In the official portage tree, I have a package foo with foo-1 and foo-2. In an overlay, I have foo-2, but it's missing a digest, invalidating it. I expected emerge to move to foo-2 of the official tree, but it immediately moves to foo-1. It's debatable, but I'm in favor of the behavior I expected. Thanks for reading!
*** This bug has been marked as a duplicate of bug 262038 ***