Implementing conditional conformances alone removed a lot of duplicate code from the standard library. I always like to think that the amount of gyb[^1] files in the source code is a good indicator of how far Swift is in its development.
[1]: gyb, a template processor, is a workaround for features that the standard library needs, but that are not (completely) implemented yet.
[1]: gyb, a template processor, is a workaround for features that the standard library needs, but that are not (completely) implemented yet.