WebStorm reports a "missing import" on built-in objects
<p>I've an ES6 project in WebStorm which obviously sometimes uses some built-in objects like <code>Math</code> or <code>JSON</code>.</p>

<p>Both <em>HTML / ECMAScript 5</em> and <em>ECMAScript 6</em> are enabled in "Settings/(...)/JavaScript/Libraries", yet WebStorm still suggests that <code>Math</code> and <code>JSON</code> are <em>missing imports</em>.</p>

<p>When I create an empty new project it works fine. I also noticed that when selecting <code>JSON</code> in such new project and pressing CTRL+B, WebStorm shows definitions from its internal library.</p>

<p>To the contrary in my main project it shows some TypeScript ones from completely unrelated part of the project. If I move the folder with typescript outside the project it seems to work.</p>

<p>Nota bene, the file I have errors in is not written in TypeScript, does not include anything TypeScript related and is not processed with TypeScript in any way. It is only processed with ES6 to ES5 transpiler.</p>