False positive for convert function to ES6 class

TypeScript Version: 2.8.0-dev.20180228

Code

function f() {}
f.prototype.bar = function(){
 this.x = 1;
};

Highlight the second function keyword. You will get a suggestion to convert it to an ES6 class -- actually attempting to apply the suggestion does not work.
This happens because apparently the function expression has a non-empty .members containing x.