How to detect returned class in typescript

When I read following nestjs documentation and tried following code.

https://docs.nestjs.com/exception-filters

import { ExceptionFilter, Catch, ArgumentsHost, HttpException } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();

    console.log("ctx",ctx);

    const response = ctx.getResponse<Response>();
    const request = ctx.getRequest<Request>();
    const status = exception.getStatus();

    response
      .status(status)
      .json({
        statusCode: status,
        timestamp: new Date().toISOString(),
        path: request.url,
      });
  }
}

console.log("ctx",ctx); returned following

the type os ExecutionContextHost was returned

ctx ExecutionContextHost {
  args: [
    IncomingMessage {
      _readableState: [ReadableState],
      _events: [Object: null prototype],
      _eventsCount: 1,
      _maxListeners: undefined,
      socket: [Socket],
      httpVersionMajor: 1,
      httpVersionMinor: 1,
      httpVersion: '1.1',
      complete: true,
      headers: [Object],
      rawHeaders: [Array],
      trailers: {},
      rawTrailers: [],
      aborted: false,
      upgrade: false,
      url: '/event',
      method: 'POST',
      statusCode: null,
      statusMessage: null,
      client: [Socket],
      _consuming: true,
      _dumped: false,
      next: [Function: next],
      baseUrl: '',
      originalUrl: '/event',
      _parsedUrl: [Url],
      params: {},
      query: {},
      res: [ServerResponse],
      body: [Object],
      _body: true,
      length: undefined,
      route: [Route],
      [Symbol(kCapture)]: false,
      [Symbol(RequestTimeout)]: undefined
    },
    ServerResponse {
      _events: [Object: null prototype],
      _eventsCount: 1,
      _maxListeners: undefined,
      outputData: [],
      outputSize: 0,
      writable: true,
      destroyed: false,
      _last: false,
      chunkedEncoding: false,
      shouldKeepAlive: true,
      useChunkedEncodingByDefault: true,
      sendDate: true,
      _removedConnection: false,
      _removedContLen: false,
      _removedTE: false,
      _contentLength: null,
      _hasBody: true,
      _trailer: '',
      finished: false,
      _headerSent: false,
      socket: [Socket],
      _header: null,
      _keepAliveTimeout: 5000,
      _onPendingData: [Function: bound updateOutgoingData],
      _sent100: false,
      _expect_continue: false,
      req: [IncomingMessage],
      locals: [Object: null prototype] {},
      statusCode: 201,
      [Symbol(kCapture)]: false,
      [Symbol(kNeedDrain)]: false,
      [Symbol(corked)]: 0,
      [Symbol(kOutHeaders)]: [Object: null prototype]
    },
    [Function: next]
  ],
  constructorRef: null,
  handler: null,
  contextType: 'http',
  getRequest: [Function: getRequest],
  getResponse: [Function: getResponse],
  getNext: [Function: getNext]
}

But when I read ArgumentsHost

https://github.com/nestjs/nest/blob/f472852d/packages/common/interfaces/features/arguments-host.interface.ts#L20

export interface ArgumentsHost {
  getArgs<T extends Array<any> = any[]>(): T;
  getArgByIndex<T = any>(index: number): T;
  switchToRpc(): RpcArgumentsHost;
  switchToHttp(): HttpArgumentsHost;
  switchToWs(): WsArgumentsHost;
}

switchToHttp() method will return HttpArgumentsHost type.

Where ExecutionContextHost come from ?

Why this occured ?

And How can I detect them ?

If someone has opinion, please let me know.

Thanks