Do we call it a Bug?

Question

Alright, suppose a coder left out some part of a program when adding classes to a file.
He writes in all the code but just leaves out a line. The code compiles, runs, and no one has a problem with it for a long time. Then someone brings up the problem of why they can't do this.
Now since the code was fine and it was just the coder simply forgetting to but in some line, would you call it a Bug? Or would you just say it was a mistake or such.

Answer 1

If you are doing quality metrics on your code, it's a bug whose "phase detected" is later than "phase introduced". Which is not a good thing... It is always better for bugs to be detected in the phase in which they were introduced. It is always [or just about always, before someone proves me wrong :) ] cheaper to fix a bug in the phase it was introduced. It causes less rework later. "Phase" here means requirements, design, code, unit test, integration test, system test, fielding, etc. If you find a requirements issue when unit testing, you may have to change design, code, and unit tests. If you had found the requirements issue when still working on requirements, you would only have to change requirements. Good peer reviews are essential all along. Of course, some people who attend peer reviews don't do a good job of reviewing (because they don't try, don't spend the time, don't know how to write good code [or whatever phase this is], etc. in the first place). If you work in a team, you learn which team members are the best reviewers, best coders, best testers, etc. --and the ones who are the opposite, too :(  .