One release of the GHC Haskell compiler, long ago, had a bug where it put all your source files in the list of build artifacts it had created. When GHC ran into

One release of the GHC Haskell compiler, long ago, had a bug where it put all your source files in the list of build artifacts it had created. When GHC ran into a type error, it deleted all its build artifacts from the current run. There are stories told that a few argued to keep it around as a feature for training in doing mental type checking.