message: Use a class for default fallback component, as typescript forbids setting a displayName on a `() => Element`.
diff: import * as React from 'react';
  +class DefaultFallback extends React.Component {
  + render () {
  + return <div />;
  + }
  +}
  +
  export class ErrorBoundary extends React.Component<ErrorBoundaryProps, ErrorBoundaryState> {
  constructor(props) {
  super(props);
  @@ -13,7 +19,7 @@ export class ErrorBoundary extends React.Component<ErrorBoundaryProps, ErrorBoun
  }
  render() {
  - const FallbackComponent = this.props.FallbackComponent || (() => <div />);
  + const FallbackComponent = this.props.FallbackComponent || DefaultFallback;
  return this.state.hasError
  ? <FallbackComponent />
  : <div>{this.props.children}</div>;
  