old_contents: 
  var app1 = new (require('koa'))(); // HTTP::Server
  
  var Koa = require('koa');
  var app2 = new Koa(); // HTTP::Server
  
  function handler1() {} // HTTP::RouteHandler
  app2.use(handler1);
  
  app2.use(function handler2(ctx){ // HTTP::RouteHandler
    this.set('HEADER1', ''); // HTTP::HeaderDefinition
    this.response.header('HEADER2', '') // HTTP::HeaderDefinition
    ctx.set('HEADER3', ''); // HTTP::HeaderDefinition
    ctx.response.header('HEADER4', '') // HTTP::HeaderDefinition
    var rsp = ctx.response;
    rsp.header('HEADER5', '') // HTTP::HeaderDefinition
  
    ctx.response.body = x // HTTP::ResponseSendArgument
    ctx.request.body;
    ctx.request.query.foo;
    ctx.request.url;
    ctx.request.originalUrl;
    ctx.request.href;
    ctx.request.header.bar;
    ctx.request.headers.bar;
    ctx.request.get('bar');
    ctx.cookies.get('baz');
  });
  
  app2.use(async ctx => {
  	ctx.body = x;
  	ctx.body;
  	ctx.query.foo;
  	ctx.url;
  	ctx.originalUrl;
  	ctx.href;
  	ctx.header.bar;
  	ctx.headers.bar;
  	ctx.set('bar');
  	ctx.get('bar');
  
  	var url = ctx.query.target;
  	ctx.redirect(url);
  	ctx.response.redirect(url);
  });
  
  app2.use(async ctx => {
  	var cookies = ctx.cookies;
  	cookies.get();
  
  	var query = ctx.query;
  	query.foo;
  
  	var headers = ctx.headers;
  	headers.foo;
  });
  
new_contents: 
  var app1 = new (require('koa'))(); // HTTP::Server
  
  var Koa = require('koa');
  var app2 = new Koa(); // HTTP::Server
  
  function handler1() {} // HTTP::RouteHandler
  app2.use(handler1);
  
  app2.use(function handler2(ctx){ // HTTP::RouteHandler
    this.set('HEADER1', ''); // HTTP::HeaderDefinition
    this.response.header('HEADER2', '') // HTTP::HeaderDefinition
    ctx.set('HEADER3', ''); // HTTP::HeaderDefinition
    ctx.response.header('HEADER4', '') // HTTP::HeaderDefinition
    var rsp = ctx.response;
    rsp.header('HEADER5', '') // HTTP::HeaderDefinition
  
    ctx.response.body = x // HTTP::ResponseSendArgument
    ctx.request.body;
    ctx.request.query.foo;
    ctx.request.url;
    ctx.request.originalUrl;
    ctx.request.href;
    ctx.request.header.bar;
    ctx.request.headers.bar;
    ctx.request.get('bar');
    ctx.cookies.get('baz');
  });
  
  app2.use(async ctx => {
  	ctx.body = x;
  	ctx.body;
  	ctx.query.foo;
  	ctx.url;
  	ctx.originalUrl;
  	ctx.href;
  	ctx.header.bar;
  	ctx.headers.bar;
  	ctx.set('bar');
  	ctx.get('bar');
  
  	var url = ctx.query.target;
  	ctx.redirect(url);
  	ctx.response.redirect(url);
  });
  
  app2.use(async ctx => {
  	var cookies = ctx.cookies;
  	cookies.get();
  
  	var query = ctx.query;
  	query.foo;
  
  	var headers = ctx.headers;
  	headers.foo;
  });
  
  var app3 = Koa();
  app3.use(function*(){
  	this.request.url;
  });
  
subject: add koa test