old_contents: /*eslint no-undef: 2*/
  b = 10; // 'b' is not defined
  
  /*eslint no-unused-vars: "error"*/
  var x = 10; // "x" is defined but never used
  
  (function(foo, bar, baz) { // "baz" is defined but never used
      return bar;
  })();
  
  /*eslint no-use-before-define: "error"*/
  console.log(a);
  var a = 10;
  
  new A();
  class A {
  }
  
  /*eslint no-undefined: "error"*/
  if (foo === undefined) {
      // Use `typeof foo === 'undefined'` instead.
  }
  
new_contents: /*eslint no-undef: 2*/
  b = 10; // 'b' is not defined
  
  /*eslint no-unused-vars: "error"*/
  var x = 10; // "x" is defined but never used
  
  (function(foo, bar, baz) { // "baz" is defined but never used
      return bar;
  })();
  
  /*eslint no-use-before-define: "error"*/
  console.log(a);
  var a = 10;
  
  new A();
  class A {
  }
  
subject: remove `no-undefined` rule