title: Is it safe to apply autofix from ESLint?
body: <p>I'd like to format several files but I'm worried about <strong>breaking code</strong>. </p>
  
  <p>When I'm saying if it is safe for not, I'm saying that the execution of the code before and after is exactly the same. </p>
  
  <p>For instance, there are rules that look pretty safe to be applied (like indenting). I suppose that changing the number of spaces won't affect the execution of the code.</p>
  
  <p>Then, there are rules that don't look so safe. For instance, changing var to let or const could cause a different execution as var is not exactly the same as let. </p>
  
  <p>So, I'm wondering if there are any auto-fix rule from ESLint that can change the code so the execution is different when applied the <code>--fix</code> thing.</p>