This document summarizes lessons learned from failures in backporting bug fixes to Ruby stable branches: - Don't backport performance improvements or fixes for imaginary use cases as they can introduce regressions. - Be careful backporting fixes related to parsing, constants/method search, and refinements as they are complex and prone to causing new bugs. - Some long-standing bugs may not need fix
![All bugfixes are incompatibilities](https://cdn-ak-scissors.b.st-hatena.com/image/square/1fd22a91bdfe2176b3dc707c339e47fdcdc603a9/height=288;version=1;width=512/https%3A%2F%2Fcdn.slidesharecdn.com%2Fss_thumbnails%2Fallbugfixesareincompatibilities-190421000620-thumbnail.jpg%3Fwidth%3D640%26height%3D640%26fit%3Dbounds)