+};
 
-interface State {
+type State = {
   imageBroken: boolean;
-}
+};
 
 export class MediaGridItem extends React.Component<Props, State> {
   private readonly onImageErrorBound: () => void;

ts/components/conversation/media-gallery/groupMediaItemsByDate.ts

@@ -11,10 +11,10 @@ import { MediaItemType } from '../../LightboxGallery';
 type StaticSectionType = 'today' | 'yesterday' | 'thisWeek' | 'thisMonth';
 type YearMonthSectionType = 'yearMonth';
 
-interface GenericSection<T> {
+type GenericSection<T> = {
   type: T;
   mediaItems: Array<MediaItemType>;
-}
+};
 type StaticSection = GenericSection<StaticSectionType>;
 type YearMonthSection = GenericSection<YearMonthSectionType> & {
   year: number;
@@ -93,11 +93,11 @@ const toSection = (
   }
 };
 
-interface GenericMediaItemWithSection<T> {
+type GenericMediaItemWithSection<T> = {
   order: number;
   type: T;
   mediaItem: MediaItemType;
-}
+};
 type MediaItemWithStaticSection = GenericMediaItemWithSection<
   StaticSectionType
 >;

ts/components/conversation/media-gallery/types/ItemClickEvent.ts

@@ -1,11 +1,11 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { AttachmentType } from '../../../../types/Attachment';
 import { Message } from './Message';
 
-export interface ItemClickEvent {
+export type ItemClickEvent = {
   message: Message;
   attachment: AttachmentType;
   type: 'media' | 'documents';
-}
+};

ts/linkPreviews/linkPreviewFetch.ts

@@ -54,17 +54,17 @@ const emptyContentType = { type: null, charset: null };
 
 type FetchFn = (href: string, init: RequestInit) => Promise<Response>;
 
-export interface LinkPreviewMetadata {
+export type LinkPreviewMetadata = {
   title: string;
   description: null | string;
   date: null | number;
   imageHref: null | string;
-}
+};
 
-export interface LinkPreviewImage {
+export type LinkPreviewImage = {
   data: ArrayBuffer;
   contentType: MIMEType;
-}
+};
 
 type ParsedContentType =
   | { type: null; charset: null }

ts/model-types.d.ts

@@ -41,10 +41,10 @@ export declare class DeletesModelType extends Backbone.Model<
 
 type TaskResultType = any;
 
-export interface CustomError extends Error {
+export type CustomError = Error & {
   identifier?: string;
   number?: string;
-}
+};
 
 export type GroupMigrationType = {
   areWeInvited: boolean;

ts/models/conversations.ts

@@ -76,10 +76,10 @@ const COLORS = [
 
 const THREE_HOURS = 3 * 60 * 60 * 1000;
 
-interface CustomError extends Error {
+type CustomError = Error & {
   identifier?: string;
   number?: string;
-}
+};
 
 export class ConversationModel extends window.Backbone.Model<
   ConversationAttributesType
@@ -4556,9 +4556,9 @@ window.Whisper.GroupMemberConversation = window.Backbone.Model.extend({
   },
 });
 
-interface SortableByTitle {
+type SortableByTitle = {
   getTitle: () => string;
-}
+};
 
 const sortConversationTitles = (
   left: SortableByTitle,

ts/notifications/getStatus.ts

@@ -1,20 +1,20 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-interface Environment {
+type Environment = {
   isAppFocused: boolean;
   isAudioNotificationEnabled: boolean;
   isEnabled: boolean;
   hasNotifications: boolean;
   userSetting: UserSetting;
-}
+};
 
-interface Status {
+type Status = {
   shouldClearNotifications: boolean;
   shouldPlayNotificationSound: boolean;
   shouldShowNotifications: boolean;
   type: Type;
-}
+};
 
 type UserSetting = 'off' | 'count' | 'name' | 'message';
 

ts/quill/emoji/completion.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import Quill from 'quill';
@@ -22,11 +22,11 @@ import { getBlotTextPartitions, matchBlotTextPartitions } from '../util';
 
 const Keyboard = Quill.import('modules/keyboard');
 
-interface EmojiPickerOptions {
+type EmojiPickerOptions = {
   onPickEmoji: (emoji: EmojiPickDataType) => void;
   setEmojiPickerElement: (element: JSX.Element | null) => void;
   skinTone: number;
-}
+};
 
 export class EmojiCompletion {
   results: Array<EmojiData>;

ts/quill/mentions/completion.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import _ from 'lodash';
@@ -15,14 +15,16 @@ import { LocalizerType } from '../../types/Util';
 import { MemberRepository } from '../memberRepository';
 import { matchBlotTextPartitions } from '../util';
 
-export interface MentionCompletionOptions {
+export type MentionCompletionOptions = {
   i18n: LocalizerType;
   memberRepositoryRef: RefObject<MemberRepository>;
   setMentionPickerElement: (element: JSX.Element | null) => void;
   me?: ConversationType;
-}
+};
 
 declare global {
+  // We want to extend `HTMLElement`'s properties, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface HTMLElement {
     // Webkit-specific
     scrollIntoViewIfNeeded: (bringToCenter: boolean) => void;

ts/quill/types.d.ts

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import UpdatedDelta from 'quill-delta';
@@ -11,6 +11,8 @@ declare module 'react-quill' {
   type DeltaStatic = UpdatedDelta;
 }
 
+// We want to extend some existing interfaces.
+/* eslint-disable no-restricted-syntax */
 declare module 'quill' {
   // this type is fixed in @types/quill, but our version of react-quill cannot
   // use the version of quill that has this fix in its typings
@@ -76,3 +78,4 @@ declare module 'quill' {
     bindings: Record<string | number, Array<unknown>>;
   }
 }
+/* eslint-enable no-restricted-syntax */

ts/quill/util.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import emojiRegex from 'emoji-regex';
@@ -9,10 +9,10 @@ import Op from 'quill-delta/dist/Op';
 import { BodyRangeType } from '../types/Util';
 import { MentionBlot } from './mentions/blot';
 
-export interface MentionBlotValue {
+export type MentionBlotValue = {
   uuid: string;
   title: string;
-}
+};
 
 export const isMentionBlot = (blot: LeafBlot): blot is MentionBlot =>
   blot.value() && blot.value().mention;

ts/sql/Interface.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable @typescript-eslint/ban-types */
@@ -30,7 +30,7 @@ export type StickerPackType = any;
 export type StickerType = any;
 export type UnprocessedType = any;
 
-export interface DataInterface {
+export type DataInterface = {
   close: () => Promise<void>;
   removeDB: () => Promise<void>;
   removeIndexedDBFiles: () => Promise<void>;
@@ -188,7 +188,7 @@ export interface DataInterface {
     conversationId: string,
     options: { limit: number }
   ) => Promise<Array<MessageType>>;
-}
+};
 
 // The reason for client/server divergence is the need to inject Backbone models and
 //   collections into data calls so those are the objects returned. This was necessary in

ts/sql/Server.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable no-nested-ternary */
@@ -56,6 +56,8 @@ import {
 } from './Interface';
 
 declare global {
+  // We want to extend `Function`'s properties, so we need to use an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Function {
     needsSerial?: boolean;
   }

ts/sqlcipher.d.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 // Taken from:
@@ -35,10 +35,10 @@ declare module '@journeyapps/sqlcipher' {
     ): Database;
   };
 
-  export interface RunResult extends Statement {
+  export type RunResult = Statement & {
     lastID: number;
     changes: number;
-  }
+  };
 
   export class Statement {
     bind(callback?: (err: Error | null) => void): this;

ts/state/createStore.ts

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable no-console */
@@ -17,7 +17,8 @@ import { createLogger } from 'redux-logger';
 import { reducer, StateType } from './reducer';
 
 declare global {
-  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  // We want to extend `window`'s properties, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax, @typescript-eslint/no-unused-vars
   interface Console {
     _log: Console['log'];
   }

ts/state/ducks/calling.ts

@@ -30,24 +30,24 @@ import { LatestQueue } from '../../util/LatestQueue';
 
 // State
 
-export interface GroupCallPeekInfoType {
+export type GroupCallPeekInfoType = {
   uuids: Array<string>;
   creatorUuid?: string;
   eraId?: string;
   maxDevices: number;
   deviceCount: number;
-}
+};
 
-export interface GroupCallParticipantInfoType {
+export type GroupCallParticipantInfoType = {
   uuid: string;
   demuxId: number;
   hasRemoteAudio: boolean;
   hasRemoteVideo: boolean;
   speakerTime?: number;
   videoAspectRatio: number;
-}
+};
 
-export interface DirectCallStateType {
+export type DirectCallStateType = {
   callMode: CallMode.Direct;
   conversationId: string;
   callState?: CallState;
@@ -55,18 +55,18 @@ export interface DirectCallStateType {
   isIncoming: boolean;
   isVideoCall: boolean;
   hasRemoteVideo?: boolean;
-}
+};
 
-export interface GroupCallStateType {
+export type GroupCallStateType = {
   callMode: CallMode.Group;
   conversationId: string;
   connectionState: GroupCallConnectionState;
   joinState: GroupCallJoinState;
   peekInfo: GroupCallPeekInfoType;
   remoteParticipants: Array<GroupCallParticipantInfoType>;
-}
+};
 
-export interface ActiveCallStateType {
+export type ActiveCallStateType = {
   conversationId: string;
   hasLocalAudio: boolean;
   hasLocalVideo: boolean;
@@ -76,11 +76,11 @@ export interface ActiveCallStateType {
   safetyNumberChangedUuids: Array<string>;
   settingsDialogOpen: boolean;
   showParticipantsList: boolean;
-}
+};
 
-export interface CallsByConversationType {
+export type CallsByConversationType = {
   [conversationId: string]: DirectCallStateType | GroupCallStateType;
-}
+};
 
 export type CallingStateType = MediaDeviceSettings & {
   callsByConversation: CallsByConversationType;
@@ -145,15 +145,15 @@ type PeekNotConnectedGroupCallType = {
   conversationId: string;
 };
 
-interface StartDirectCallType {
+type StartDirectCallType = {
   conversationId: string;
   hasLocalAudio: boolean;
   hasLocalVideo: boolean;
-}
+};
 
-export interface StartCallType extends StartDirectCallType {
+export type StartCallType = StartDirectCallType & {
   callMode: CallMode.Direct | CallMode.Group;
-}
+};
 
 export type RemoteVideoChangeType = {
   conversationId: string;

ts/state/smart/ConversationHeader.tsx

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { connect } from 'react-redux';
@@ -20,7 +20,7 @@ import { getOwn } from '../../util/getOwn';
 import { missingCaseError } from '../../util/missingCaseError';
 import { isGroupCallingEnabled } from '../../util/isGroupCallingEnabled';
 
-export interface OwnProps {
+export type OwnProps = {
   id: string;
 
   onDeleteMessages: () => void;
@@ -39,7 +39,7 @@ export interface OwnProps {
   onMarkUnread: () => void;
   onMoveToInbox: () => void;
   onShowSafetyNumber: () => void;
-}
+};
 
 const getOutgoingCallButtonStyle = (
   conversation: ConversationType,

ts/test-both/util/assignWithNoUnnecessaryAllocation_test.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { assert } from 'chai';
@@ -6,10 +6,10 @@ import { assert } from 'chai';
 import { assignWithNoUnnecessaryAllocation } from '../../util/assignWithNoUnnecessaryAllocation';
 
 describe('assignWithNoUnnecessaryAllocation', () => {
-  interface Person {
+  type Person = {
     name?: string;
     age?: number;
-  }
+  };
 
   it('returns the same object if there are no modifications', () => {
     const empty = {};

ts/test-node/quill/mentions/matchers_test.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { assert } from 'chai';
@@ -69,14 +69,14 @@ const memberRepositoryRef: RefObject<MemberRepository> = {
 
 const matcher = matchMention(memberRepositoryRef);
 
-interface Mention {
+type Mention = {
   uuid: string;
   title: string;
-}
+};
 
-interface MentionInsert {
+type MentionInsert = {
   mention: Mention;
-}
+};
 
 const isMention = (insert?: unknown): insert is MentionInsert => {
   if (insert) {

ts/textsecure/Crypto.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
@@ -9,6 +9,8 @@ import { ByteBufferClass } from '../window.d';
 declare global {
   // this is fixed in already, and won't be necessary when the new definitions
   // files are used: https://github.com/microsoft/TSJS-lib-generator/pull/843
+  // We want to extend `SubtleCrypto`, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   export interface SubtleCrypto {
     decrypt(
       algorithm:
@@ -108,10 +110,10 @@ const PROFILE_KEY_LENGTH = 32; // bytes
 const PROFILE_TAG_LENGTH = 128; // bits
 const PROFILE_NAME_PADDED_LENGTH = 53; // bytes
 
-interface EncryptedAttachment {
+type EncryptedAttachment = {
   ciphertext: ArrayBuffer;
   digest: ArrayBuffer;
-}
+};
 
 async function verifyDigest(
   data: ArrayBuffer,

ts/textsecure/MessageReceiver.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable @typescript-eslint/ban-types */
@@ -49,6 +49,8 @@ const GROUPV2_ID_LENGTH = 32;
 const RETRY_TIMEOUT = 2 * 60 * 1000;
 
 declare global {
+  // We want to extend `Event`, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Event {
     code?: string | number;
     configuration?: any;
@@ -79,6 +81,8 @@ declare global {
     typing?: any;
     verified?: any;
   }
+  // We want to extend `Error`, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Error {
     reason?: any;
     stackForLog?: string;

ts/textsecure/SendMessage.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable no-nested-ternary */
@@ -70,10 +70,10 @@ export type SendOptionsType = {
   online?: boolean;
 };
 
-export interface CustomError extends Error {
+export type CustomError = Error & {
   identifier?: string;
   number?: string;
-}
+};
 
 export type CallbackResultType = {
   successfulIdentifiers?: Array<any>;
@@ -105,9 +105,9 @@ type GroupV1InfoType = {
   members: Array<string>;
 };
 
-interface GroupCallUpdateType {
+type GroupCallUpdateType = {
   eraId: string;
-}
+};
 
 type MessageOptionsType = {
   attachments?: Array<AttachmentType> | null;

ts/textsecure/Storage.ts

@@ -1,11 +1,11 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import utils from './Helpers';
 
 // Default implmentation working with localStorage
-const localStorageImpl = {
+const localStorageImpl: StorageInterface = {
   put(key: string, value: any) {
     if (value === undefined) {
       throw new Error('Tried to store undefined');
@@ -26,14 +26,14 @@ const localStorageImpl = {
   },
 };
 
-export interface StorageInterface {
+export type StorageInterface = {
   put(key: string, value: any): void | Promise<void>;
   get(key: string, defaultValue: any): any;
   remove(key: string): void | Promise<void>;
-}
+};
 
 const Storage = {
-  impl: localStorageImpl as StorageInterface,
+  impl: localStorageImpl,
 
   put(key: string, value: unknown): Promise<void> | void {
     return Storage.impl.put(key, value);

ts/textsecure/WebAPI.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 /* eslint-disable no-param-reassign */
@@ -586,6 +586,8 @@ async function _outerAjax(url: string | null, options: PromiseAjaxOptionsType) {
 }
 
 declare global {
+  // We want to extend `Error`, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Error {
     code?: number | string;
     response?: any;

ts/types/Attachment.ts

@@ -1,4 +1,4 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import is from '@sindresorhus/is';
@@ -20,7 +20,7 @@ const MIN_HEIGHT = 50;
 
 // Used for display
 
-export interface AttachmentType {
+export type AttachmentType = {
   blurHash?: string;
   caption?: string;
   contentType: MIME.MIMEType;
@@ -47,7 +47,7 @@ export interface AttachmentType {
     url: string;
     contentType: MIME.MIMEType;
   };
-}
+};
 
 // UI-focused functions
 
@@ -288,9 +288,9 @@ export type Attachment = {
   // digest?: ArrayBuffer;
 } & Partial<AttachmentSchemaVersion3>;
 
-interface AttachmentSchemaVersion3 {
+type AttachmentSchemaVersion3 = {
   path: string;
-}
+};
 
 export const isVisualMedia = (attachment: Attachment): boolean => {
   const { contentType } = attachment;

ts/types/Calling.ts

@@ -10,7 +10,7 @@ export enum CallMode {
   Group = 'Group',
 }
 
-interface ActiveCallBaseType {
+type ActiveCallBaseType = {
   conversation: ConversationType;
   hasLocalAudio: boolean;
   hasLocalVideo: boolean;
@@ -20,9 +20,9 @@ interface ActiveCallBaseType {
   settingsDialogOpen: boolean;
   showParticipantsList: boolean;
   showSafetyNumberDialog?: boolean;
-}
+};
 
-interface ActiveDirectCallType extends ActiveCallBaseType {
+type ActiveDirectCallType = ActiveCallBaseType & {
   callMode: CallMode.Direct;
   callState?: CallState;
   callEndedReason?: CallEndedReason;
@@ -32,9 +32,9 @@ interface ActiveDirectCallType extends ActiveCallBaseType {
       hasRemoteVideo: boolean;
     }
   ];
-}
+};
 
-interface ActiveGroupCallType extends ActiveCallBaseType {
+type ActiveGroupCallType = ActiveCallBaseType & {
   callMode: CallMode.Group;
   connectionState: GroupCallConnectionState;
   conversationsWithSafetyNumberChanges: Array<ConversationType>;
@@ -43,7 +43,7 @@ interface ActiveGroupCallType extends ActiveCallBaseType {
   deviceCount: number;
   peekedParticipants: Array<ConversationType>;
   remoteParticipants: Array<GroupCallRemoteParticipantType>;
-}
+};
 
 export type ActiveCallType = ActiveDirectCallType | ActiveGroupCallType;
 
@@ -96,28 +96,28 @@ export enum GroupCallJoinState {
   Joined = 2,
 }
 
-export interface GroupCallRemoteParticipantType extends ConversationType {
+export type GroupCallRemoteParticipantType = ConversationType & {
   demuxId: number;
   hasRemoteAudio: boolean;
   hasRemoteVideo: boolean;
   speakerTime?: number;
   videoAspectRatio: number;
-}
+};
 
 // Similar to RingRTC's `VideoRequest` but without the `framerate` property.
-export interface GroupCallVideoRequest {
+export type GroupCallVideoRequest = {
   demuxId: number;
   width: number;
   height: number;
-}
+};
 
 // Should match RingRTC's VideoFrameSource
-export interface VideoFrameSource {
+export type VideoFrameSource = {
   receiveVideoFrame(buffer: ArrayBuffer): [number, number] | undefined;
-}
+};
 
 // Must be kept in sync with RingRTC.AudioDevice
-export interface AudioDevice {
+export type AudioDevice = {
   // Device name.
   name: string;
   // Index of this device, starting from 0.
@@ -126,7 +126,7 @@ export interface AudioDevice {
   uniqueId: string;
   // If present, the identifier of a localized string to substitute for the device name.
   i18nKey?: string;
-}
+};
 
 export enum CallingDeviceType {
   CAMERA,
@@ -143,21 +143,21 @@ export type MediaDeviceSettings = {
   selectedCamera: string | undefined;
 };
 
-interface DirectCallHistoryDetailsType {
+type DirectCallHistoryDetailsType = {
   callMode: CallMode.Direct;
   wasIncoming: boolean;
   wasVideoCall: boolean;
   wasDeclined: boolean;
   acceptedTime?: number;
   endedTime: number;
-}
+};
 
-interface GroupCallHistoryDetailsType {
+type GroupCallHistoryDetailsType = {
   callMode: CallMode.Group;
   creatorUuid: string;
   eraId: string;
   startedTime: number;
-}
+};
 
 export type CallHistoryDetailsType =
   | DirectCallHistoryDetailsType

ts/types/Contact.tsx

@@ -1,9 +1,9 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { format as formatPhoneNumber } from './PhoneNumber';
 
-export interface ContactType {
+export type ContactType = {
   name?: Name;
   number?: Array<Phone>;
   email?: Array<Email>;
@@ -11,16 +11,16 @@ export interface ContactType {
   avatar?: Avatar;
   organization?: string;
   signalAccount?: string;
-}
+};
 
-interface Name {
+type Name = {
   givenName?: string;
   familyName?: string;
   prefix?: string;
   suffix?: string;
   middleName?: string;
   displayName?: string;
-}
+};
 
 export enum ContactFormType {
   HOME = 1,
@@ -35,19 +35,19 @@ export enum AddressType {
   CUSTOM = 3,
 }
 
-export interface Phone {
+export type Phone = {
   value: string;
   type: ContactFormType;
   label?: string;
-}
+};
 
-export interface Email {
+export type Email = {
   value: string;
   type: ContactFormType;
   label?: string;
-}
+};
 
-export interface PostalAddress {
+export type PostalAddress = {
   type: AddressType;
   label?: string;
   street?: string;
@@ -57,18 +57,18 @@ export interface PostalAddress {
   region?: string;
   postcode?: string;
   country?: string;
-}
+};
 
-interface Avatar {
+type Avatar = {
   avatar: Attachment;
   isProfile: boolean;
-}
+};
 
-interface Attachment {
+type Attachment = {
   path?: string;
   error?: boolean;
   pending?: boolean;
-}
+};
 
 export function contactSelector(
   contact: ContactType,

ts/types/Util.ts

@@ -1,13 +1,13 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-export interface BodyRangeType {
+export type BodyRangeType = {
   start: number;
   length: number;
   mentionUuid: string;
   replacementText: string;
   conversationID?: string;
-}
+};
 
 export type BodyRangesType = Array<BodyRangeType>;
 

ts/types/message/LinkPreviews.ts

@@ -3,7 +3,7 @@
 
 import { AttachmentType } from '../Attachment';
 
-export interface LinkPreviewType {
+export type LinkPreviewType = {
   title: string;
   description?: string;
   domain: string;
@@ -11,4 +11,4 @@ export interface LinkPreviewType {
   isStickerPack: boolean;
   image?: AttachmentType;
   date?: number;
-}
+};

ts/util/GoogleChrome.ts

@@ -1,11 +1,9 @@
-// Copyright 2018-2020 Signal Messenger, LLC
+// Copyright 2018-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as MIME from '../types/MIME';
 
-interface MIMETypeSupportMap {
+type MIMETypeSupportMap = Record<string, boolean>;
-  [key: string]: boolean;
-}
 
 // See: https://en.wikipedia.org/wiki/Comparison_of_web_browsers#Image_format_support
 const SUPPORTED_IMAGE_MIME_TYPES: MIMETypeSupportMap = {

ts/util/batcher.ts

@@ -1,4 +1,4 @@
-// Copyright 2019-2020 Signal Messenger, LLC
+// Copyright 2019-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import PQueue from 'p-queue';
@@ -6,6 +6,8 @@ import PQueue from 'p-queue';
 import { sleep } from './sleep';
 
 declare global {
+  // We want to extend `window`'s properties, so we need an interface.
+  // eslint-disable-next-line no-restricted-syntax
   interface Window {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     batchers: Array<BatcherType<any>>;

ts/util/callingNotification.ts

@@ -1,20 +1,20 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { LocalizerType } from '../types/Util';
 import { CallMode } from '../types/Calling';
 import { missingCaseError } from './missingCaseError';
 
-interface DirectCallNotificationType {
+type DirectCallNotificationType = {
   callMode: CallMode.Direct;
   wasIncoming: boolean;
   wasVideoCall: boolean;
   wasDeclined: boolean;
   acceptedTime?: number;
   endedTime: number;
-}
+};
 
-interface GroupCallNotificationType {
+type GroupCallNotificationType = {
   activeCallConversationId?: string;
   callMode: CallMode.Group;
   conversationId: string;
@@ -27,7 +27,7 @@ interface GroupCallNotificationType {
   deviceCount: number;
   maxDevices: number;
   startedTime: number;
-}
+};
 
 export type CallingNotificationType =
   | DirectCallNotificationType

ts/util/getAnimatedPngDataIfExists.ts

@@ -1,4 +1,4 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 const PNG_SIGNATURE = new Uint8Array([137, 80, 78, 71, 13, 10, 26, 10]);
@@ -6,9 +6,9 @@ const ACTL_CHUNK_BYTES = new TextEncoder().encode('acTL');
 const IDAT_CHUNK_BYTES = new TextEncoder().encode('IDAT');
 const MAX_BYTES_TO_READ = 1024 * 1024;
 
-interface AnimatedPngData {
+type AnimatedPngData = {
   numPlays: number;
-}
+};
 
 /**
  * This is a naïve implementation. It only performs two checks: