Enable @typescript-eslint/explicit-function-return-type in /src (#9788)

* Enable `@typescript-eslint/explicit-member-accessibility` on /src

* Prettier

* Enable `@typescript-eslint/explicit-function-return-type` in /src

* Fix types

* tsc strict fixes

* Delint

* Fix test

* Fix bad merge

src/components/views/auth/AuthBody.tsx

@@ -22,6 +22,6 @@ interface Props {
     flex?: boolean;
 }
 
-export default function AuthBody({ flex, className, children }: PropsWithChildren<Props>) {
+export default function AuthBody({ flex, className, children }: PropsWithChildren<Props>): JSX.Element {
     return <main className={classNames("mx_AuthBody", className, { mx_AuthBody_flex: flex })}>{children}</main>;
 }

src/components/views/auth/CaptchaForm.tsx

@@ -49,7 +49,7 @@ export default class CaptchaForm extends React.Component<ICaptchaFormProps, ICap
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         // Just putting a script tag into the returned jsx doesn't work, annoyingly,
         // so we do this instead.
         if (this.isRecaptchaReady()) {
@@ -69,7 +69,7 @@ export default class CaptchaForm extends React.Component<ICaptchaFormProps, ICap
         }
     }
 
-    public componentWillUnmount() {
+    public componentWillUnmount(): void {
         this.resetRecaptcha();
     }
 
@@ -82,7 +82,7 @@ export default class CaptchaForm extends React.Component<ICaptchaFormProps, ICap
         );
     }
 
-    private renderRecaptcha(divId: string) {
+    private renderRecaptcha(divId: string): void {
         if (!this.isRecaptchaReady()) {
             logger.error("grecaptcha not loaded!");
             throw new Error("Recaptcha did not load successfully");
@@ -101,13 +101,13 @@ export default class CaptchaForm extends React.Component<ICaptchaFormProps, ICap
         });
     }
 
-    private resetRecaptcha() {
+    private resetRecaptcha(): void {
         if (this.captchaWidgetId) {
             global?.grecaptcha?.reset(this.captchaWidgetId);
         }
     }
 
-    private onCaptchaLoaded() {
+    private onCaptchaLoaded(): void {
         logger.log("Loaded recaptcha script.");
         try {
             this.renderRecaptcha(DIV_ID);
@@ -122,7 +122,7 @@ export default class CaptchaForm extends React.Component<ICaptchaFormProps, ICap
         }
     }
 
-    public render() {
+    public render(): JSX.Element {
         let error = null;
         if (this.state.errorText) {
             error = <div className="error">{this.state.errorText}</div>;

src/components/views/auth/EmailField.tsx

@@ -60,7 +60,7 @@ class EmailField extends PureComponent<IProps> {
         ],
     });
 
-    public onValidate = async (fieldState: IFieldState) => {
+    public onValidate = async (fieldState: IFieldState): Promise<IValidationResult> => {
         let validate = this.validate;
         if (this.props.validationRules) {
             validate = this.props.validationRules;
@@ -74,7 +74,7 @@ class EmailField extends PureComponent<IProps> {
         return result;
     };
 
-    public render() {
+    public render(): JSX.Element {
         return (
             <Field
                 id={this.props.id}

src/components/views/auth/InteractiveAuthEntryComponents.tsx

@@ -108,11 +108,11 @@ export class PasswordAuthEntry extends React.Component<IAuthEntryProps, IPasswor
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
     }
 
-    private onSubmit = (e: FormEvent) => {
+    private onSubmit = (e: FormEvent): void => {
         e.preventDefault();
         if (this.props.busy) return;
 
@@ -129,14 +129,14 @@ export class PasswordAuthEntry extends React.Component<IAuthEntryProps, IPasswor
         });
     };
 
-    private onPasswordFieldChange = (ev: ChangeEvent<HTMLInputElement>) => {
+    private onPasswordFieldChange = (ev: ChangeEvent<HTMLInputElement>): void => {
         // enable the submit button iff the password is non-empty
         this.setState({
             password: ev.target.value,
         });
     };
 
-    public render() {
+    public render(): JSX.Element {
         const passwordBoxClass = classNames({
             error: this.props.errorText,
         });
@@ -196,18 +196,18 @@ interface IRecaptchaAuthEntryProps extends IAuthEntryProps {
 export class RecaptchaAuthEntry extends React.Component<IRecaptchaAuthEntryProps> {
     public static LOGIN_TYPE = AuthType.Recaptcha;
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
     }
 
-    private onCaptchaResponse = (response: string) => {
+    private onCaptchaResponse = (response: string): void => {
         this.props.submitAuthDict({
             type: AuthType.Recaptcha,
             response: response,
         });
     };
 
-    public render() {
+    public render(): JSX.Element {
         if (this.props.busy) {
             return <Spinner />;
         }
@@ -320,11 +320,11 @@ export class TermsAuthEntry extends React.Component<ITermsAuthEntryProps, ITerms
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
     }
 
-    private togglePolicy(policyId: string) {
+    private togglePolicy(policyId: string): void {
         const newToggles = {};
         for (const policy of this.state.policies) {
             let checked = this.state.toggledPolicies[policy.id];
@@ -335,7 +335,7 @@ export class TermsAuthEntry extends React.Component<ITermsAuthEntryProps, ITerms
         this.setState({ toggledPolicies: newToggles });
     }
 
-    private trySubmit = () => {
+    private trySubmit = (): void => {
         let allChecked = true;
         for (const policy of this.state.policies) {
             const checked = this.state.toggledPolicies[policy.id];
@@ -349,7 +349,7 @@ export class TermsAuthEntry extends React.Component<ITermsAuthEntryProps, ITerms
         }
     };
 
-    public render() {
+    public render(): JSX.Element {
         if (this.props.busy) {
             return <Spinner />;
         }
@@ -434,11 +434,11 @@ export class EmailIdentityAuthEntry extends React.Component<
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
     }
 
-    public render() {
+    public render(): JSX.Element {
         let errorSection;
         // ignore the error when errcode is M_UNAUTHORIZED as we expect that error until the link is clicked.
         if (this.props.errorText && this.props.errorCode !== "M_UNAUTHORIZED") {
@@ -508,7 +508,7 @@ export class EmailIdentityAuthEntry extends React.Component<
                                                     ? () => this.setState({ requested: false })
                                                     : undefined
                                             }
-                                            onClick={async () => {
+                                            onClick={async (): Promise<void> => {
                                                 this.setState({ requesting: true });
                                                 try {
                                                     await this.props.requestEmailToken?.();
@@ -565,7 +565,7 @@ export class MsisdnAuthEntry extends React.Component<IMsisdnAuthEntryProps, IMsi
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
 
         this.setState({ requestingToken: true });
@@ -596,13 +596,13 @@ export class MsisdnAuthEntry extends React.Component<IMsisdnAuthEntryProps, IMsi
             });
     }
 
-    private onTokenChange = (e: ChangeEvent<HTMLInputElement>) => {
+    private onTokenChange = (e: ChangeEvent<HTMLInputElement>): void => {
         this.setState({
             token: e.target.value,
         });
     };
 
-    private onFormSubmit = async (e: FormEvent) => {
+    private onFormSubmit = async (e: FormEvent): Promise<void> => {
         e.preventDefault();
         if (this.state.token == "") return;
 
@@ -646,7 +646,7 @@ export class MsisdnAuthEntry extends React.Component<IMsisdnAuthEntryProps, IMsi
         }
     };
 
-    public render() {
+    public render(): JSX.Element {
         if (this.state.requestingToken) {
             return <Spinner />;
         } else {
@@ -729,11 +729,11 @@ export class SSOAuthEntry extends React.Component<ISSOAuthEntryProps, ISSOAuthEn
         };
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(SSOAuthEntry.PHASE_PREAUTH);
     }
 
-    public componentWillUnmount() {
+    public componentWillUnmount(): void {
         window.removeEventListener("message", this.onReceiveMessage);
         if (this.popupWindow) {
             this.popupWindow.close();
@@ -741,13 +741,13 @@ export class SSOAuthEntry extends React.Component<ISSOAuthEntryProps, ISSOAuthEn
         }
     }
 
-    public attemptFailed = () => {
+    public attemptFailed = (): void => {
         this.setState({
             attemptFailed: true,
         });
     };
 
-    private onReceiveMessage = (event: MessageEvent) => {
+    private onReceiveMessage = (event: MessageEvent): void => {
         if (event.data === "authDone" && event.origin === this.props.matrixClient.getHomeserverUrl()) {
             if (this.popupWindow) {
                 this.popupWindow.close();
@@ -756,7 +756,7 @@ export class SSOAuthEntry extends React.Component<ISSOAuthEntryProps, ISSOAuthEn
         }
     };
 
-    private onStartAuthClick = () => {
+    private onStartAuthClick = (): void => {
         // Note: We don't use PlatformPeg's startSsoAuth functions because we almost
         // certainly will need to open the thing in a new tab to avoid losing application
         // context.
@@ -766,11 +766,11 @@ export class SSOAuthEntry extends React.Component<ISSOAuthEntryProps, ISSOAuthEn
         this.props.onPhaseChange(SSOAuthEntry.PHASE_POSTAUTH);
     };
 
-    private onConfirmClick = () => {
+    private onConfirmClick = (): void => {
         this.props.submitAuthDict({});
     };
 
-    public render() {
+    public render(): JSX.Element {
         let continueButton = null;
         const cancelButton = (
             <AccessibleButton
@@ -834,24 +834,24 @@ export class FallbackAuthEntry extends React.Component<IAuthEntryProps> {
         window.addEventListener("message", this.onReceiveMessage);
     }
 
-    public componentDidMount() {
+    public componentDidMount(): void {
         this.props.onPhaseChange(DEFAULT_PHASE);
     }
 
-    public componentWillUnmount() {
+    public componentWillUnmount(): void {
         window.removeEventListener("message", this.onReceiveMessage);
         if (this.popupWindow) {
             this.popupWindow.close();
         }
     }
 
-    public focus = () => {
+    public focus = (): void => {
         if (this.fallbackButton.current) {
             this.fallbackButton.current.focus();
         }
     };
 
-    private onShowFallbackClick = (e: MouseEvent) => {
+    private onShowFallbackClick = (e: MouseEvent): void => {
         e.preventDefault();
         e.stopPropagation();
 
@@ -859,13 +859,13 @@ export class FallbackAuthEntry extends React.Component<IAuthEntryProps> {
         this.popupWindow = window.open(url, "_blank");
     };
 
-    private onReceiveMessage = (event: MessageEvent) => {
+    private onReceiveMessage = (event: MessageEvent): void => {
         if (event.data === "authDone" && event.origin === this.props.matrixClient.getHomeserverUrl()) {
             this.props.submitAuthDict({});
         }
     };
 
-    public render() {
+    public render(): JSX.Element {
         let errorSection;
         if (this.props.errorText) {
             errorSection = (

src/components/views/auth/LoginWithQR.tsx

@@ -93,7 +93,7 @@ export default class LoginWithQR extends React.Component<IProps, IState> {
         }
     }
 
-    private async updateMode(mode: Mode) {
+    private async updateMode(mode: Mode): Promise<void> {
         this.setState({ phase: Phase.Loading });
         if (this.state.rendezvous) {
             const rendezvous = this.state.rendezvous;
@@ -150,7 +150,7 @@ export default class LoginWithQR extends React.Component<IProps, IState> {
         }
     };
 
-    private generateCode = async () => {
+    private generateCode = async (): Promise<void> => {
         let rendezvous: MSC3906Rendezvous;
         try {
             const transport = new MSC3886SimpleHttpRendezvousTransport<MSC3903ECDHPayload>({
@@ -190,12 +190,12 @@ export default class LoginWithQR extends React.Component<IProps, IState> {
         }
     };
 
-    private onFailure = (reason: RendezvousFailureReason) => {
+    private onFailure = (reason: RendezvousFailureReason): void => {
         logger.info(`Rendezvous failed: ${reason}`);
         this.setState({ phase: Phase.Error, failureReason: reason });
     };
 
-    public reset() {
+    public reset(): void {
         this.setState({
             rendezvous: undefined,
             confirmationDigits: undefined,
@@ -203,7 +203,7 @@ export default class LoginWithQR extends React.Component<IProps, IState> {
         });
     }
 
-    private onClick = async (type: Click) => {
+    private onClick = async (type: Click): Promise<void> => {
         switch (type) {
             case Click.Cancel:
                 await this.state.rendezvous?.cancel(RendezvousFailureReason.UserCancelled);
@@ -229,7 +229,7 @@ export default class LoginWithQR extends React.Component<IProps, IState> {
         }
     };
 
-    public render() {
+    public render(): JSX.Element {
         return (
             <LoginWithQRFlow
                 onClick={this.onClick}

src/components/views/auth/LoginWithQRFlow.tsx

@@ -45,14 +45,14 @@ export default class LoginWithQRFlow extends React.Component<IProps> {
         super(props);
     }
 
-    private handleClick = (type: Click) => {
-        return async (e: React.FormEvent) => {
+    private handleClick = (type: Click): ((e: React.FormEvent) => Promise<void>) => {
+        return async (e: React.FormEvent): Promise<void> => {
             e.preventDefault();
             await this.props.onClick(type);
         };
     };
 
-    private cancelButton = () => (
+    private cancelButton = (): JSX.Element => (
         <AccessibleButton data-testid="cancel-button" kind="primary_outline" onClick={this.handleClick(Click.Cancel)}>
             {_t("Cancel")}
         </AccessibleButton>
@@ -69,7 +69,7 @@ export default class LoginWithQRFlow extends React.Component<IProps> {
         );
     };
 
-    public render() {
+    public render(): JSX.Element {
         let title = "";
         let titleIcon: JSX.Element | undefined;
         let main: JSX.Element | undefined;

src/components/views/auth/PassphraseConfirmField.tsx

@@ -56,7 +56,7 @@ class PassphraseConfirmField extends PureComponent<IProps> {
         ],
     });
 
-    private onValidate = async (fieldState: IFieldState) => {
+    private onValidate = async (fieldState: IFieldState): Promise<IValidationResult> => {
         const result = await this.validate(fieldState);
         if (this.props.onValidate) {
             this.props.onValidate(result);
@@ -65,7 +65,7 @@ class PassphraseConfirmField extends PureComponent<IProps> {
         return result;
     };
 
-    public render() {
+    public render(): JSX.Element {
         return (
             <Field
                 id={this.props.id}

src/components/views/auth/PassphraseField.tsx

@@ -53,7 +53,7 @@ class PassphraseField extends PureComponent<IProps> {
             const score = complexity ? complexity.score : 0;
             return <progress className="mx_PassphraseField_progress" max={4} value={score} />;
         },
-        deriveData: async ({ value }) => {
+        deriveData: async ({ value }): Promise<zxcvbn.ZXCVBNResult> => {
             if (!value) return null;
             const { scorePassword } = await import("../../../utils/PasswordScorer");
             return scorePassword(value);
@@ -66,7 +66,7 @@ class PassphraseField extends PureComponent<IProps> {
             },
             {
                 key: "complexity",
-                test: async function ({ value }, complexity) {
+                test: async function ({ value }, complexity): Promise<boolean> {
                     if (!value) {
                         return false;
                     }
@@ -94,7 +94,7 @@ class PassphraseField extends PureComponent<IProps> {
         ],
     });
 
-    public onValidate = async (fieldState: IFieldState) => {
+    public onValidate = async (fieldState: IFieldState): Promise<IValidationResult> => {
         const result = await this.validate(fieldState);
         if (this.props.onValidate) {
             this.props.onValidate(result);
@@ -102,7 +102,7 @@ class PassphraseField extends PureComponent<IProps> {
         return result;
     };
 
-    public render() {
+    public render(): JSX.Element {
         return (
             <Field
                 id={this.props.id}

src/components/views/auth/PasswordLogin.tsx

@@ -54,7 +54,7 @@ interface IState {
     password: "";
 }
 
-enum LoginField {
+const enum LoginField {
     Email = "login_field_email",
     MatrixId = "login_field_mxid",
     Phone = "login_field_phone",
@@ -85,13 +85,13 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         };
     }
 
-    private onForgotPasswordClick = (ev) => {
+    private onForgotPasswordClick = (ev): void => {
         ev.preventDefault();
         ev.stopPropagation();
         this.props.onForgotPasswordClick();
     };
 
-    private onSubmitForm = async (ev) => {
+    private onSubmitForm = async (ev): Promise<void> => {
         ev.preventDefault();
 
         const allFieldsValid = await this.verifyFieldsBeforeSubmit();
@@ -117,33 +117,33 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         this.props.onSubmit(username, phoneCountry, phoneNumber, this.state.password);
     };
 
-    private onUsernameChanged = (ev) => {
+    private onUsernameChanged = (ev): void => {
         this.props.onUsernameChanged(ev.target.value);
     };
 
-    private onUsernameBlur = (ev) => {
+    private onUsernameBlur = (ev): void => {
         this.props.onUsernameBlur(ev.target.value);
     };
 
-    private onLoginTypeChange = (ev) => {
+    private onLoginTypeChange = (ev): void => {
         const loginType = ev.target.value;
         this.setState({ loginType });
         this.props.onUsernameChanged(""); // Reset because email and username use the same state
     };
 
-    private onPhoneCountryChanged = (country) => {
+    private onPhoneCountryChanged = (country): void => {
         this.props.onPhoneCountryChanged(country.iso2);
     };
 
-    private onPhoneNumberChanged = (ev) => {
+    private onPhoneNumberChanged = (ev): void => {
         this.props.onPhoneNumberChanged(ev.target.value);
     };
 
-    private onPasswordChanged = (ev) => {
+    private onPasswordChanged = (ev): void => {
         this.setState({ password: ev.target.value });
     };
 
-    private async verifyFieldsBeforeSubmit() {
+    private async verifyFieldsBeforeSubmit(): Promise<boolean> {
         // Blur the active element if any, so we first run its blur validation,
         // which is less strict than the pass we're about to do below for all fields.
         const activeElement = document.activeElement as HTMLElement;
@@ -192,7 +192,7 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         return Object.values(this.state.fieldValid).every(Boolean);
     }
 
-    private findFirstInvalidField(fieldIDs: LoginField[]) {
+    private findFirstInvalidField(fieldIDs: LoginField[]): Field | null {
         for (const fieldID of fieldIDs) {
             if (!this.state.fieldValid[fieldID] && this[fieldID]) {
                 return this[fieldID];
@@ -201,7 +201,7 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         return null;
     }
 
-    private markFieldValid(fieldID: LoginField, valid: boolean) {
+    private markFieldValid(fieldID: LoginField, valid: boolean): void {
         const { fieldValid } = this.state;
         fieldValid[fieldID] = valid;
         this.setState({
@@ -221,13 +221,13 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         ],
     });
 
-    private onUsernameValidate = async (fieldState) => {
+    private onUsernameValidate = async (fieldState): Promise<IValidationResult> => {
         const result = await this.validateUsernameRules(fieldState);
         this.markFieldValid(LoginField.MatrixId, result.valid);
         return result;
     };
 
-    private onEmailValidate = (result: IValidationResult) => {
+    private onEmailValidate = (result: IValidationResult): void => {
         this.markFieldValid(LoginField.Email, result.valid);
     };
 
@@ -235,20 +235,20 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         rules: [
             {
                 key: "required",
-                test({ value, allowEmpty }) {
+                test({ value, allowEmpty }): boolean {
                     return allowEmpty || !!value;
                 },
-                invalid: () => _t("Enter phone number"),
+                invalid: (): string => _t("Enter phone number"),
             },
             {
                 key: "number",
-                test: ({ value }) => !value || PHONE_NUMBER_REGEX.test(value),
-                invalid: () => _t("That phone number doesn't look quite right, please check and try again"),
+                test: ({ value }): boolean => !value || PHONE_NUMBER_REGEX.test(value),
+                invalid: (): string => _t("That phone number doesn't look quite right, please check and try again"),
             },
         ],
     });
 
-    private onPhoneNumberValidate = async (fieldState) => {
+    private onPhoneNumberValidate = async (fieldState): Promise<IValidationResult> => {
         const result = await this.validatePhoneNumberRules(fieldState);
         this.markFieldValid(LoginField.Password, result.valid);
         return result;
@@ -258,21 +258,21 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         rules: [
             {
                 key: "required",
-                test({ value, allowEmpty }) {
+                test({ value, allowEmpty }): boolean {
                     return allowEmpty || !!value;
                 },
-                invalid: () => _t("Enter password"),
+                invalid: (): string => _t("Enter password"),
             },
         ],
     });
 
-    private onPasswordValidate = async (fieldState) => {
+    private onPasswordValidate = async (fieldState): Promise<IValidationResult> => {
         const result = await this.validatePasswordRules(fieldState);
         this.markFieldValid(LoginField.Password, result.valid);
         return result;
     };
 
-    private renderLoginField(loginType: IState["loginType"], autoFocus: boolean) {
+    private renderLoginField(loginType: IState["loginType"], autoFocus: boolean): JSX.Element {
         const classes = {
             error: false,
         };
@@ -295,7 +295,9 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
                         disabled={this.props.busy}
                         autoFocus={autoFocus}
                         onValidate={this.onEmailValidate}
-                        fieldRef={(field) => (this[LoginField.Email] = field)}
+                        fieldRef={(field): void => {
+                            this[LoginField.Email] = field;
+                        }}
                     />
                 );
             case LoginField.MatrixId:
@@ -316,7 +318,9 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
                         disabled={this.props.busy}
                         autoFocus={autoFocus}
                         onValidate={this.onUsernameValidate}
-                        ref={(field) => (this[LoginField.MatrixId] = field)}
+                        ref={(field): void => {
+                            this[LoginField.MatrixId] = field;
+                        }}
                     />
                 );
             case LoginField.Phone: {
@@ -346,14 +350,16 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
                         disabled={this.props.busy}
                         autoFocus={autoFocus}
                         onValidate={this.onPhoneNumberValidate}
-                        ref={(field) => (this[LoginField.Password] = field)}
+                        ref={(field): void => {
+                            this[LoginField.Password] = field;
+                        }}
                     />
                 );
             }
         }
     }
 
-    private isLoginEmpty() {
+    private isLoginEmpty(): boolean {
         switch (this.state.loginType) {
             case LoginField.Email:
             case LoginField.MatrixId:
@@ -363,7 +369,7 @@ export default class PasswordLogin extends React.PureComponent<IProps, IState> {
         }
     }
 
-    public render() {
+    public render(): JSX.Element {
         let forgotPasswordJsx;
 
         if (this.props.onForgotPasswordClick) {

src/components/views/auth/RegistrationForm.tsx

@@ -115,7 +115,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         };
     }
 
-    private onSubmit = async (ev) => {
+    private onSubmit = async (ev): Promise<void> => {
         ev.preventDefault();
         ev.persist();
 
@@ -129,7 +129,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         if (this.state.email === "") {
             if (this.showEmail()) {
                 Modal.createDialog(RegistrationEmailPromptDialog, {
-                    onFinished: async (confirmed: boolean, email?: string) => {
+                    onFinished: async (confirmed: boolean, email?: string): Promise<void> => {
                         if (confirmed) {
                             this.setState(
                                 {
@@ -152,7 +152,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         }
     };
 
-    private doSubmit(ev) {
+    private doSubmit(ev): void {
         PosthogAnalytics.instance.setAuthenticationType("Password");
 
         const email = this.state.email.trim();
@@ -173,7 +173,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         }
     }
 
-    private async verifyFieldsBeforeSubmit() {
+    private async verifyFieldsBeforeSubmit(): Promise<boolean> {
         // Blur the active element if any, so we first run its blur validation,
         // which is less strict than the pass we're about to do below for all fields.
         const activeElement = document.activeElement as HTMLElement;
@@ -231,7 +231,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         return Object.values(this.state.fieldValid).every(Boolean);
     }
 
-    private findFirstInvalidField(fieldIDs: RegistrationField[]) {
+    private findFirstInvalidField(fieldIDs: RegistrationField[]): Field | null {
         for (const fieldID of fieldIDs) {
             if (!this.state.fieldValid[fieldID] && this[fieldID]) {
                 return this[fieldID];
@@ -240,7 +240,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         return null;
     }
 
-    private markFieldValid(fieldID: RegistrationField, valid: boolean) {
+    private markFieldValid(fieldID: RegistrationField, valid: boolean): void {
         const { fieldValid } = this.state;
         fieldValid[fieldID] = valid;
         this.setState({
@@ -248,13 +248,13 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         });
     }
 
-    private onEmailChange = (ev) => {
+    private onEmailChange = (ev): void => {
         this.setState({
             email: ev.target.value.trim(),
         });
     };
 
-    private onEmailValidate = (result: IValidationResult) => {
+    private onEmailValidate = (result: IValidationResult): void => {
         this.markFieldValid(RegistrationField.Email, result.valid);
     };
 
@@ -277,39 +277,39 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         ],
     });
 
-    private onPasswordChange = (ev) => {
+    private onPasswordChange = (ev): void => {
         this.setState({
             password: ev.target.value,
         });
     };
 
-    private onPasswordValidate = (result) => {
+    private onPasswordValidate = (result: IValidationResult): void => {
         this.markFieldValid(RegistrationField.Password, result.valid);
     };
 
-    private onPasswordConfirmChange = (ev) => {
+    private onPasswordConfirmChange = (ev): void => {
         this.setState({
             passwordConfirm: ev.target.value,
         });
     };
 
-    private onPasswordConfirmValidate = (result: IValidationResult) => {
+    private onPasswordConfirmValidate = (result: IValidationResult): void => {
         this.markFieldValid(RegistrationField.PasswordConfirm, result.valid);
     };
 
-    private onPhoneCountryChange = (newVal) => {
+    private onPhoneCountryChange = (newVal): void => {
         this.setState({
             phoneCountry: newVal.iso2,
         });
     };
 
-    private onPhoneNumberChange = (ev) => {
+    private onPhoneNumberChange = (ev): void => {
         this.setState({
             phoneNumber: ev.target.value,
         });
     };
 
-    private onPhoneNumberValidate = async (fieldState) => {
+    private onPhoneNumberValidate = async (fieldState): Promise<IValidationResult> => {
         const result = await this.validatePhoneNumberRules(fieldState);
         this.markFieldValid(RegistrationField.PhoneNumber, result.valid);
         return result;
@@ -334,13 +334,13 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         ],
     });
 
-    private onUsernameChange = (ev) => {
+    private onUsernameChange = (ev): void => {
         this.setState({
             username: ev.target.value,
         });
     };
 
-    private onUsernameValidate = async (fieldState) => {
+    private onUsernameValidate = async (fieldState): Promise<IValidationResult> => {
         const result = await this.validateUsernameRules(fieldState);
         this.markFieldValid(RegistrationField.Username, result.valid);
         return result;
@@ -384,7 +384,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
             {
                 key: "available",
                 final: true,
-                test: async ({ value }, usernameAvailable) => {
+                test: async ({ value }, usernameAvailable): Promise<boolean> => {
                     if (!value) {
                         return true;
                     }
@@ -405,7 +405,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
      * @param {string} step A stage name to check
      * @returns {boolean} Whether it is required
      */
-    private authStepIsRequired(step: string) {
+    private authStepIsRequired(step: string): boolean {
         return this.props.flows.every((flow) => {
             return flow.stages.includes(step);
         });
@@ -417,20 +417,20 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
      * @param {string} step A stage name to check
      * @returns {boolean} Whether it is used
      */
-    private authStepIsUsed(step: string) {
+    private authStepIsUsed(step: string): boolean {
         return this.props.flows.some((flow) => {
             return flow.stages.includes(step);
         });
     }
 
-    private showEmail() {
+    private showEmail(): boolean {
         if (!this.authStepIsUsed("m.login.email.identity")) {
             return false;
         }
         return true;
     }
 
-    private showPhoneNumber() {
+    private showPhoneNumber(): boolean {
         const threePidLogin = !SdkConfig.get().disable_3pid_login;
         if (!threePidLogin || !this.authStepIsUsed("m.login.msisdn")) {
             return false;
@@ -438,7 +438,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         return true;
     }
 
-    private renderEmail() {
+    private renderEmail(): JSX.Element {
         if (!this.showEmail()) {
             return null;
         }
@@ -455,7 +455,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         );
     }
 
-    private renderPassword() {
+    private renderPassword(): JSX.Element {
         return (
             <PassphraseField
                 id="mx_RegistrationForm_password"
@@ -468,7 +468,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         );
     }
 
-    public renderPasswordConfirm() {
+    public renderPasswordConfirm(): JSX.Element {
         return (
             <PassphraseConfirmField
                 id="mx_RegistrationForm_passwordConfirm"
@@ -482,7 +482,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         );
     }
 
-    public renderPhoneNumber() {
+    public renderPhoneNumber(): JSX.Element {
         if (!this.showPhoneNumber()) {
             return null;
         }
@@ -508,7 +508,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         );
     }
 
-    public renderUsername() {
+    public renderUsername(): JSX.Element {
         return (
             <Field
                 id="mx_RegistrationForm_username"
@@ -524,7 +524,7 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         );
     }
 
-    public render() {
+    public render(): JSX.Element {
         const registerButton = (
             <input className="mx_Login_submit" type="submit" value={_t("Register")} disabled={!this.props.canSubmit} />
         );