uglify dead code fixed in current release

dead_code.js

define("module", ["exports"], function (exports) {
  "use strict";

  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  var Foo = function Foo() {
    _classCallCheck(this, Foo);
  };

  exports.Foo = Foo;
});

dead_code.md

uglifyjs dead_code.js -c --pure-funcs _classCallCheck

define("module",["exports"],function(exports){"use strict";function _classCallCheck(instance,Constructor){if(!(instance instanceof Constructor)){throw new TypeError("Cannot call a class as a function")}}var Foo=function Foo(){_classCallCheck(this,Foo)};exports.Foo=Foo});

uglifyjs dead_code.js -c negate_iife=false --pure-funcs _classCallCheck

define("module",["exports"],function(exports){"use strict";var Foo=function Foo(){};exports.Foo=Foo});